Rozprawy doktorskie: „Silicon Tandem Cells”

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Bett, Alexander Jürgen [Verfasser], i Stefan [Akademischer Betreuer] Glunz. "Perovskite silicon tandem solar cells : : two-terminal perovskite silicon tandem solar cells using optimized n-i-p perovskite solar cells". Freiburg : Universität, 2020. http://d-nb.info/1214179703/34.

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Mirabelli, Alessandro James. "Highly efficient monolithic Perovskite/Silicon bifacial tandem solar cells". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20369/.

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Perovskite solar cells have been the focus of photovoltaics research in this past decade. Owing to their many favorable properties - like low cost solution processability, tunable bandgap and high efficiency, they have seen much attention in various types of solar cell designs. A promising technology has coupled perovskite cells with another semiconductor material in monolithic tandem solar cells, reaching record efficiencies of 29.15%. However, these kinds of devices require current matching condition to maximize the output of solar cells, making their fabrication challenging. Here, we propose the innovative bifacial tandem configuration to overcome current matching limits between the two sub-cells, by collecting photons from the surrounding environment, i.e. albedo. The extra light shining on our silicon bottom cell boosts the photogenerated current above monolithic tandem values. We show that the current density gain is more pronounced in perovskite solar cells with a narrow bandgap, 1.59 eV, than those with a wider one 1.7 eV. In other words, current matched tandems show little to no increase in efficiency with the extra albedo, while mismatched cells exhibit the most power, reaching up to ~28% in the best scenario. To give more credit to our work, we report outdoor data gathered in various locations around the world, and we show how different albedos have distinct effects on bifacial tandems.

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Redorici, Lisa. "Efficiency limits for silicon/perovskite tandem solar cells: a theoretical model". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9531/.

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The primary goal of this work is related to the extension of an analytic electro-optical model. It will be used to describe single-junction crystalline silicon solar cells and a silicon/perovskite tandem solar cell in the presence of light-trapping in order to calculate efficiency limits for such a device. In particular, our tandem system is composed by crystalline silicon and a perovskite structure material: metilammoniumleadtriiodide (MALI). Perovskite are among the most convenient materials for photovoltaics thanks to their reduced cost and increasing efficiencies. Solar cell efficiencies of devices using these materials increased from 3.8% in 2009 to a certified 20.1% in 2014 making this the fastest-advancing solar technology to date. Moreover, texturization increases the amount of light which can be absorbed through an active layer. Using Green’s formalism it is possible to calculate the photogeneration rate of a single-layer structure with Lambertian light trapping analytically. In this work we go further: we study the optical coupling between the two cells in our tandem system in order to calculate the photogeneration rate of the whole structure. We also model the electronic part of such a device by considering the perovskite top cell as an ideal diode and solving the drift-diffusion equation with appropriate boundary conditions for the silicon bottom cell. We have a four terminal structure, so our tandem system is totally unconstrained. Then we calculate the efficiency limits of our tandem including several recombination mechanisms such as Auger, SRH and surface recombination. We focus also on the dependence of the results on the band gap of the perovskite and we calculare an optimal band gap to optimize the tandem efficiency. The whole work has been continuously supported by a numerical validation of out analytic model against Silvaco ATLAS which solves drift-diffusion equations using a finite elements method. Our goal is to develop a simpler and cheaper, but accurate model to study such devices.

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Gugole, Marika. "Development and characterisation of silicon solar cells with recombination interconnects for future tandem solar cells". Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355765.

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In this project commercial BSF Si solar cells have been processed in order to develop a suitable interconnect for a possible tandem solar cell. The Ag original top contacts have been removed and replaced with TiSi2 formed using the SALICIDE process at 3 different temperatures: 500 °C, 650 °C and 750 °C. Raman spectroscopy and EDS maps have been used to prove the successful formation of the TiSi2 contacts for the 750 °C temperature. As part of this work we also developed a MATLAB script which successfully fits the measured IV curve of a Si solar cell and extrapolates the values of the components of the equivalent circuit. The script also identifies and quantifies the energy losses percentage for different loss mechanisms. The script was used to characterize commercial BSF Si solar cells and to simulate their behavior in a tandem configuration by IV measurements under filtered light. The results of this characterization was used to predict the requirements of a possible top solar cell for a tandem configuration.

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Davidson, Lauren Michel. "Strategies for high efficiency silicon solar cells". Thesis, University of Iowa, 2017. https://ir.uiowa.edu/etd/5452.

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The fabrication of low cost, high efficiency solar cells is imperative in competing with existing energy technologies. Many research groups have explored using III-V materials and thin-film technologies to create high efficiency cells; however, the materials and manufacturing processes are very costly as compared to monocrystalline silicon (Si) solar cells. Since commercial Si solar cells typically have efficiencies in the range of 17-19%, techniques such as surface texturing, depositing a surface-passivating film, and creating multi-junction Si cells are used to improve the efficiency without significantly increasing the manufacturing costs. This research focused on two of these techniques: (1) a tandem junction solar cell comprised of a thin-film perovskite top cell and a wafer-based Si bottom cell, and (2) Si solar cells with single- and double-layer silicon nitride (SiNx) anti-reflection coatings (ARC). The perovskite/Si tandem junction cell was modeled using a Matlab analytical program. The model took in material properties such as doping concentrations, diffusion coefficients, and band gap energy and calculated the photocurrents, voltages, and efficiencies of the cells individually and in the tandem configuration. A planar Si bottom cell, a cell with a SiNx coating, or a nanostructured black silicon (bSi) cell can be modeled in either an n-terminal or series-connected configuration with the perovskite top cell. By optimizing the bottom and top cell parameters, a tandem cell with an efficiency of 31.78% was reached. Next, planar Si solar cells were fabricated, and the effects of single- and double-layer SiNx films deposited on the cells were explored. Silicon nitride was sputtered onto planar Si samples, and the refractive index and thicknesses of the films were measured using ellipsometry. A range of refractive indices can be reached by adjusting the gas flow rate ratios of nitrogen (N2) and argon (Ar) in the system. The refractive index and thickness of the film affect where the minimum of the reflection curve is located. For Si, the optimum refractive index of a single-layer passivation film is 1.85 with a thickness of 80nm so that the minimum reflection is at 600nm, which is where the photon flux is maximized. However, using a double-layer film of SiNx, the Si solar cell performance is further improved due to surface passivation and lowered surface reflectivity. A bottom layer film with a higher refractive index passivates the Si cell and reduces surface reflectivity, while the top layer film with a smaller refractive index further reduces the surface reflectivity. The refractive indices and thicknesses of the double-layer films were varied, and current-voltage (IV) and external quantum efficiency (EQE) measurements were taken. The double-layer films resulted in an absolute value increase in efficiency of up to 1.8%.

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Schulze, Patricia S. C. [Verfasser], Harald [Akademischer Betreuer] Hillebrecht i Stefan [Akademischer Betreuer] Glunz. "High band gap perovskite absorbers for application in monolithic perovskite silicon tandem solar cells". Freiburg : Universität, 2020. http://d-nb.info/122336612X/34.

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Komatu, Yuji. "Study on silicon-based tandem solar cells with novel structure towards super high efficiency". Kyoto University, 1997. http://hdl.handle.net/2433/202311.

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Zafoschnig, Lisa Anna. "SnOx electron selective layers for perovskite/silicon tandem solar cells using atomic layer deposition". Thesis, KTH, Energiteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-245992.

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In this work the application of ALD deposited SnOx films as electron transport layers in perovskite solar cells is analysed. Processes to fabricate homogeneous, transparent and conductive tin oxide films were developed on an Oxford Instruments FlexAL tool using a TDMASn precursor and H2O as oxidiser. Two process regimes were investigated; an ALD regime, where the precursor gases are fully separated by long purging steps and a pulsed-CVD regime, where short purge times allow for continuous reactions. Both process regimes were analysed at deposition temperatures from 100 – 250°C and showed a decrease in growth rate with an increase in refractive index for higher temperatures. In terms, of optical properties highly transparent films in the visible range (> 80%) were obtained for all analysed processes. The samples with the lowest absorption were SnOx films deposited at low temperatures in the pulsed-CVD regime. Films with low absorption also exhibited improved conductivity in the range of 200 – 500 Ωcm, which decreased further when the samples were heated. All investigated films were amorphous with a tin rich atomic composition of SnOx. The processes were performed to be compatible with n-i-p and inverted perovskite single junction solar cells as well as tandem devices on textured silicon bottom cells, due to conformal coating at low deposition temperatures and no need for thermal annealing steps. For the application on cell level, perovskite single junction solar cells in a n-i-p architecture were fabricated with a ~15 nm SnOx film as electron transport layer. To improve electron extraction properties different organic interlayers and mesoporous TiO2 were investigated below the perovskite absorber. It was seen that the use of PCBM on top of SnOx improved the solar cell performance of devices with a co-evaporated MAPbI3 absorber. Solar cells with efficiencies close to 6% were fabricated which exhibited a moderately high Voc of ~990 mV but low Jsc of < 10 mA/cm². For devices with wet-chemically deposited perovskite absorber materials, the fullerene solutions did not form a closed film due to wettability issues on SnOx and the risk of washing away by the spin-coated perovskite solution. SEM-images confirmed that no closed interlayers were formed in the wet-chemical devices which could be the cause of poor reproducibility for devices with a planar structure and SnOx as electron contact. The best performing device was achieved with SnOx and mesoporous TiO2 deposited by spin-coating and a MAPbI3 absorber. It showed a mean PCE from forward and reverse scans of 12.8% with a Voc > 990 mV and a Jsc close to 20 mA/cm². Compared to the TiO2 reference cells the devices using SnOx showed lower efficiencies but improved reproducibility and reduced hysteresis in the mesoporous structure. The produced cells serve as an initial proof of concept for the use of SnOx by ALD in the analysed solar cell structure. To analyse the potential for commercialisation of perovskite based photovoltaic technologies a techno-economic analysis was performed. Taking into account up-scaled manufacturing processes for perovskite modules, manufacturing costs of 21.0 $/m² were calculated. This cost is below the calculated allowed extra costs for the top cell of a tandem device with 30 % efficiency, estimated at 30 – 80 $/m². Projections of the LCOE showed that perovskite single junction cells with a PCE of 15% and a lifetime of 25 years could achieve an LCOE of 5.2 c/kWh. For two-terminal tandem devices with a similar lifetime and an efficiency of 27% an LCOE of 6.6 c/kWh could potentially be achieved, making both technologies competitive with conventional energy technologies in Germany. An overview of literature on life cycle assessments showed that despite the use of lead based absorber materials, perovskite technologies have a minor environmental impact and are considered more sustainable than other photovoltaic technologies.
A I detta arbete appliceringen av ALD deponerade SnOx lager som selektiv kontakt till elektronerna perovskite solceller är analyserad. Processer för att fabricera homogena, transparenta och ledande SnOx lager utvecklades med en Oxford Instruments FlexAL med användnig av TDMASn gas och H2O. Två typer av processer analyserades; en ALD process, där dem reaktiva gaser är helt sepererade av långa rensande steg och en pulsed-CVD process, där korta rensningstider tillåter kontinuerliga reaktioner. Båda processer analyserades vid despositionstemperaturer från 100 till 250°C och visade en minsknig i tillväxtakten med en ökning i refractive index för högre temperaturer. Gällande optiska egenskaper, väldigt transparenta lager i det synliga området (> 80%) blev erhållna för alla analyserade processer. De proven med den lägsta absorptionen var SnOx filmer vid låga temperaturer i pulsed – CDV regimer. Lager med en låg absorption uppvisade ochså förbättrad ledningsförmåga inom intervaller från 200 – 500 Ωcm, som minskade ännu mer när proven blev uppvärmda. Alla utrettade lager var amorfisk med en hög andel tenn i SnOx. Procceserna genomfördes för att vara kompatibel med n-i-p och p-i-n perovskite solceller samt tandem apparater på texturerad kisel bottenceller, på grund av enhetlig beläggning vid låga depositionstemperaturer och inget behov av termisk behandling i efterhand. För applikationen på cellnivå, perovskite solceller i en n-i-p konstruktion tillverkades med ett ~15 nm SnOx lager som selektiv kontakt till elektronerna. För att förbättra kontakten olika naturliga mellanskikter och mesoporös TiO2 undersöktes under det perovskite lagret. Det sågs att användnigen av PCBM på SnOx förbättrade funktionen av solcellerna av apparater med en dunstad MAPbI3 absorbator. Solceller med effektivitet nära 6% tillverkades, som ledde till en medelmåttligt hög Voc vid ~990 mV men låg Jsc vid < 10 mA/cm². För apparater med perovskite deponerade vid spin-coating, fullerene-lösningen bildade inget stängt lager på grund av vätningsproblem på SnOx och risken att tvätta bort den spin-coated perovskite lösningen. SEM-bilder bekräftade att inga stängda mellanskikter bildades i dem våtkemiska apparater. Det skulle kunna vara grunden till den dåliga reproducerbarheten av apparater med en platt struktur och SnOx som selektiv kontakt till elektronerna. Den apparaten som uppträdde bäst uppnåddes med SnOx och mesoporös TiO2 deponerade vid spin-coating och en MAPbI3 absorbator. Det visade en genomsnittlig verkningsgrad av 12,8% med Voc > 990 mV och Jsc nära 20 mA/cm². I jämförelse med TiO2 referensceller, dem apparatener som använde SnOx visade lägra effektivitet men förbättrat reproducerbarhet och minskad hysteresis i den mesoporösa strukturen. Dem producerade celler tjäna som första bevis av konceptet för användningen av SnOx vid ALD i den analyserade strukturen av solcellerna. För att analysera potentialen av kommersialiseringen av perovskite baserade photovoltaiv tekniker en ekonomisk analys genomfördes. Att ta med i beräkning storskalig tillverkningsprocesser till perovskite moduler, tillverkningskostnader vid 21.0 $/m² kalkulerades. Denna kostnad är under dem kalkulerade tillåtna extra kostnader till toppcellen av en tandem apparat med 30% effektivitet, beräknad vid 30 – 80 $/m². Projektioner av LCOE visade att perovskite celler med en verkningsgrad vid 15% och en livstid på 25 år skulle kunna uppnå ett LCOE vid 5.2 c/kWh. Två-terminal tandem apparater men en liknande livstid och en effektivitet vid 27% ett LCOE vid 6.6 c/kWh skulle potentiellt kunna bli uppnått, om man gjorde båda tekniker konkurrenskraftiga med andra energitekniker i Tyskland. En översikt av litteratur om livscykelanalyser visade att, trots användningen av blybaserad absorbtionsmaterial, perovskite tekniker har en låg miljöpåverkan och anses vara mer hållbart än andra foltovoltaisk tekniker.

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Dai, Letian. "Silicon nanowire solar cells with μc-Si˸H absorbers for tandem radial junction devices". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS303.

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Dans cette thèse, nous avons fabriqué des cellules solaires à jonction radiale en nanofils de silicium avec du silicium microcristallin hydrogéné (µc-Si:H) comme absorbeur, par dépôt chimique en phase vapeur assisté par plasma à basse température (PECVD). Pour contrôler la densité de nanofils sur les substrats, nous avons utilisé des nanoparticules (NP) de dioxyde d'étain (SnO₂) d'un diamètre moyen de 55 nm, disponibles dans le commerce, comme précurseur du catalyseur Sn pour la croissance des nanofils de silicium. La distribution des nanoparticules de SnO₂ sur le substrat a été contrôlée par centrifugation et dilution du colloïde de SnO₂, en combinaison avec la fonctionnalisation du substrat. Par la suite, le SnO₂ est réduit en Sn métallique après le traitement par plasma de H₂, suivi de la croissance, par la technique vapeur-liquide-solide (VLS) assistée par plasma, de nanofils de Si sur lesquels sont déposées les couches P, I et N constituant les cellules solaires à jonction radiale. Nous avons atteint un taux de croissance élevé des nanofils de Si, jusqu'à 70%, avec une très large gamme de densité, de 10⁶ à 10⁹ /cm². Comme approche supplémentaire de contrôle de la densité des nanofils, nous avons utilisé du Sn évaporé comme précurseur du catalyseur Sn. Nous avons étudié l'effet de l'épaisseur de Sn évaporé, l'effet de la durée du traitement au plasma de H₂ et l'effet du débit de gaz H₂ dans le dans le mélange de précurseurs, sur la densité des nanofils. L'ellipsométrie spectroscopique in-situ (SE) a été utilisée pour contrôler la croissance des nanofils et le dépôt des couches de µc-Si:H sur les SiNWs. En combinant les résultats de in-situ SE et de microscopie électronique à balayage, une relation entre l'intensité du signal de SE pendant la croissance et la longueur et la densité des nanofils a été démontrée, ce qui permet d'estimer ces paramètres en cours de croissance. Nous avons réalisé une étude systématique des matériaux (couches intrinsèques et dopées de type n ou p de µc-Si:H, couches dopées d'oxyde de silicium microcristallin hydrogéné, µcSiOx:H) et des cellules solaires obtenues dans deux réacteurs à plasma appelés "PLASFIL" et "ARCAM". Les épaisseurs de revêtement sur substrat lisse et sur les nanofils ont été déterminées et nous avons obtenu une relation linéaire entre les deux, ce qui permet de concevoir un revêtement conforme sur les nanofils pour chaque couche avec une épaisseur optimale. Les paramètres des nanofils et des matériaux, affectant la performance des cellules solaires à jonction radiale, ont été systématiquement étudiés, les principaux étant la longueur et la densité des nanofils, l'épaisseur de la couche intrinsèque de µc-Si:H, l'utilisation de µc-SiOx:H et le réflecteur arrière en Ag. Enfin, avec les cellules solaires à jonction radiale en nanofils de silicium optimisées utilisant le µc-Si:H comme absorbeur, nous avons atteint un rendement de conversion de l'énergie de 4,13 % avec Voc = 0,41 V, Jsc = 14,4 mA/cm² et FF = 69,7%. Cette performance est supérieure de plus de 40 % à l'efficacité record de 2,9 % publiée précédemment
In this thesis, we have fabricated silicon nanowire (SiNW) radial junction solar cells with hydrogenated microcrystalline silicon (μc-Si:H) as the absorber via low-temperature plasma-enhanced chemical vapor deposition (PECVD). To control the density of NW on the substrates, we have used commercially available tin dioxide (SnO₂) nanoparticles (NPs) with an average diameter of 55 nm as the precursor of Sn catalyst for the growth of SiNWs. The distribution of SnO₂ NPs on the substrate has been controlled by centrifugation and the dilution of the SnO₂ colloid, combined with the functionalization of the substrate. Subsequently, SnO₂ is reduced to metallic Sn after the H₂ plasma treatment, followed by the plasma-assisted vapor-liquid-solid (VLS) growth of SiNWs upon which the P, I and N layers constituting the radial junction solar cells are deposited. We have achieved a high yield growth of SiNWs up to 70% with a very wide range of NW density, from 10⁶ to 10⁹ /cm². As an additional approach of controlling the density of SiNWs we have used evaporated Sn as the precursor of Sn catalyst. We have studied the effect of the thickness of evaporated Sn, the effect of duration of H₂ plasma treatment and the effect of H₂ gas flow rate in the plasma, on the density of SiNWs.In-situ spectroscopic ellipsometry (SE) was used for monitoring the growth of SiNWs and the deposition of the layers of μc-Si:H on SiNWs. Combining in-situ SE and SEM results, a relationship between the intensity of SE signal and the length and the density of SiNWs during the growth was demonstrated, which allows to estimate the density and the length of SiNWs during the growth. We have carried out a systematic study of materials (intrinsic, p-type,n-type µc-Si:H and µcSiOx:H doped layers) and solar cells obtained in two plasma reactors named “PLASFIL” and “ARCAM”. The thicknesses of coating on the flat substrate and on the SiNWs have been determined with a linear relation which helps to design a conformal coating on SiNWs for each layer with an optimal thickness. The parameters of the SiNWs and the materials, affecting the performance of radial junction solar cells, have been systematically studied, the main ones being the length and the density of SiNWs, the thickness of intrinsic layer of μc-Si:H on SiNWs, the use of the hydrogenated microcrystalline silicon oxide (μc-SiOx:H) and the back reflector Ag. Finally, with the optimized silicon nanowire radial junction solar cells using the μc-Si:H as the absorber we have achieved an energy conversion efficiency of 4.13 % with Voc = 0.41 V, Jsc = 14.4 mA/cm² and FF = 69.7%. This performance is more than 40 % better than the previous published record efficiency of 2.9 %

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Michaud, Amadeo. "III-V / Silicon tandem solar cell grown with molecular beam epitaxy". Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS247.

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Le photovoltaïque terrestre est actuellement largement dominé par des dispositifs à base de Silicium. La limite théorique d’efficacité de photoconversion pour les cellules solaires en silicium est de l’ordre de 29%. Avec des modules photovoltaïques ayant une efficacité de 26.3% sur le marché, la filière Si est à un niveau de maturité avancée et exploite déjà la quasi-totalité du potentiel de ce genre de cellule solaires. Le travail exposé ici traite d’une autre voie d’amélioration de l’efficacité de conversion des dispositifs photovoltaïques. En effet, les cellules solaires tandem, assemblées en empilant plusieurs cellules permettent de dépasser les limites associées aux cellules Si. La complémentarité importante des cellules solaire III-V avec les cellules Si permettrai en théorie d’atteindre plus de 40% d’efficacité. Cette thèse vise à l’élaboration de cellule III-V performante et compatible avec un usage en tandem. Dans un premier temps, l’épitaxie d’alliages phosphures a été étudiée et en particulier l’influence des conditions de croissance sur le GaInP. Une réduction de la pression en phosphore durant la croissance provoque des modulations de composition au sein de l’alliage. La température a un impact significatif sur la valeur de bande interdite qui diminue en augmentant la température. Des caractérisations de photoluminescence ont permis de définir les conditions optimales de croissance en maximisant le signal de luminescence de l’alliage. L’étude a notamment révélé que cru dans les conditions choisies, le GaInP présente moins de défaut et d’états profonds qu’à plus faibles températures de croissance. Enfin la capacité à atteindre des niveaux de dopages élevés dans l’alliage AlGaInP et l’impact de sa composition sur le dopage ont étés étudié. Dans un second temps, la structure des cellules solaires simple jonction GaInP a été optimisée. Nous illustrons l’impact de la passivation de la surface des cellules par AlInP et AlGaInP, ainsi que l’amélioration du photo-courant par l’amincissement de l’émetteur dopé n. L’introduction de couche non-dopée dans la structure ne permit pas de remédier au problème de collection des porteurs constaté dans les cellules. La couche limitant l’efficacité des cellules est composée de p-GaInP. Des caractérisations par Cathodoluminescence et Fluorescence résolue en temps d’échantillons identiques à cette couche ont été menées. Elles ont mis en avant une faible longueur de diffusion des porteurs générés dans le matériau. La comparaison de ces propriétés avec la littérature et celle mesurées pour GaInP épitaxié par MOCVD, indique que l’amélioration de l’efficacité des cellules passe par une augmentation de la mobilité des porteurs au sein du GaInP. Une solution pratique, combinant GaInP et AlGaAs dans une cellule à hétérojonction a été mise en œuvre. Ce type de structure est une autre perspective intéressante à l’avenir puisque des efficacités à l’état de l’art ont été mesurées. Enfin nous avons développé un procédé permettant d’adapter les cellules pour un usage tandem. Les structures sont crues en inversé puis transférées sur verre ou wafer de silicium sans endommager leur performance. Toutefois, des améliorations sont toujours nécessaires pour permettre l’assemblage d’une cellule tandem fonctionnelle. En effet, la non-planéité introduite par les contacts arrières de la cellule III-V cause actuellement des problèmes de collage
Terrestrial photovoltaic is dominated by Silicon based devices. For this type of solar cells, the theory predicts an efficiency limit of 29%. With photovoltaic modules showing 26.6% efficiency already, Silicon-based modules is a mature technology and harvest almost their full potential. In this work, we intend to explore another path toward the enhancement of photovoltaic conversion efficiency. Tandem solar cells that consist in stacking sub-cells, allow to overcome the Si efficiency limit. Since solar cells made of III-V semiconductors are complementary to Silicon solar cells, theory predicts that efficiency above 40% is attainable when combining those types of cells. Here we focus on the elaboration of a performant III-V solar cell, compatible for a tandem use. The first stage of the PhD was to build know-how on phosphide alloys epitaxy with MBE. The influence of the growth conditions on GaInP properties was studied. We noted that composition modulations appear in the alloy when grown with low phosphorus pressure. The growth temperature also impacts the material bandgap, which reduces while increasing the temperature. Photoluminescence characterization served to select the best growth conditions by maximizing the photoluminescence efficiency. We could also highlight that in the conditions chosen, the GaInP exhibits less defect states. AlGaInP alloys are used for passivation purposes in the cells, the influence of the composition of the alloy on the Beryllium doping efficiency was studied. Then GaInP single junction solar cells were fabricated. The different layers composing the cells were optimized. The impact of the front surface passivation with AlGaInP and AlInP was emphasized; improvement of the cell photocurrent by the thinning of the n-doped GaInP layer was also demonstrated. The introduction of a non-intentionally-doped layer in the structure was tested in order to remedy the limits encountered with photocurrent collection. The p-GaInP composing the cells was eventually identified as the limiting factor. In depth characterization of samples mimicking the limiting layer was performed with cathodoluminescence and time-resolved fluorescence. A small diffusion length of the generated carriers was evidenced. Comparison with MOVPE and with literature values suggests that improving the carrier mobility in this layer is the main route to follow for improving of the GaInP cell efficiency. A practical solution was proposed and implemented: we designed a cell combining GaInP and AlGaAs in a heterojunction cell. This structure proves to be very relevant for the project since state of the art photoconversion efficiency of 18.7% was obtained. Finally a process was developed to adapt the III-V solar cells to the tandem configuration. Inverted PV cells structures were grown and transferred on glass or Silicon hosts without degradation of their efficiency. Further improvement of the process is needed to build a full tandem device, in particular the back metallization of the III-V cells must be compatible with the bonding of the cells on the host substrate

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Gasparetto, Jacopo. "Investigation of indium tin oxide-titanium dioxide interconnection layers for perovskite-silicon tandem solar cells". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14230/.

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Per superare i limiti di efficienza delle tradizionali celle al silicio, dovuti alla termalizzazione degli elettroni generati dai fotoni solari più energetici, la comunità scientifica si è recentemente indirizzata verso la tecnologia di celle tandem monolitiche perovskite-silicio. In questo tipo di dispositivi, una cella perovskite viene depositata direttamente su di una cella etero-giunzione al silicio (SHJ) ad alta efficienza e, grazie al suo band gap, assorbe i fotoni più energetici permettendo un efficienza totale maggiore. Le celle perovskite attualmente in fase di studio presso Fraunhofer ISE possiedono un contatto posteriore formato da diossido di titanio (TiO2), mentre il contatto frontale delle celle SHJ è formato tipicamente di indium tin oxide (ITO). In questo lavoro si è studiata la fattibilità di celle solari tandem perovskite-silicio, analizzando dettagliatamente l’interfaccia ITO/TiO2 e la sua resistività. Poiché la resistenza di serie di una cella fotovoltaica, di qualunque natura, è un parametro fortemente limitate per l’efficienza di conversione, è necessario che questi layer di interconnessione abbiano una resistenza più bassa possibile per non causare perdite dovute al trasporto dei portatori di carica. Sono stati preparati campioni con formati da uno stack ITO/TiO2/ITO depositato su un substrato di silicio. Tutti i layer di ITO sono stati depositati tramite sputtering mentre sono state testate tre differenti tecniche di deposizione per il TiO2: Electron Beam Physical Vapour Deposition (EBPVD), Thermal Atomic Layer Deposition (T-ALD) e Plasma Enhanced ALD (PE-ALD). Per ogni tecnica di deposizione del TiO2 si è studiata la resistenza dei film, anche in seguito a trattamenti termici a differenti condizioni. Sono state inoltre condotte analisi di diffrazione a raggi X (XRD) e spettroscopia fotoelettronica a raggi X (XPS) per sondare la struttura cristallina e la composizione chimica dei layer di TiO2 depositati su ITO tramite le differenti tecniche.

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Mailoa, Jonathan P. "Beyond the Shockley-Queisser limit : intermediate band and tandem solar cells leveraging silicon and CdTe technology". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105950.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis. Page 156 blank.
Includes bibliographical references (pages 141-153).
The efficiencies of single-junction solar cells have been rapidly increasing and approaching their fundamental Shockley-Queisser efficiency limits. This is true for mature commercial technologies such as silicon and cadmium telluride. In order to enable solar cells with higher efficiency limits, new concepts need to be implemented which overcome the fundamental energy conversion mechanism limitations of single-junction solar cells. For this approach to be successful, it is advantageous to leverage existing manufacturing facilities and integrate these new solar cell architectures into commercially successful solar cell technologies such as silicon and cadmium telluride. In this thesis, two novel solar cell concepts are explored, categorized into three contributions. First, the application of intermediate band concept on silicon solar cells is explored by hyperdoping silicon, demonstrating room-temperature sub-band gap optoelectronic response from the material, and evaluating the feasibility of the intermediate band approach for improving silicon solar cell efficiency. Second, perovskite solar cells are integrated onto silicon solar cells to demonstrate mechanically-stacked perovskite/silicon tandem solar cell using low-cost silicon cell and monolithic perovskite/silicon tandem solar cell enabled by a silicon tunnel junction. Third, an analytic model is built to rapidly investigate the energy yield of different tandem solar cell architectures. When applied to cadmium telluride-based tandem solar cells, this model will help thin-film companies like First Solar narrow down the scope of future research and development programs on tandem solar cells.
by Jonathan P. Mailoa.
Ph. D.

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Hoffmann, André [Verfasser], Uwe [Akademischer Betreuer] Rau i Ralf B. [Akademischer Betreuer] Wehrspohn. "Light management by intermediate reflectors in silicon-based tandem solar cells / André Hoffmann ; Uwe Rau, Ralf B. Wehrspohn". Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://nbn-resolving.de/urn:nbn:de:hbz:82-rwth-2017-025055.

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Hoffmann, André Verfasser], Uwe [Akademischer Betreuer] [Rau i Ralf B. [Akademischer Betreuer] Wehrspohn. "Light management by intermediate reflectors in silicon-based tandem solar cells / André Hoffmann ; Uwe Rau, Ralf B. Wehrspohn". Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1162845783/34.

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Vettori, Marco. "Growth optimization and characterization of regular arrays of GaAs/AIGaAs core/shell nanowires for tandem solar cells on silicon". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC010/document.

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L'objectif de cette thèse est de réaliser l'intégration monolithique de nanofils (NFs) à base de l’alliage Al0.2Ga0.8As sur des substrats de Si par épitaxie par jets moléculaires via la méthode vapeur-liquide-solide (VLS) auto-assistée et de développer une cellule solaire tandem (TSC) à base de ces NFs.Pour atteindre cet objectif, nous avons tout d'abord étudié la croissance de NFs GaAs, étape clé pour le développement des NFs p-GaAs/p.i.n-Al0.2Ga 0.8As coeur/coquille, qui devraient constituer la cellule supérieure de la TSC. Nous avons montré, en particulier, l'influence de l'angle d'incidence du flux de Ga sur la cinétique de croissance des NFs GaAs. Un modèle théorique et des simulations numériques ont été réalisées pour expliquer ces résultats expérimentaux.Nous avons ensuite utilisé le savoir-faire acquis pour faire croître des NFs p-GaAs/p.i.n-Al0,2Ga0,8As coeur/coquille sur des substrats de Si prêts pour l'emploi. Les caractérisations EBIC réalisées sur ces NFs ont montré qu'ils sont des candidats potentiels pour la réalisation d’une cellule photovoltaïque. Nous avons ensuite fait croître ces NFs sur des substrats de Si patternés afin d'obtenir des réseaux réguliers de ces NFs. Nous avons développé un protocole, basé sur un pré-traitement thermique, qui permet d'obtenir des rendements élevés de NFs verticaux (80-90 %) sur une surface patternée de 0,9 x 0,9 mm2.Enfin, nous avons consacré une partie de notre travail à définir le procédé de fabrication optimal pour la TSC, en concentrant notre attention sur le développement de la jonction tunnel de la TSC, l'encapsulation des NFs et le contact électrique supérieur du réseau de NFs
The objective of this thesis is to achieve monolithical integration of Al0.2Ga0.8As-based nanowires (NWs) on Si substrates by molecular beam epitaxy via the self-assisted vapour-liquid-solid (VLS) method and develop a NWs-based tandem solar cell (TSC).In order to fulfil this purpose, we firstly focused our attention on the growth of GaAs NWs this being a key-step for the development of p-GaAs/p.i.n-Al0.2Ga0.8As core/shell NWs, which are expected to constitute the top cell of the TSC. We have shown, in particular, the influence of the incidence angle of the Ga flux on the GaAs NW growth kinetic. A theoretical model and numerical simulations were performed to explain these experimental results.Subsequently, we employed the skills acquired to grow p-GaAs/p.i.n-Al0.2Ga0.8As core/shell NWs on epi-ready Si substrates. EBIC characterizations performed on these NWs have shown that they are potential building blocks for a photovoltaic cell. We then committed to growing them on patterned Si substrates so as to obtain regular arrays of NWs. We have developed a protocol, based on a thermal pre-treatment, which allows obtaining high vertical yields of such NWs (80-90 %) on patterned Si substrates (on a surface of 0.9 x 0.9 mm2).Finally, we dedicated part of our work to define the optimal fabrication process for the TSC, focusing our attention to the development of the TSC tunnel junction, the NW encapsulation and the top contacting of the NWs

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Onno, A. L. "Growth of III-V solar cells on silicon by Molecular Beam Epitaxy : towards monolithic III-V/Si tandem multijunction devices". Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/10037387/.

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Epitaxial growth of III-V materials on silicon (Si) presents an elegant pathway in order to develop high efficiency III-V/Si multijunction solar cells. Such devices could overcome the 29.4 % efficiency limit inherent to single-junction crystalline silicon (c Si) solar cells while maintaining the comparatively low cost associated with Si substrates. The main challenge of this technology lies in the difference of lattice parameters between Si and suitable III-V materials. This lattice mismatch results in the formation of Threading Dislocations (TDs), which propagate upwards to the active regions of the devices. There, they act as recombination centres, hence reducing the minority carrier lifetime and greatly limiting the performance of the devices. A model has first been developed in order to assess the impact of the Threading Dislocation Density (TDD) on the efficiency of GaAsP/Si dual junction devices. We demonstrate that a TDD below 10^{6} cm^{-2} should be targeted in order to achieve efficiencies over 30 %. 1.7 eV Al_{0.2}Ga_{0.8}As solar cells, with an ideal bandgap for a top cell in III-V/Si dual junction architectures, have then been grown on Si substrates by Molecular Beam Epitaxy (MBE). Direct AlGaAs nucleation has been performed on Si, followed by the growth of Dislocation Filter Layers (DFLs) coupled with Thermal Cycle Annealing (TCA) steps in order to reduce the TDD. Notably, a TDD of 8(±2)×10^{6} cm^{-2} has been demonstrated. However, the performance of the cells is limited by the bulk material quality of the Al_{0.2}Ga_{0.8}As, independently of TDs. An optimisation study of the growth conditions of 1.7 eV Al_{0.22}Ga_{0.78}As solar cells on GaAs has, thus, been carried out, leading to a strong improvement in performance when increasing the growth temperature from 580 °C to 620 °C. In particular, an open-circuit voltage (V_{oc}) of 1212 mV has been demonstrated. Transfer of this improved growth recipe to Si substrates should yield devices with a V_{oc} above 1 V.

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Almosni, Samy. "Growth, structural and electro-optical properties of GaP/Si and GaAsPN/ GaP single junctions for lattice-matched tandem solar cells on silicon". Thesis, Rennes, INSA, 2015. http://www.theses.fr/2015ISAR0010/document.

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Cette thèse se concentre sur la fabrication de cellule solaire IIIN- V sur substrat de GaP (001) et sur la croissance de couche de GaP sur Si (001). Le but est de réaliser des cellules solaires hautes efficacité sur un substrat à faible coût afin de les intégrer dans des centrales solaire photovoltaïque sous concentration. Les principaux résultats obtenus montrent : - L’importance de l’utilisation d’AlGaP en tant que couche de prénucléation pour annihiler les parois d’antiphase à l’interface GaP/ Si (néfaste pour les propriétés optoélectroniques des dispositifs) - De nombreuses similitude entre la croissance de GaAsN et de GaPN ce qui permet d’élaborer une stratégie afin d’optimiser les propriétés optoélectroniques du GaAsPN - De fortes corrélations entre les propriétés optique et éléctriques dans les nitrures dilués - La réalisation préliminaire d’une cellule solaire monojonction sur GaP ayant un rendement encourageant de 2.25% considérant la faible épaisseur de l’absorbeur dans cette cellule (300 nm)
This thesis focuses on optimizing the heterogeneous growth of IIIN- V solar cells on GaP (001) and GaP nanolayers on Si (001). The goal is to build high efficiency solar cells on low-cost substrate for the realization of concentrated photovoltaic powerplant. The main results shows: - AlGaP as prenucleation layer increase the annihilations of anti-phase boundaries at the GaP/Si interface (harmful for the electronic properties of the devices). - Similarities between the growth of GaAsN and GaPN giving strategies to improve the GaAsPN electrical properties - Clear correlations between the optical and electrical properties of dilute nitride solar cells, giving interesting tools to optimize the growth of those materials using optical measurements. - The realization of a GaAsPN solar cell on GaP with a yield of 2.25%. This results is encouraging given the thin GaAsPN absorber used in this cell

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Towfie, Nazley. "Dynamic variation of hydrogen dilution during hot-wire chemical vapour deposition of silicon thin films". Thesis, University of the Western Cape, 2013. http://hdl.handle.net/11394/3813.

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It has been debated that among all the renewable energy alternatives, only solar energy offers sufficient resources to meet energy demands. Silicon thin film solar cells are at the frontier of commercial solar technology. Hot wire chemical vapour deposition (HWCVD) is the technique of choice for silicon thin film deposition due to the absence of ion bombardment and its independence toward geometry or electromagnetic properties of the substrate, as seen by plasma enhanced chemical vapour deposition (PECVD). With the implementation of nanostructures in a multi-band gap tandem solar cell, considerable improvement has been achieved over the single junction solar cells. Defect assisted tunnelling processes at the junctions between individual solar cells in a tandem structure solar cell largely affect the efficiency of these solar cells. In this contribution, the investigation toward the improvement of silicon thin films for tandem solar cell application is initiated. This study reports on the effects of hydrogen dilution and deposition time on six silicon thin films deposited at six specific deposition regimes. The thin film properties are investigated via X-Ray diffraction analysis, Raman spectroscopy, Fourier transform infra-red spectroscopy, elastic recoil detection analysis, scanning and transmission electron microscopy and UV-visible spectroscopy. This investigation revealed the dominating etching effect of atomic hydrogen with the increase in hydrogen dilution and a bonded hydrogen content (CH) exceeding 10 at.% for each of the six thin films. The optically determined void volume fraction and static refractive index remain constant, for each thin film, with the change in CH. A new deposition procedure, utilising the deposition conditions of the previously investigated thin films, is performed by HWCVD to deposit two silicon thin films. This deposition procedure involved either increasing (protocol 1) or decreasing (protocol 2) hydrogen dilution during deposition. Structural and optical variation with depth was observed for the dynamically deposited silicon thin films, with nano-voids existing across the entire cross section and bond angle variations which are indicative of good structural order. The optical absorption curves differ for the two silicon thin films whereas the optical density remains constant for both.
>Magister Scientiae - MSc

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Wagner, Philipp [Verfasser], Bernd [Akademischer Betreuer] Rech, Bernd [Gutachter] Rech, Bert [Gutachter] Stegemann i Olindo [Gutachter] Isabella. "Interdigitated back-contact silicon heterojunction solar cells: development of patterning techniques and applications in tandem devices / Philipp Wagner ; Gutachter: Bernd Rech, Bert Stegemann, Olindo Isabella ; Betreuer: Bernd Rech". Berlin : Technische Universität Berlin, 2021. http://d-nb.info/1227989962/34.

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Kegelmann, Lukas [Verfasser], Dieter [Akademischer Betreuer] Neher, Bernd [Akademischer Betreuer] Rech, Rutger [Akademischer Betreuer] Schlatmann, Dieter [Gutachter] Neher, Bernd [Gutachter] Rech, List-Kratochvil [Gutachter] Emil, Reimund [Gutachter] Gerhard i Giovanni [Gutachter] Bruno. "Advancing charge selective contacts for efficient monolithic perovskite-silicon tandem solar cells / Lukas Kegelmann ; Gutachter: Dieter Neher, Bernd Rech, List-Kratochvil Emil, Reimund Gerhard, Giovanni Bruno ; Dieter Neher, Bernd Rech, Rutger Schlatmann". Potsdam : Universität Potsdam, 2019. http://d-nb.info/1218404507/34.

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Michard, Stephan Yann [Verfasser], Uwe [Akademischer Betreuer] Rau i Joachim [Akademischer Betreuer] Knoch. "Relation between growth rate, material quality, and device grade condition for intrinsic microcrystalline silicon : from layer investigation to the application to thin-film tandem solar cells / Stephan Yann Michard ; Uwe Rau, Joachim Knoch". Aachen : Universitätsbibliothek der RWTH Aachen, 2015. http://nbn-resolving.de/urn:nbn:de:hbz:82-rwth-2015-012581.

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Michard, Stephan Yann Verfasser], Uwe [Akademischer Betreuer] [Rau i Joachim [Akademischer Betreuer] Knoch. "Relation between growth rate, material quality, and device grade condition for intrinsic microcrystalline silicon : from layer investigation to the application to thin-film tandem solar cells / Stephan Yann Michard ; Uwe Rau, Joachim Knoch". Aachen : Universitätsbibliothek der RWTH Aachen, 2015. http://d-nb.info/1127739654/34.

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Medjoubi, Karim. "Investigation of new solar cell technology III-V//Si behavior under irradiations for space applications". Thesis, Institut polytechnique de Paris, 2021. http://www.theses.fr/2021IPPAX004.

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Ce travail s’intéresse au comportement en environnement spatial d’une nouvelle technologie de cellules solaires photovoltaïque : les tandems III-V//Si (2- et 3-jonctions), obtenues par collage direct. Ces cellules ont été exposé à des irradiations électrons et protons et testé dans deux type d’environnement : a) irradiance normale, 1 soleil, et température ambiante 300K, condition NIRT (orbites terrestres) et b) basse irradiance, 0,03 soleil, et basse température 120K, condition LILT (espace lointain). Dans une étape préliminaire une étude comparative a été mené sur 2 simulateurs solaires, équipés respectivement d’une lampe flash et de lampes LED, afin d’assurer la fiabilité et la reproductibilité des mesures de ces multi-jonctions. Pour le simulateur flash, une méthode de caractérisation pour tandems I-V sous 1 soleil qui s’affranchit de l’utilisation de cellules de référence isotype a été adoptée, en se basant sur des mesures d’EQE et des mesures du spectre du flash. Pour le simulateur LED, monté in-situ sur le faisceau d’irradiation, une optimisation du spectre a été effectuée afin de se rapprocher de la référence à basse irradiance, soit ~3% AM0. Cette étude comparative a également permis d’établir la validité de l’extrapolation par le calcul de mesures I-V sous 1 soleil vers les basses irradiances.Ensuite, la compatibilité de cette technologie tandem III-V//Si avec d’un part le cyclage thermique et d’autre part les irradiations a été démontrée, l’interface de collage maintient son intégrité mécanique et électrique face à ces contraintes. L’impact des irradiations sur les performances cellules a révélé certaines similitudes à 300 K et 120 K : - une décroissance marquée du courant de court-circuit (liée à la diminution de la longueur de diffusion) - une diminution plus faible de la tension de circuit-ouvert (défauts de type génération). Du fait de la connexion en séries des sous-cellules, la dégradation de la limitante Si (faible résistance intrinsèque aux irradiations) domine le comportement de la multi-jonction. Il a été démontré que l’ajout d’un nombre croissant de cellules sur le Si se traduit par une sensibilité accru aux irradiations; en effet, la configuration tandem restreint la bande d’absorption du Si au proche infrarouge, partie spectrale la plus affectée par la baisse de longueur de diffusion. L’utilisation d’un modèle basé sur l’IQE a permis de quantifier cette dégradation de longueur de diffusion dans le Si en tandem, ainsi que le coefficient de dommage. A la différence des électrons, les irradiation aux protons 1 MeV sont à l’origine d’une dégradation non-uniforme dans le Si ; par des mesures EQE couplées à de la simulation, nous avons corrélé cette dégradation non-homogène dans le Si avec la position du pic de Bragg correspondant.Pour l’étude basse température, une augmentation linéaire de l’efficacité a été observée jusqu’à ~150K ; et en deçà, des anomalies de caractéristiques I-V ont été détectées ; de type « S like shape » et « flat spot » ces défauts affectent le FF et donc le rendement. Documentées dans la littérature, ces effets sont caractéristiques des conditions LILT, et souvent liées à des modifications des interfaces métal/semi-conducteur. Bien qu’importante, la dégradation des performances électriques fin de vie LILT des III-V//Si s’avère être plus prédictible que celles des III-V/Ge LILT (dispersion statistique). Nous avons également démontré qu’un passage à 300 K, après irradiation à 120 K, entraine une guérison marquée du courant de court-circuit; ceci souligne l’importance des caractérisations in-situ pour quantifier le vieillissement cellule en conditions de fonctionnement. L’approche DDD « Displacement Damage Dose » a été appliqué pour les électrons et protons 1 MeV afin de comparer le taux de dégradation induit. Cette approche permet de prédire la dégradation de ces cellules quel que soit la fluence, les particules et l’énergie, pour une mission spatiale à 300 K
This work focuses on the behavior in space environment of a new photovoltaic solar cell technology: the III-V//Si tandems (2- and 3-junction), obtained by direct bonding. These cells have been exposed to electron and proton irradiations and tested in two types of environment: a) normal irradiance, 1 sun, and 300K room temperature, NIRT condition (Earth orbits) and b) low irradiance, 0.03 sun, and 120K low temperature, LILT condition (deep space). In a preliminary stage, a comparative study was conducted on 2 solar simulators, respectively equipped with a flash lamp and LED lamps, in order to ensure the reliability and reproducibility of the measurements of these multi-junctions. For the flash simulator, a tandems characterization method for I-V under 1 sun that dispense the use of isotype reference cells has been adopted, based on EQE and flash spectrum measurements. For the LED simulator, mounted in-situ on the irradiation beam, a spectrum optimization was performed in order to approach the low irradiance reference, i.e. ~3% AM0. This comparative study also allowed to establish the validity of the extrapolation by calculating I-V measurements under 1 sun towards low irradiances.Then, the compatibility of this tandem III-V//Si technology with thermal cycling on the one hand and irradiances on the other hand has been demonstrated. The bonding interface maintains its mechanical and electrical integrity face to these constraints. The impact of the irradiations on the cell performances has revealed certain similarities at 300 K and 120 K: - a marked decrease in the short-circuit current (linked to the decrease in the diffusion length) - a smaller decrease in the open-circuit voltage (generation type defects). Due to the series connection of the sub-cells, the degradation of the limiting Si (low intrinsic resistance to irradiation) dominates the behavior of the multi-junction. It has been shown that the addition of an increasing number of cells on the Si results in an increased sensitivity to irradiation; indeed, the tandem configuration restricts the absorption band of the Si to the near infrared, the spectral part most affected by the decrease in diffusion length. The use of a model based on the IQE allowed the qualification of this diffusion length degradation of the Si in tandem, as well as the damage coefficient. Unlike electrons, 1 MeV proton irradiations are at the origin of a non-homogeneous degradation in Si; by EQE measurements coupled with simulation, we have correlated this non-homogeneous degradation in Si with the position of the corresponding Bragg peak.For the low-temperature study, a linear increase in efficiency was observed up to ~150K; and below this, anomalies of I V characteristics were detected; of "S-like shape" and "flat spot" type, these defects affect the FF and thus the efficiency. Reported in the literature, these effects are characteristic of LILT conditions, and are often related to changes in the metal/semiconductor interfaces. Although significant, the LILT end-of-life electrical performance degradation of III-V//Si has been shown to be more predictable than that of III-V/Ge LILT (statistical dispersion). We have also shown that a 300 K annealing after irradiation at 120 K leads to a marked healing of the short-circuit current; this underlines the importance of in-situ characterizations to quantify cell aging under operating conditions. The Displacement Damage Dose (DDD) approach was applied for 1 MeV electrons and protons in order to compare the rate of induced degradation. This approach allows to predict the degradation of these cells whatever the fluence, particles and energy, for a space mission at 300 K

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Schnabel, Manuel. "Silicon nanocrystals embedded in silicon carbide for tandem solar cell applications". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:da5bbb64-0bcd-4807-a9f3-4ff63a9ca98d.

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Tandem solar cells are potentially much more efficient than the silicon solar cells that currently dominate the market but require materials with different bandgaps. This thesis presents work on silicon nanocrystals (Si-NC) embedded in silicon carbide (SiC), which are expected to have a higher bandgap than bulk Si due to quantum confinement, with a view to using them in the top cell of a tandem cell. The strong photoluminescence (PL) of precursor films used to prepare Si-NC in SiC (Si-NC/SiC) was markedly reduced upon Si-NC formation due to simultaneous out-diffusion of hydrogen that passivated dangling bonds. This cannot be reversed by hydrogenation and leads to weak PL that is due to, and limited by, non-paramagnetic defects, with an estimated quantum yield of ≤5×10^-7. Optical interference was identified as a substantial artefact and a method proposed to account for this. Majority carrier transport was found to be Ohmic at all temperatures for a wide range of samples. Hydrogenation decreases dangling bond density and increases conductivity up to 1000 times. The temperature-dependence of conductivity is best described by a combination of extended-state and variable-range hopping transport where the former takes place in the Si nanoclusters. Furthermore, n-type background doping by nitrogen and/or oxygen was identified. In the course of developing processing steps for Si-NC-based tandem cells, a capping layer was developed to prevent oxidation of Si-NC/SiC, and diffusion of boron and phosphorus in nanocrystalline SiC was found to occur via grain boundaries with an activation energy of 5.3±0.4 eV and 4.4±0.7 eV, respectively. Tandem cells with a Si-NC/SiC top cell and bulk Si bottom cell were prepared that exhibited open-circuit voltages V_oc of 900 mV and short-circuit current densities of 0.85 mAcm^-2. Performance was limited by photocurrent collection in the top cell; however, the V_oc obtained demonstrates tandem cell functionality.

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Chuan, Chen Max. "Fabrication and Characterizationof Low Temperature Annealed Silicon Bottom Cell for CELOGbased Tandem Solar Cell Systems". Thesis, KTH, Tillämpad fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231927.

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Chen, Mas Chuan. "Fabrication and Characterizationof Low Temperature Annealed Silicon Bottom Cell for CELOG based Tandem Solar Cell Systems". Thesis, KTH, Tillämpad fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231540.

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Cavalazzi, Gianmarco. "Fisica delle celle fotovoltaiche modelli e prospettive di ricerca". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24338/.

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La presente tesi costituisce un lavoro di rassegna sugli ultimi risultati e sulle prospettive di ricerca relative alle celle fotovoltaiche. Dopo un’introduzione sulle proprietà di interesse della radiazione elettromagnetica e dello spettro solare, si illustrano i meccanismi fisici di interazione radiazione-materia alla base dell’effetto fotovoltaico. Si descrivono poi il principio di funzionamento e i parametri caratteristici delle celle fotovoltaiche, e si discutono alcune strategie adottate per migliorare l’efficienza di conversione dell’energia solare in energia elettrica. Si presentano infine alcune delle tecnologie e architetture più recenti di celle solari: le celle fotovoltaiche a perovskite e le celle fotovoltaiche tandem silicio-perovskite, che hanno dimostrato grandi potenzialità di miglioramento delle prestazioni e risultano particolarmente interessanti per le elevate efficienze raggiunte e i bassi costi di produzione.

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Huang, Zhiquan. "Spectroscopic Ellipsometry Studies of Thin Film a-Si:H/nc-Si:H Micromorph Solar Cell Fabrication in the p-i-n Superstrate Configuration". University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1460919549.

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Jelena, Ćurčić. "In silico određivanje fizičko-hemijskih, farmakokinetskih i toksikoloških parametara i in vitro ispitivanje antiproliferativne aktivnosti novosintetisanih derivata N-sukcinimida". Phd thesis, Univerzitet u Novom Sadu, Medicinski fakultet u Novom Sadu, 2020. https://www.cris.uns.ac.rs/record.jsf?recordId=113945&source=NDLTD&language=en.

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Sukcinimidi su jedinjenja koja pokazuju višestruke farmakološke efekte uključujući i antiproliferativnu aktivnost, zahvaljujući prisustvu farmakofore sa dva hidrofobna regiona i dva regiona bogata elektronima. Savremeni dizajn lekova ima za cilj da se modifikacijama u strukturi (promena vrste, položaja i orijentacije supstituenata) i in silico računarskim metodama predvide i optimizuju farmakokinetske osobine i bezbednosni profil kandidata za lek. U ranoj fazi razvoja lekova se koriste postojeće baze podataka o molekulskim, farmakokinetskim i toksikološkim parametrima već ispitanih jedinjenja i pomoću matematičkih modela i algoritama predviđaju se osobine novih molekula, eliminišu se neodgovarajući kandidati i postiže se ušteda u vremenu i materijalnim sredstvima. Da se ispitaju fizičko-hemijske karakteristike 11 novosintetisanih metil-etil-N-aril-sukcinimida na osnovu strukture, primenom različitih softverskih paketa; da se na osnovu strukture odrede farmakokinetski i toksikološki parametri, primenom različitih softverskih paketa; da se ispita retenciono ponašanje, odnosno odrede retencione konstante za svako jedinjenje primenom visokoefikasne hromatografije na tankom sloju (HP-TLC) i ispita mogućnost primene retencionih konstanti kao mere lipofilnosti ispitivanih jedinjenja; da se ispita antiproliferativna aktivnost na odabranim kulturama ćelija karcinoma i na zdravim ćelijama fibroblasta pluća; da se analizom molekulskog dokinga ustanovi vezivanje za estrogene receptore. Ispitano je retenciono ponašanje 11 novosintetisanih derivata sukcinimida primenom visokoefikasne hromatografije na tankom sloju (HP-TLC) obrnute faze uz primenu dvokomponentne smeše vode i organskog rastvarača (metanola, acetonitrila ili acetona), sa odgovarajućim zapreminskim udelom organskog rastvarača kao mobilne faze. Iz razvijenih hromatograma su izračunate retencione konstante RM0 i S. Logaritam podeonog koeficijenta (logP) određen je in silico, korišćenjem različitih računarskih programa. In silico su određene fizičko-hemijske karakteristike, farmakokinetski parametri, toksikološki parametri, akvatična toksičnosti i afinitet vezivanja za estrogene receptore. Izračunate su vrednosti afiniteta za 4 vrste receptora (G-protein spregnuti receptori, jonski kanali, inhibitori kinaza, nuklearni receptori). Antiproliferativna aktivnost ispitivanih derivata sukcinimida određena je primenom kolorimetrijskog testa sa tetrazolijum solima (MTT testa) na komercijalnim kulturama ćelija (MRC-5, A549, HeLa, MDA-MB-231, MCF-7, HT-29) i izračunate su IC50 vrednosti. Urađena je i doking analiza sukcinimida prema ERA (estrogen receptor alfa) i ERB (estrogen receptor beta) i dobijene su vrednosti energije formiranja kompleksa sa posmatranim receptorima (MolDock Score). Statistički najznačajnije linearne korelacije dobijene su između eksperimentalno određenih hromatografskih parametara (RM0 i S) i in silico parametara lipofilnosti MlogP i ClogP. Ispitivanjem uticaja promene RM0 i S na farmakokinetske karakteristike dobijeni su rezultati koji pokazuju paraboličnu zavisnost konstante apsorpcije (Ka) i procenta vezivanja za proteine plazme (PPB) od posmatranih retencionih konstanti, dok je zavisnost sa volumenom distribucije (Vd) i sposobnošću prolaska kroz krvno-moždanu barijeru (logBBB) bila linearnog tipa. Toksičnost ispitivanih jedinjenja, procenjena na osnovu in silico dobijenih LD50 vrednosti, nije bila viša od toksičnosti već registrovanih lekova sa strukturom sukcinimida, i dala je parabolične zavisnosti u odnosu na RM0 i S vrednosti. Eksperimentalno nijedno od ispitivanih jedinjenja nije pokazalo aktivnost u odnosu na zdrave fibroblaste pluća. Najznačajniju antiproliferativnu aktivnost (najniže IC50) su pokazala jedinjenja 6 i 7 u odnosu na ćelije linije MCF-7 i jedinjenje 11 u odnosu na A549 ćelijsku liniju. Doking analiza je pokazala niže energije formiranja kompleksa sa ERA, u odnosu na ERB. Eksperimentalno određeni parametri RM0 i S se mogu koristiti kao alternativne i pouzdane mere lipofilnosti analiziranih sukcinimida. Ispitivana jedinjenja pokazuju povoljne fizičko-hemijske karakteristike, predviđene in silico metodama i povoljne farmakokinetske karakteristike: male vrednosti konstante apsorpcije, umeren volumen distribucije, povoljan afinitet vezivanja za proteine plazme, favorizovan prolazak kroz krvno-moždanu barijeru za lipofilnija jedinjenja. Procenjuje se da sva ispitivana jedinjenja, izuzev derivata sa –CN supstituentom, imaju zahtevani nizak stepen toksičnosti. Po antiproliferativnoj aktivnosti u odnosu na ćelije ER-zavisnog karcinoma dojke (MCF-7) izdvajaju se jedinjenja sa metil i nitro supstituentom u para položaju. Na osnovu malih energija formiranja kompleksa sa ERA, koji su eksprimirani na ćelijama MCF-7 linije, pretpostavlja se da bi mehanizam njihovog delovanja delimično mogao biti objašnjen uticajem na ERA, ali su potrebna dodatna istraživanja na tom polju.
Succinimides have exhibited various pharmaceutical effects including antiproliferative activity due to an important structural fragment (a pharmacophore) presented in form of two hydrophobic regions and two electron-rich centers. Current development of new drugs involves modifications in structure (type, position and orientation of substituents) and usage of in silico computational programs to predict and optimize pharmacokinetic and safety profile of drug candidates. In early phase of drug development, databases regarding the molecular, pharmacokinetic and toxicological parameters of already tested compounds are used, mathematical models and algorithms are applied for predicting the properties of new molecules and inadequate candidates are eliminated saving time and resources. Determination of physico-chemical properties of the analyzed methyl-ethyl-N-phenilsuccinimide derivatives by software packages; virtual pharmacokinetic and toxicology screening; investigation of retention behavior of the compounds by the reversed-phase HPTLC analysis and calculation of retention constants and their correlation with lipophilicity; in vitro evaluation of antiproliferative activity toward five carcinoma cell lines and normal fetal lung cell line; molecular behavior study on target estrogen receptors by molecular docking and correlation of antiproliferative activity toward ER+ breast carcinoma cell lines and in silico estrogen receptor affinity binding. Retention behavior of 11 newly synthesized succinimide derivatives was determined by reversed phase high performance thin layer chromatography (RP HPTLC) with the application of two-component mixtures water - organic solvent (methanol, acetonitrile or acetone) with adequate volume fractions of the organic modifier. After chromatographic development RM0 and S parameters were calculated. The logarithm of partition coefficient, logP for the analyzed compounds were calculated by different softwares. Physico-chemical properties, pharmacokinetic and toxicological parameters, aquatic toxicity and relative affinity to estrogen receptors were predicted in silico. The affinity toward 4 types of receptors (G-proteine coupled receptors, ion channels, kinase inhibitors, nuclear receptors) were calculated as well. Standard MTT assay was applied to evaluate cytotoxic activities of the analyzed succinimides after cells were exposed. Antiproliferative activity were investigated toward commercial MRC-5, A549, HeLa, MDA-MB-231, MCF-7, HT-29 cell lines and IC50 values were calculated for each compound. MolDock Score that represents energy of binding to estrogen alfa and estrogen beta receptors was determined by molecular docking. Statistically significant linear correlations were determined between the chromatographic retention constants (RM0 and S) and calculated logP, and the best two were obtained in correlation of retention constants with MlogP and ClogP. The examination of RM0 and S influence on pharmacokinetics indicated parabolic dependence of the absorption constant (Ka) and plasma protein binding predictor (PPB) from the observed constants while the volume of distribution (Vd) and the ability to cross the brain blood barrier (logBBB) had linear association with the retention parameters. The toxicity of the analysed compounds evaluated in silico as LD50 on rodents was lower in comparison with the drugs with succinimide structure that are on the market and had parabolic correlation with the RM0 and S values. The experiments indicated that none of the compounds examined had cytotoxic activity toward the healthy lung fibroblast cells. The results of the in vitro assay shown that none of the investigated compounds demonstrated antiproliferative activity toward fetal lung cells. The most potent antiproliferative agents were compounds 6 and 7 toward MCF-7 cell line, and compound 11 toward A549 cell line. Molecular docking shown lower energy for binding to ERA in comparison to ERB.

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"Silicon-Based Tandem Solar Cells with Silicon Heterojunction Bottom Cells". Doctoral diss., 2018. http://hdl.handle.net/2286/R.I.48464.

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abstract: Silicon photovoltaics (PV) is approaching its theoretical efficiency limit as a single-junction technology. To break this limit and further lower the PV-generated levelized cost of electricity, it is necessary to engineer a silicon-based “tandem” technology in which a solar cell of another material is stacked on top of silicon to make more efficient use of the full solar spectrum. This dissertation understands and develops four aspects of silicon-based tandem PV technology. First, a new “spectral efficiency” concept is proposed to understand how tandem cells should be designed and to identify the best tandem partners for silicon cells. Using spectral efficiency, a top-cell-design guide is constructed for silicon-based tandems that sets efficiency targets for top cells with various bandgaps to achieve targeted tandem efficiencies. Second, silicon heterojunction solar cells are tuned to the near-infrared spectrum to enable world-record perovskite/silicon tandems both in two- and four-terminal configurations. In particular, for the 23.6%-efficient two-terminal tandem, a single-side textured silicon bottom cell is fabricated with a low-refractive-index silicon nanoparticle layer as a rear reflector. This design boosts the current density to 18.5 mA/cm2; this value exceeds that of any other silicon bottom cell and matches that of the top cell. Third, “PVMirrors” are proposed as a novel tandem architecture to integrate silicon cells with various top cells. A strength of the design is that the PVMirror collects diffuse light as a concentrating technology. With this concept, a gallium-arsenide/silicon PVMirror tandem is demonstrated with an outdoor efficiency of 29.6%, with respect to the global irradiance. Finally, a simple and versatile analytical model is constructed to evaluate the cost competitiveness of an arbitrary tandem against its sub-cell alternatives. It indicates that tandems will become increasingly attractive in the market, as the ratio of sub-cell module cost to area-related balance-of-system cost—the key metric that will determine the market success or failure of tandems—is decreasing. As an evolution of silicon technology, silicon-based tandems are the future of PV. They will allow more people to have access to clean energy at ultra-low cost. This thesis defines both the technological and economic landscape of silicon-based tandems, and makes important contributions to this tandem future.
Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2018

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Zin, Ngwe Soe Josh. "Miniature silicon solar cells for a tandem cell stack". Phd thesis, 2010. http://hdl.handle.net/1885/150204.

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The Defence Advanced Research Project Agency (DARPA) of the United States of America sponsors a project aimed at developing a 50% efficient mechanically stacked solar cell based utilising six sub-cells of differing materials. This thesis examines the development of miniature silicon solar (MSS) cells for the tandem stack. The role of the silicon cell in the tandem stack is to absorb photon energy in the range of 1.42 -1.1 eV, and convert up to 7% of the light incident on the tandem stack into electricity. Other cells in the stack contribute the balance of the electricity. Key design parameters for the silicon cells are that it should have dimensions of 2.5 x 8 mm and it needs to transfer light with energy of less than 1.1ev to the underlying solar cells. In designing MSS cells, considerations such as optical losses, optimum diffusions and substrate doping, substrate thickness, free carrier absorption (FCA), internal quantum efficiency (IQE), recombination and resistive losses were taken into account. The approach of increasing the substrate thickness was used in the absence of texturing and back surface reflectors which interfere with transmission of sub-bandgap light to underlying cells. Reducing the doping density in the base and emitter minimises FCA losses. IQE of the MSS cells operating in the infrared spectrum is less affected by relatively heavy emitter doping because of lower absorption coefficients compared with those for the shorter wavelength light present in normal sunlight. Simulation showed that silicon solar cells with an emitter on both front and rear surface have a superior IQE response than for the case of an emitter on the sunward surface only. The use of nitride as an anti-reflection layer -incorporating a thin oxide passivating the silicon -returns the lowest reflection loss as compared to oxide and titanium oxide layers, for silicon solar cells operating in the infrared spectrum, and surrounded by a pottant material with a refractive index of ~1.4. Recombination in the MSS cells occurs at surface, bulk, contacts, junction and edges. Surface recombination is minimised by high-quality thermal oxide passivation. High bulk lifetime was maintained by the use of high-quality float-zone silicon material, and chlorine-assisted oxidation and cleaning. Recombination in the contacts was suppressed by incorporation of heavy diffusion. Edge recombination was suppressed by dicing the cell nearly completely from the host wafer prior to the final passivation step, and by keeping the emitter diffusion at least 1 mm away from the residual cell edge where the dicing occurs during cell detachment. To achieve an adequately high efficiency of silicon solar cells operating in the infrared spectrum various cell design options were considered: single-junction (SJ), horizontally stacked (HS) and vertically stacked (VS). Factors such as suppressing recombination, increasing current, current matching, series or parallel connection, reflection between cell interfaces, resistive losses and fabrication complexity were compared and contrasted for these cell designs. Modelling showed that VS and HS cells could achieve efficiency higher than SJ cells but at the expense of increased fabrication complexity. A single-junction MSS cell design was adopted since it is easier to implement, has adequate performance potential, and does not require current matching. In fabricating the MSS cells, a wide variety of tools were used. These included infrared and green laser machining, Reactive Ion Etching (RIE), Chemical Vapour Deposition, room temperature passivation, Light-induced and Electrolyte Plating, Palladium Silicide for metallisation and a measurement jig that enables testing the cells under the infrared spectrum. Comprehensive characterisation and development of these tools for their efficacy in fabricating MSS cells was undertaken. Analysis of low shunt resistance and carrier lifetime degradation by RIE on the MSS cells was carried out. RIE induces two main types of degradation on samples: permanent and reversible. Reversible degradation is recoverable by annealing the samples in nitrogen ambient, while permanent degradation is avoidable by wet chemical etch and by limiting the area of sample's surface exposed to RIE. Of all shunts, shunting caused by boron diffusion-induced pinholes was found to be most significant in the fabrication of MSS cells. Silicon solar cells fabricated following characterisation of inferior performances caused by shunting and RIE-induced degradation demonstrated a sharply improved performance but were still short of the expected efficiency. Attention then turned to hydrogenation of LPCVD nitride coated samples which are subjected to prolonged high temperature anneals during the fabrication. Hydrogenation of prolonged high- temperature annealed LPCVD nitride coated samples became ineffective due to the densification of LPCVD nitride. Further characterisation revealed that the carrier degradation arising from laser-scribing which affects a relatively large proportion of the volume of the cell, significantly reduced the high efficiency potential of the miniature silicon solar cells for a tandem stack.

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Mehanathan, Nishanth. "Oxide Semiconductors for Silicon Tandem Solar Cells". Thesis, 2017. https://etd.iisc.ac.in/handle/2005/4775.

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In tandem solar cells two or more solar cells share the solar spectrum. The structure consists of two sub-cells on top of each other, with the top cell absorbing the blue photons and the bottom cells absorbing the red photons. Tandem cells on silicon are interesting because they provide a pathway for more efficient commercial solar cells. Two problems of current tandem cells on silicon are: low-loss tunnel junction and efficient absorbing semiconductor for the top subcell. The first part of the thesis deals with the design of tunnel diodes. Tunnel diodes are used at the interface of the two sub-cells to enable passage or transport of carriers from one cell to another by the quantum mechanical phenomenon of tunneling. Low-loss tunnel junctions offer a low resistance and optically transparent connection between two sub cells. Here we report “all-oxide” heterojunction diodes which have the potential to behave like tunnel junction diodes. For this study we chose nitrogen doped as the p+-type material and ITO as the n+-type material, both deposited using magnetron sputtering. The primary materials challenge is deposition of degenerately doped oxide thin-films. Through careful optimization of deposition conditions highly-doped Cu2O and ITO films with a peak doping concentration of 2.6 x , and 2.0 x were obtained. Next, tunnel diodes with p+- /n+-ITO structure in various configurations were fabricated. Negative differential resistance, the characteristics feature in the I-V characteristics of a tunnel diode, was not observed in any of the devices. This could occur due to several reasons: a) the I-V characteristics of the tunnel devices may be reflecting the series resistance due to the bulk resistance of the constituent layers, b) the thermal generation current due to the bulk and interface defects may be much higher than the tunneling current, or c) insufficient doping in the p+ layer. However, we did measure very low contact resistance in the range of (4-35) mΩ across the tunnel diode, which was the ultimate goal of the project. The second part of the thesis deals with development of oxide based absorbers for silicon tandem cells. Low bandgap oxide (and sulfide) semiconductors can absorb solar radiation, and be deposited using low cost methods like PLD, making them interesting as solar absorbers. Here we report as an oxide absorber which has a low bandgap of 2.1 eV. Unfortunately solar cells made with show a very low electrical output: open circuit voltage is only 10 mV. However, the devices do show a photocurrent density of 3.87 at 1 V bias, making them interesting as a photosensor. The device performance seems to be limited by the presence of pinholes in the films. Finally we show that the can be sulphurized into another potential solar absorbing semiconductor.

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Chiang, Chia-Lin, i 江佳霖. "a-Si/a-Si silicon-based tandem solar cells". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/88093182292251398940.

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碩士
國立交通大學
光電工程學系
99
In this article, we used AMPS-1D software to simulate tandem solar cells, and also used high-density plasma chemical vapor deposition (HDPCVD) to deposit a-Si/a-Si tandem solar cells. Comparing the experiment results with the simulation results, they almost have the same trend. Thus, AMPS-1D could be used to predict the experiment results, and reduce the time to try and error. In the simulation, we successfully added tunneling recombination junction (TRJ) to simulate tandem solar cells. This article discussed the influence of four kinds of different material compositions in the a-Si/a-Si tandem solar cells, including n-a-Si/p-a-Si, n-a-Si/p-μc-Si, n-μc-Si/p-μc-Si and n-μc-Si/p-a-SiC. The results showed that n-μc-Si/p-μc-Si is the best choice for the recombination junction (RJ) of a-Si/a-Si tandem solar cells because its low resistance and low mobility gap. Also, we optimized a-Si/a-Si tandem solar cells. When i-layer thickness of top cell and bottom cell were 75nm and 450nm individually, the efficiency could reach 10.384%. In the experiment, we used N&K analyzer to analysis a-Si film, and found that the optical gap was around 1.8eV. Also, Raman spectroscopy and X-ray diffraction were used to analyze μc-Si film. After that, these films deposited a-Si/a-Si tandem solar cells. By changing the parameters of the RJ, we found that decreasing the np junction thickness could reduce the resistance, and varying the np junction doping concentration almost didn’t change the resistance. When increasing the np junction doping concentration, the electric field could enhance and the efficiency could reach higher. With varying the i-layer thickness and the mobility gap of top cell and bottom cell and using p1-a-SiC window layer, the efficiency of a-Si/a-Si tandem solar cell could reach about 8.5%. Finally, we also used AMPS-1D to optimize a-Si/μc-Si tandem solar cells and a-Si/a-SiGe tandem solar cells to predict the experiment trend. By changing i-layer thickness and the mobility gap of top cell and bottom cell, their efficiency could reach 11.198% and 11.777% individually.

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"Light Management for Silicon and Perovskite Tandem Solar Cells". Doctoral diss., 2019. http://hdl.handle.net/2286/R.I.55682.

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abstract: The emergence of perovskite and practical efficiency limit to silicon solar cells has opened door for perovskite and silicon based tandems with the possibility to achieve >30% efficiency. However, there are material and optical challenges that have to be overcome for the success of these tandems. In this work the aim is to understand and improve the light management issues in silicon and perovskite based tandems through comprehensive optical modeling and simulation of current state of the art tandems and by characterizing the optical properties of new top and bottom cell materials. Moreover, to propose practical solutions to mitigate some of the optical losses. Highest efficiency single-junction silicon and bottom silicon sub-cell in silicon based tandems employ monocrystalline silicon wafer textured with random pyramids. Therefore, the light trapping performance of random pyramids in silicon solar cells is established. An accurate three-dimensional height map of random pyramids is captured and ray-traced to record the angular distribution of light inside the wafer which shows random pyramids trap light as well as Lambertian scatterer. Second, the problem of front-surface reflectance common to all modules, planar solar cells and to silicon and perovskite based tandems is dealt. A nano-imprint lithography procedure is developed to fabricate polydimethylsiloxane (PDMS) scattering layer carrying random pyramids that effectively reduces the reflectance. Results show it increased the efficiency of planar semi-transparent perovskite solar cell by 10.6% relative. Next a detailed assessment of light-management in practical two-terminal perovskite/silicon and perovskite/perovskite tandems is performed to quantify reflectance, parasitic and light-trapping losses. For this first a methodology based on spectroscopic ellipsometry is developed to characterize new absorber materials employed in tandems. Characterized materials include wide-bandgap (CH3NH3I3, CsyFA1-yPb(BrxI1-x)3) and low-bandgap (Cs0.05FA0.5MA0.45(Pb0.5Sn0.5)I3) perovskites and wide-bandgap CdTe alloys (CdZnSeTe). Using this information rigorous optical modeling of two-terminal perovskite/silicon and perovskite/perovskite tandems with varying light management schemes is performed. Thus providing a guideline for further development.
Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2019

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Li-WenShen i 沈莉雯. "Investigation performance of silicon and silicon germanium tandem solar cells with distributed Bragg reflector". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/67953754827610871867.

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碩士
國立成功大學
光電科學與工程學系
101
In this work, the titanium dioxide (TiO2) and silicon dioxide (SiO2) were alternately deposited using electron beam evaporation system to form the distributed Bragg reflector (DBR), and the conductive metal pillars prepared by photo-etching were added into the DBR to enhance the conductivity; we use this structure as the intermediate reflector in the silicon and silicon germanium tandem solar cell. Transparent TiO2 and SiO2 could be deposited by electron beam evaporation system in O2 ambient. The 65-nm-thick TiO2 film and 103.5-nm-thick SiO2 film were alternately deposited for 2.5 pairs to form the DBR with high reflectivity of 55% at wavelength of 515 nm. By using this structure as the intermediate reflector in the tandem cell, the short-wavelength light would be reflected to the top cell to be reused. Therefore, the thickness of the active layer of the top cell could be reduced, and the current extraction efficiency would be enhanced consequently. Moreover, we designed and added the patterned conductive aluminum pillars into the insulating DBR to enhance the conductivity. With this conductive intermediate reflector, the conversion efficiency of the tandem solar cell is 1.368%.

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Wu, Yiliang. "Towards Highly Efficient Perovskite/c-Si Monolithic Tandem Solar Cells". Phd thesis, 2018. http://hdl.handle.net/1885/162745.

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Solar photovoltaic technology based on crystalline silicon (c-Si) has dramatically reduced in cost in the last several years, to the point where the cost of solar electricity now rivals that from coal power plants in many locations around the world. Increasing the power conversion efficiency is the most promising method to further reduce the cost. Since the efficiency of c-Si cells is approaching its theoretical limit, alternative approaches are required to enable step changes in efficiency. The rapid development of perovskite cells provides an opportunity to fabricate highly efficient perovskite/c-Si tandem cells, with an efficiency substantially greater than that possible with c-Si. One potential difficulty to achieve a highly efficient perovskite top cell for such a tandem device is the hysteresis behaviour usually displayed by these cells. It is necessary to understand the root causes of hysteresis in order to assess whether and to what extent the underlying mechanisms responsible will limit the efficiency or stability of the cells. We show for the first time, that the transient changes in terminal voltage and luminescent intensity do not follow the relationship that would be predicted by the generalised Planck radiation law. Using numerical simulation, we demonstrate that due to the accumulation of mobile ions at interfaces and together with significant defect related interface recombination, a resistive barrier to majority carrier flow at the interfaces between the perovskite film and the electron or hole transport layer can result in decoupling of the internal quasi-Fermi level separation and the externally measured voltage. Additional to the perovskite work, we report a specially designed homojunction c-Si solar cell architecture which provides a wide window for the perovskite top cell processing temperature of up to 400 °C, and which features passivation on both sides of the c-Si substrate using conventional, industry standard homojunction (diffused junction) technology. With a modified vacuum flash assisted perovskite deposition method, we demonstrate a 1 cm2 monolithic perovskite/c-Si tandem cell with 22.5% stabilized efficiency, which is the highest efficiency reported to date with a homojunction c-Si substrate. The unique design presented in this work opens up a new approach for achieving highly efficient monolithic perovskite/c-Si tandem devices. In the final work, we carefully investigate the monolithic tandems based on HJT (heterojunction technology) and PERT (passivated emitter rear totally diffused) structures recently published. Based on the simulation results, for both structures, we show that a significant increase in efficiency can be achieved by simply reducing the resistivity of the c-Si wafer and changing the wafer from n-type to p-type without changing any process conditions for the entire monolithic tandem. Two new structures - LERL (localized emitter rear localized diffused) and rTOPCon (reversed tunnelling oxide passivating contact) are also proposed and simulated in this work to further improve the device efficiency while tolerating up to 400 oC processing temperature, which substantially increases the process flexibility for the perovskite cell. Importantly, the rTOPCon structure is industrially feasible for large scale production.

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Chapa, Manuel Manta. "2D Optimization of Thin Perovskite/Silicon Four-Terminal Tandem Solar Cells". Master's thesis, 2018. http://hdl.handle.net/10362/56426.

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A model capable of describing the optoelectronic response of tandem photovoltaic cells is introduced, employing commercial software provided by Lumerical Solutions Inc. Specifically, a four-terminal thin perovskite/silicon architecture is studied, with special focus on the optical properties of the interlayer, and also on the ITO contact problematic – tackled by an alternative design, where all but one transparent contact are comprised of state-of-the-art transparent metallic structured grids. Furthermore, a look into how light-trapping formalisms are essential to the suc-cess of this architecture is taken. Thus, this research aims to demonstrate the means to overcome one of the main constraints in tandem cells performance, the transparent oxide’s parasitic absorption characteristics. Addi-tionally, the possibility of highly efficient, thin and flexible, solar cells is explored, being con-cluded that these can be achieved with the referred architecture after careful optimization of the design parameters. The developed optoelectronic model can predict the response of heterojunc-tion solar cells, and also of modelling perovskite solar cells – aspects which are not commonly reported in recent literature. The parasitic absorption is reduced by 30% when replacing two ITO contacts by the novel metallic grid alternatives. Simultaneously, on a hypothetical light-management scenario where 10x optical path length in the bottom layer is implemented, up to 27% efficiency is achievable by the tandem device. The attained results can be used as a guideline for forthcoming architecture improvements showing promise for the future of thin and flexible photovoltaic applications.

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Yang, Tsai-Ting, i 楊蔡廷. "Fabrication of Microcrystalline Silicon Solar Cells on Nanostructured Back Reflectorsand Micromorph Tandem Solar Cells". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/22033309162440461036.

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碩士
國立臺灣大學
電子工程學研究所
101
The characteristics of a-Si:H and μc-Si:H thin films deposited by HWCVD, including structure, optical and electrical properties, were investigated first to choose the proper deposition parameters for solar cells in this thesis. Then it was introduced to the fabrication of amorphous silicon solar cells. Besides, microcrystalline silicon solar cells were fabricated, and in order to increase the optical path length within the cell by light scattering, the hexagonal silver nanostructures as back reflectors were studied and employed. The best performance of the patterned solar cell was achieved with 25% and 39% enhancement in η and Jsc compared to the flat cell. Finally, the I-V characteristics and external quantum efficiency of amorphous and microcrystalline silicon solar cells are compared. In order to obtain higher open-circuit voltage and wider light absorption spectra, the micromorph tandem solar cell was fabricated. The open-circuit voltage of the best cell could be increased to 865 mV with wider absorption spectra comparing to the single junction a-Si:H solar cell and its efficiency was 2.26%.

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39

Duong, The. "Development of High Efficiency Four-Terminal Perovskite-Silicon Tandems". Phd thesis, 2017. http://hdl.handle.net/1885/134476.

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This thesis is concerned with the development of high efficiency four-terminal perovskite-silicon tandem solar cells with the potential to reduce the cost of solar energy. The work focuses on perovskite top cells and can be divided into three main parts: developing low parasitic absorption and efficient semi-transparent perovskite cells, doping perovskite materials with rubidium, and optimizing perovskite material’s bandgap with quadruple-cation and mixed-halide. A further section investigates the light stability of optimized bandgap perovskite cells. In a four-terminal mechanically stacked tandem, the perovskite top cell requires two transparent contacts at both the front and rear sides. Through detailed optical and electrical power loss analysis of the tandem efficiency due to non-ideal properties of the two transparent contacts, optimal contact parameters in term of sheet resistance and transparency are identified. Indium doped tin oxide by sputtering is used for both two transparent contacts and their deposition parameters are optimized separately. The semi-transparent perovskite cell using MAPbI3 has an efficiency of more than 12% with less than 12% parasitic absorption and up to 80% transparency in the long wavelength region. Using a textured foil as anti-reflection coating, an outstanding average transparency of 84% in the long wavelength is obtained. The low parasitic absorption allows an opaque version of the semi-transparent perovskite cell to operate efficiently in a filterless spectrum splitting perovskite-silicon tandem configuration. To further enhance the performance of perovskite cells, it is essential to improve the quality of perovskite films. This can be achieved with mixed-perovskite FAPbI3/MAPbBr3. However, mixed-perovskite films normally contain small a small amount of a non-perovskite phase, which is detrimental for the cell performance. Rb-doping is found to eliminate the formation of the non-perovskite phase and enhance the crystallinity of the films. Rb-doping is studied under different excess PbI2 concentrations and the optimal condition is found to be 5% Rb-doping and 15% excess PbI2 concentration. The addition of more than 10% Rb results in the formation of an unwanted Rb-rich phase due to the significant lattice mismatch between Rb and FA/MA cations. An efficiency of 18.8% is achieved for the champion cell as compared to 16% with control cells. Importantly, Rb-doping improves the light, moisture and thermal stability of perovskite cells. The optimal bandgap of the perovskite top cell in perovskite-silicon tandems is between 1.7 eV and 1.8 eV. A quadruple-cation Rb/Cs/FA/MA mixed-halide I/Br perovskite composition is explored to obtain high quality perovskite films with a bandgap of 1.73 eV. The ratio between Cs/FA/MA cations is critical to the morphology, crystal orientation and electronic properties of perovskite films. Furthermore, 5% Rb-doping enhances the crystallinity and suppresses defect migration in the films. Semi-transparent cells with efficiencies up to 16% and negligible hysteresis are achieved using this material. With excellent transparency and optimal bandgap of the semi-transparent perovskite cell, a record four-terminal mechanically stacked perovskite-silicon tandem efficiency of 26.4% is achieved.

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40

Lee, Chien-Ya, i 李建亞. "Development of Tandem Thin-Film Silicon Solar Cells by Plasma-Enhanced Chemical Vapor Deposition". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/87907529828326516057.

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碩士
國立交通大學
光電工程學系
99
In this study, the major objective is to develop silicon based tandem solar cell. There are two directions to achieve this objective: development of a-Si:H / a-Si:H tandem solar cell and deposition and characteristic of the intrinsic μc-Si:H thin film to fabricate a-Si:H / μc-Si:H tandem solar cell. Both a-Si:H and μc-Si:H were deposited by plasma-enhanced chemical vapor deposition (PECVD) system at 27.12 MHz In the part of a-Si:H / a-Si:H tandem solar cell, we varied the thickness of top cell to achieve current matching. Beside, the band-gap profiling is used in buffer grading to improve short-circuit current density (Jsc). μc-Si:H n-layer is applied in tunneling recombination junction (TRJ), it shows no reverse electric field against the built-in voltage of top and bottom cell compared with the TRJ with μc-Si:H n-layer. In the part of intrinsic μc-Si:H thin film deposition, The effect of total flow rate, power and hydrogen dilution ratio on intrinsic μc-Si:H thin film characteristic has been studied. The μc-Si:H thin films were deposited under high pressure and high power condition. The transition region from a-Si:H to μc-Si:H shows a good material characteristic both in X-ray diffraction spectroscopy (XRD) and photosensitivity.

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41

Kuan-HaoChen i 陳冠豪. "Laser-assisted n+ Microcrystalline Silicon Tunnel Junction for a-Si/a-SiGe Tandem Solar Cells". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/70479883711157994735.

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碩士
國立成功大學
微電子工程研究所碩博士班
100
The topic of this research is n+ microcrystalline silicon film deposited at low temperature based on Laser-assisted Plasma-Enhanced Chemical Vapor Deposition system (LAPECVD). Since silane shows extremely high absorption coefficient to CO2 laser at certain wavelength (10.6 um), the CO2 laser beam is applied to the chamber during deposition of silicon film. It makes amorphous silicon be converted into a microcrystalline phase. In application, this research applies the high quality n+ microcrystalline silicon film to the tunnel recombination junction of the tandem solar cell consisting of an amorphous silicon top cell and an amorphous silicon-germanium bottom cell, which expects to improve a whole cell performance by better transmission capability of both top and bottom cell due to the high carrier concentration, high carrier mobility, low resistivity and low optical gap in microcrystalline film. The tunnel junction produced by Laser-assisted Plasma-Enhanced Chemical Vapor Deposition system (LAPECVD) significantly enhances efficiency of tandem solar cell from 6.40% to 8.07%, and increases the fill factor from 0.54 to 0.59.

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42

Hsiao, Min-Wen, i 蕭閔文. "Improvement of Microcrystalline Silicon Single-Junction and Tandem Solar Cells by Optimizing N-Type Microcrystalline Silicon and Silicon Oxide as Doped and Back Reflecting Layers". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/krs8f5.

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43

"Modeling Towards Lattice-Matched Dilute Nitride GaNPAs on Silicon Multijunction Solar Cells". Doctoral diss., 2019. http://hdl.handle.net/2286/R.I.54918.

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abstract: Silicon photovoltaics is the dominant contribution to the global solar energy production. As increasing conversion efficiency has become one of the most important factors to lower the cost of photovoltaic systems, the idea of making a multijunction solar cell based on a silicon bottom cell has attracted broad interest. Here the potential of using dilute nitride GaNPAs alloys for a lattice-matched 3-terminal 2-junction Si-based tandem solar cell through multiscale modeling is investigated. To calculate the electronic band structure of dilute nitride alloys with relatively low computational cost, the sp^3 d^5 s^* s_N tight-binding model is chosen, as it has been demonstrated to obtain quantitatively correct trends for the lowest conduction band near Γ, L, and X for dilute-N GaNAs. A genetic algorithm is used to optimize the sp^3 d^5 s^* tight-binding model for pure GaP and GaAs for their optical properties. Then the optimized sp^3 d^5 s^* s_N parametrizations are obtained for GaNP and GaNAs by fitting to experimental bandgap values. After that, a virtual crystal approach gives the Hamiltonian for GaNPAs alloys. From their tight-binding Hamiltonian, the first-order optical response functions of dilute nitride GaNAs, GaNP, and GaNPAs are calculated. As the N mole fraction varies, the calculated critical optical features vary with the correct trends, and agree well with experiment. The calculated optical properties are then used as input for the solar device simulations based on Silvaco ATLAS. For device simulation, a bottom cell model is first constructed to generate performance results that agree well with a demonstrated high-efficiency Si heterojunction interdigitated back contact (IBC) solar cell reported by Kaneka. The front a-Si/c-Si interface is then replaced by a GaP/Si interface for the investigation of the sensitivity of the GaP/Si interface to interface defects in terms of degradation of the IBC cell performance, where we find that an electric field that induces strong band bending can significantly mitigate the impact of the interfacial traps. Finally, a lattice-matched 3-terminal 2-junction tandem model is built for performance simulation by stacking a dilute nitride GaNP(As) cell on the Si IBC cell connected through a GaP/Si interface. The two subcells operate quasi-independently. In this 3-terminal tandem model, traps at the GaP/Si interface still significantly impact the performance of the Si subcell, but their effects on the GaNP subcell are relatively small. Assuming the interfacial traps are well passivated, the tandem efficiency surpasses that of a single-junction Si cell, with values close to 33% based on realistic parameters.
Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2019

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44

Baerhujin, Qiaoke. "Photoluminescence Spectroscopy for Understanding Light Management in Solar Cells". Phd thesis, 2015. http://hdl.handle.net/1885/104493.

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The purpose of applying a light management structure in a solar cell is to absorb the largest possible amount of incident radiation in the active layer. Independent of the material, thickness and structure of the solar cell, the fundamental approaches for light management are: A) reducing the proportion of the light being reflected out at the front surface and B) increasing the path length of the light within the absorbing substrate. Therefore, characterizing and optimizing the light management technique is essential for further improving solar cell efficiency. In this thesis, a method based on the generalized Planck’s law of radiation is developed to extract the band-to-band absorptance from the photoluminescence spectra of semiconductor materials. Unlike the traditional way of obtaining absorptance from the reflection and transmission measurement, this method is only sensitive to absorbed photons that can generate electron-hole pairs. Therefore, the parasitic losses such as free carrier absorption and the absorption in non-active layers can be automatically eliminated. With the extracted band-to-band absorptance, the implied photo-current of the sample is accurately estimated without the need of forming a p-n junction. By comparing the band-to-band absorptance of silicon wafers with and without light trapping structure, the optical enhancement is rapidly accessed. Using this method, a wide range of light trapping structures are studied on crystalline silicon wafers to improve the photo-current generation. Self-assembled plasmonic Ag particles (AgNP) together with a dielectric based diffuse reflector (DR) are applied on the rear side of silicon wafers to provide excellent optical enhancement without sacrificing the electrical performance of the device. AgNP have proven to scatter the light at wide angles, so that total internal reflection occurs and the light can be trapped in the solar cell. Dielectric based diffuse reflectors have the advantage of high reflectivity and low absorption loss compared to metal reflectors. The combination of DR and AgNP provides light trapping performance (62% of Lambertian enhancement) which is comparable with inverted pyramids (67% of Lambertian enhancement) on a 200 mm thick silicon wafer. By applying AgNP in the back of a silicon wafer with an interdigitated back contact (IBC) structure, a maximum of 53% of fraction of the Lambertian enhancement is achieved with an optimized capping layer. For a standard IBC cell with AgNP embedded in the rear side, the short circuit current density is estimated to enhance by 18% in the spectral range from 1000 nm to 1200 nm. Texturing is still the most widely applied light management technique in the c-Si solar cell industry. The textured surface produces broad-band anti-reflection properties as well as effective light trapping to the solar cell. We extend the application of the PL technique to evaluate the optical performance of textured samples. Several structures including reactive ion etched textures (RIE), metal-assisted textures (MET) and random pyramid textures (RAN) are experimentally evaluated with the photoluminescence technique. By fabricating a silicon wafer with RIE and RAN textures on the front and rear side respectively, we demonstrate a structure with near ideal absorption in the ultraviolet and visible spectrum and a light trapping efficiency of 55% in the near infrared region of the solar spectrum. Using an analytical model with independent angular distribution parameters on both surfaces, we carry out a quantitative analysis on the impact of front reflection, rear absorption and the angular distribution on the implied current generation of these silicon samples. With the origins of the optical loss of these light management structures revealed, the effective approach for reaching maximum photo-current for high efficiency silicon solar cells is discussed. We conclude that the non-perfect angular distribution is the main limitation for approaching Lambertian light trapping in high efficiency silicon solar cells. Dielectric based diffuse reflectors have excellent optical properties and can be applied on a wide range of solar cells. A diffuse reflector prepared by Snow Globe coating is applied on a-Si:H/mc-Si:H tandem solar cell. The reflector has close to 100% reflectance over a spectral range of 500-1300 nm which indicates much lower parasitic optical losses compared to the standard textured ZnO:Al/Ag reflector. The application of DR avoids the localized surface plasmon and propagating surface plasmon resonances existing on randomly textured ZnO:Al/Ag back contacts. Both of the resonances can couple with the incident light and introduce significant amount of parasitic absorption and thereby reducing the overall cell performance. By replacing ZnO:Al/Ag with SGC reflector on tandem thin film silicon solar cells as a rear reflector, the short circuit current of the bottom solar cell is enhanced and the overall cell efficiency is improved from 10.2% to 10.4%. Organic/inorganic hybrid perovskite material has the potential for being a lowcost and high efficiency photovoltaic technology. The knowledge of absorption coefficient of such novel absorber materials is essential in understanding the extent to which perovskite solar cells may suffer from parasitic absorption. The fundamental relationship between band-to-band absorptance and photoluminescence is used to measure the absorption coefficient absorption coefficient of organic-inorganic hybrid perovskite methylammonium lead iodide (CH3NH3PbI3) films from 675 nm to 1400 nm. Unlike other methods used to extract the absorption coefficient, photoluminescence is only affected by band-to-band absorption and is capable of detecting absorption events at very low energy levels. Absorption coefficients as low as 10e-14 cm-1 are detected at room temperature for long wavelengths, which is 14 orders of magnitude lower than reported values at shorter wavelengths. The temperature dependence of absorption coefficient is calculated from the photoluminescence spectra of CH3NH3PbI3 in the temperature range 80-360K with 10K intervals. Based on the temperature dependent absorption coefficient, a polynomial parameterization describing the product of the radiative recombination coefficient and square of the intrinsic carrier density is also presented. This thesis focuses on understanding and improving the light management of solar cells. The method of extracting band-to-band absorptance from photoluminescence spectra is used to compare a wide range of light trapping structures on silicon wafers and to extract the absorption coefficient of perovskite film at very low energy levels.

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45

Mukherjee, Rudra. "Band-matched transport layers and intrinsically stable perovskite solar cells for application to perovskite Si tandem cells". Thesis, 2020. https://etd.iisc.ac.in/handle/2005/5512.

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Hybrid perovskite/silicon tandem solar cells offer low-cost alternatives to the commercially established silicon solar cells. In this thesis, we present the material and device optimizations of the subcells that can be used to fabricate tandem cells: Methylammonium Lead Halide (MAPbI3) based perovskite solar cells and Silicon/metal oxide type-II heterojunction based solar cells. Specifically, we focus on (a) improving the Voc of (MAPbI3) solar cells using band-matched polymer hole transporting layers (HTL), (b) improving the intrinsic stability of MAPbI3 by introducing Acetamidinium (AA) cation in the matrix, (c) studying the effect of Magnesium and Bromine substitution in MAPbI3, and (d) developing a Silicon/Cu2O type-II heterojunction solar cell that can act as a bottom cell in the proposed perovskite/silicon tandem solar cell. a) The fermi-splitting (in the absorber) and consequently the Voc of a thin film heterojunction cell depends on the fermi-level of the adjacent transport layers. The most widely used HTL: Spiro-OMeTAD has a HOMO of -5.0 eV, a 0.5 eV valance band maxima (VBM) offset with MAPbI3. In this part, we examine whether a p-type semiconducting polymer: ‘Poly-4-(5-(9,9-dihexyl-7-methyl-9H-fluoren-2-yl)thiophen-2-yl)-5,6-difluoro-7-(5-methylthiophen-2-yl)benzo[c][1,2,5]thiadiazole’ (PF-DTDFBT) having a HOMO level of -5.6 eV: exactly matched to the VBM of MAPbI3 leads to the enhancement of the Voc of the cell. The increased fermi-splitting directly contributed to the improvement of Voc from 1.04 V in standard Spiro-OMeTAD HTL devices to 1.11 V in PF-DTDFBT interlayer devices. In addition, the polymer being hydrophobic leads to an increase in device stability by reducing the seepage of moisture into the active perovskite layer slowing down its degradation. b) One of the major obstacles in the commercialization of perovskites is its instability towards moisture, optical and thermal stimulus. The MAPbI3 structure consists of the organic methyl-ammonium (MA+) cation held in the PbI64- octahedral cage by 3 hydrogen bonds, weakened by the continuous tumbling motion of the C-N spine (in MA+). We report a cation : Acetamidinium, having (i) 4 h-bonds and (ii) restricted C-N bond rotation, that binds more strongly with the PbI64- cage as compared to MA+. Acetamidinium substitution leads to improvement in device performance and stability, which retained 70% of their initial PCE in 480 hours, while the standard cells degrade to ~43 % of their initial PCE in the same time frame. c) The state-of-the-art perovskite devices use the recipe involving weak co-ordination bond between DMSO-PbI2 (solvent-solute binding) broken by an in-situ antisolvent drip (Toluene or Chlorobenzene) to control the nucleation density and grain growth rate. Although for small device areas (~ 1 cm2) this method provides dense compact films with 200-250 nm grain sizes, this method is not suited for depositing films on large area, required for making efficient solar panels. We present the controlled addition of MgCl2/MgI2 in perovskite in the precursor solution that helps in forming films comparable in quality (compactness, grain sizes and carrier lifetime) with the films deposited by anti-solvent drip method. This deposition method neither requires DMSO nor anti-solvent drip making it more commercially attractive. 10% MgCl2/MgI2 addition in MAPbI3 leads to a ~ 80 μs/120 μs increase in carrier lifetime as measured by resonance assisted microwave photoconductance supporting a 150 mV rise in Voc of the devices. d) A silicon/metal oxide heterojunction solar cell is expected to have a lower thermal budget and a higher Jsc as compared to the more popular silicon homojunction cell where a considerable number of incoming photons are lost to the free carrier absorption in the highly doped p++ emitter region. We report the optimization of a type-II n-silicon/Cu2O heterojunction based solar cell. The Si/Cu2O interface is passivated by a 1.3 nm ultra-thin silicon dioxide layer. The passivated devices showed a 200 mV increase in Voc over the unpassivated devices. Further in-situ p-type doping of Cu2O was done by incorporating nitrogen into the Cu2O crystal. This served two purposes : the Voc and FF increased due to enhanced built-in voltage and film conductivity respectively, and the hole fermi-level is now defined by the doped Cu2O layer, providing the relaxation to use lower work function transparent contacts (which otherwise would have decreased the Voc of the cell). The best devices : doped-Cu2O/Si cells with transparent ITO top contact exhibited 5.23% PCE.
Department of Science and Technology, GoI.; Solar Energy Research Institute for India and the UnitedStates (SERIIUS) ; Visvesvaraya PhD Scheme for Electronics & IT program by MeitY, GoI

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46

Chien, Chih-Chun, i 簡誌君. "Study of N-type Microcrystalline Silicon Oxide as Intermediate Reflecting Layer for a-Si:H/a-Si1-XGeX:H Tandem Solar Cells". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/61770225291787579044.

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碩士
國立交通大學
光電工程研究所
102
In this thesis, the thin-film tandem solar cells were prepared by a 27.12 MHz radio-frequency plasma-enhanced chemical vapor deposition (PECVD) system. The bandgap of the amorphous silicon germanium (a-Si1-XGeX:H) can be adjusted by Ge-incorporation. In addition, the a-Si1-XGeX:H material is suitable for the middle or the bottom absorber due to its higher optical absorption in long wavelength region. The a-Si:H / a-Si1-XGeX:H tandem cell was employed due to better utilization of solar spectrum. In order to improve the performance of a-Si:H / a-Si1-XGeX:H tandem solar cell, we introduced a n-type microcrystalline silicon oxide (μc-SiOX:H(n)) intermediate reflecting layer (IRL) between the top and bottom cells to reflect the light back to a-Si:H top cell and reduce the optical loss in a-Si1-XGeX:H bottom cell. Thus, the requirements of μc-SiOX:H(n) as IRL were larger bandgap, lower refractive index and acceptable conductivity. The oxygen content and the conductivity of μc-SiOX:H(n) were the critical factors to affect cell performance. The IRL was optimized to be wider bandgap and acceptable conductivity. In our results, the optimized bandgap of μc-SiOX:H(n) was 2.09 eV and the acceptable conductivity was approximately 10-1 S/cm. In addition, tunneling recombination junction (TRJ) layer was also employed in a-Si:H / a-Si1-XGeX:H tandem cells. As a result, we used μc-SiOX:H(n) layers as IRL to obtain optimum cell efficiencies. Finally, the open circuit voltage (VOC), short circuit current density (JSC), fill factor (F.F.) and conversion efficiency (η) of a-Si:H / a- Si1-XGeX:H tandem cell with the optimized μc-SiOX:H(n) IRL were improved to 1.6 V, 8.23 mA/cm2, 70.3% and 9.26%, respectively.

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47

Chen, Chien-Wei, i 陳建瑋. "Optical simulation of silicon thin-film tandem solar cells and optimization of surface texturing design parameters for improving energy conversion efficiency". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/80953914007056087000.

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碩士
國立臺灣科技大學
光電工程研究所
101
In this work, we used commercial optical simulation software FRED to simulate surface-textured solar cells and to study the optical properties under various conditions. First we studied the scattering efficiency in terms of haze and equivalent optical path length factor as a function of scatter size for four incident light wavelengths: 550nm, 700nm, 900nm and 1200nm.Thus the ideal range in scatter size for silicon thin-film solar cells was obtained. After that, we studied and found a linear relationship between the surface coverage percentage of scatters and the equivalent optical path length factor. Then we carried out the simulations of single-junction and tandem cells respectively and obtained the absorptance of the active layers versus incident light wavelength. The materials used for the single junction and tandem cells were a-Si: H (hydrogenated amorphous silicon) and μc-Si: H (hydrogenated microcrystalline silicon), respectively. Consequently the external quantum efficiency versus incident wavelength, the short-circuit current density and the energy conversion efficiency can be obtained under standard 1-sun AM1.5G solar spectrum. In the single-junction cell simulation, the ideal scatter size chosen was 0.05μm (+ / -5%), and the results showed that the scattering layer improved both the short-circuit current density and the conversion efficiency by about 12%. In the tandem cell simulation, compared to the one without scatters, the two tandem cells with different scatter sizes of III 0.055μm (+ / -5%) and 0.075μm (+ / -5%) helped increase the short-circuit current density by 25.7% and 22.0%, respectively, and both have reached 15% in conversion efficiency.

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48

Tsao, You-Yu, i 曹佑羽. "Development of p-type and n-type Microcrystalline Silicon Oxide as Tunnel-Recombination Junction and Intermediate Reflecting Layer in a-Si:H/a-Si1-xGex:H Tandem Solar Cells". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/ztkacm.

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碩士
國立交通大學
光電工程研究所
103
The a-Si:H/a-Si1-xGex:H tandem cell is an important building block for high-efficiency triple-junction solar cells. To improve the stability of a-Si:H/a-Si1-xGex:H tandem cells against light exposure, the thickness of the a-Si:H top cell needed to be reduced because high-energy photons were mostly absorbed by a-Si:H absorber. The reduction of thickness can be realized by employing intermediate reflecting layer (IRL) between a-Si:H top and a-Si1-xGex:H bottom cell. The IRL typically exhibited lower refractive index than a-Si:H and a-Si1-xGex:H that established a difference in refractive index, reflecting unabsorbed photons back into the a-Si:H top cell. This increased the photocurrent of a-Si:H top cell and thus entailed the possibility to reduce the thickness of a-Si:H. The microcrystalline silicon oxide (μc-SiOx:H) having tunable and reduced refractive index with the incorporation of oxygen is suitable for the application as IRL. However, there is a trade-off between its optical and electrical properties with the incorporation of oxygen. In this thesis, we employed a 27.12 MHz radio-frequency plasma-enhanced chemical vapor deposition (PECVD) system for the preparation of thin-film silicon materials. We found that oxygen incorporation was a key factor to influence the characteristics of μc-SiOx:H(n) IRL. As the oxygen content was increased from 0 at.% to 23 at.%, the E04 increased from 1.89 to 2.20 eV, refractive index decreased from 3.80 to 2.85, and the dark conductivity decreased from 1.41x101 to 6.59x10-1 S/cm. We also found that the employed 23 at.% oxygen content of μc-SiOx:H(n) IRL could reduce the thickness of a-Si:H absorber from 160 to 140 nm leading to decreased Staebler-Wronski effect. Furthermore, the VOC, JSC, FF, and efficiency of a-Si:H/a-Si1-xGex:H tandem cell with the optimized μc-SiOx:H(n) IRL were improved to 1.60 V, 8.32 mA/cm2, 67.1% and 8.82%, respectively.

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49

葉雲源. "A Study of Silicon Tandem Solar Cell". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/03955949104457967228.

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碩士
建國科技大學
電機工程系暨研究所
101
The hydrogenated amorphous Silicon(a-Si:H) and Microcrystalline Silicon thin film solar cell are prepared on ITO glass substrate by electron cyclotron resonance chemical vapor deposition(ECR CVD) system. The optoelectronic characteristics of uc-Si:H deposited by different conditions were analyzed for tandem solar cell. Energy gap of the intrinsic uc-Si:H layer, deposited with SiH4 and H2(the dilution SiH4/SiH4+H2 is 10%) at substrate temperature is 250 ℃ and microwave power is 500 W, is 1.18 eV. Measure the microcrystalline silicon solar cell efficiency of the p-i-n structure by the AM1.5 standard light source, the i-layer on solar cell oper circuit voltage(Voc), short-circuit current(Jsc), fill factor(FF) and energy conversion efficiency(η) have been investigated. The optimized uc-Si:H thin film solar cell with i-layer thickness 1600 nm was found to have Voc is 0.32 V, Jsc is 5.12 mA/cm2, FF(%) is 42.03, η is0.69 %. After carrying on Tandem, Tandem Solar Cell have Voc is 0.96 V, Jsc is 13.9 mA/cm2, FF(%) is 64.82, η is 7.41 %.

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50

Liu, Wei-Lin, i 劉威麟. "Modeling of Amorphous Silicon Tandem Solar Cell". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/84535374286527263749.

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碩士
國立交通大學
光電系統研究所
99
Due to the depletion of energy resources, alternative energy development is the trend of the future. There are many alternative energy sources, and the solar power is a clean, environmentally friendly, renewable and inexhaustible one among them. Among several types of solar cells that are currently with high attention, we chose the amorphous silicon thin-film solar cells for the subject. Thin-film solar cells can be produced on the substrates which could use inexpensive glass, plastics, ceramics, graphite, or metal, and the film only needs a few μm to produce photo-generated voltages. So under the same light-receiving area, thin-film solar cell can significantly use less amount of raw materials than the conventional silicon solar cell. One of the important characteristics of thin film solar cells is flexibility. Its flexible properties can be applied to a wide variety of surfaces even combined with the building and window. Amorphous silicon thin-film solar cell does not surpass its crystalline counterpart for high efficiency. But due to severaladvantages such as mature manufacturing process, flexibility, and combined with the building materials, the amorphous silicon solar cell research is still very popular. This research is focused on features which are different from other solar cells. One is the band tail structure of amorphous silicon materials, and the other is surface roughness. By studying the band tail physical model, we can devise the band tail absorption by tuning its parameters. And another topic is the surface roughness. We create two different surface roughness of the structure. First we use haze formula to simulate the flat structure with haze by ideal situation. On the other hand, we established the real textured surface for simulating in order to achieve the real situation. Finally, we combine the surface roughness and band tail in our simulation structure, and fitting the simulation results to the experimental data to enhance the simulation accuracy. Combination of these two features on a commercially available software is very important to expand our research for greater use. The accuracy of the simulation verified by the fitting process can ensure the validity of our band tail model and texture interface. We hope this application can be useful for design of the next generation thin film solar cell.

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