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1
Shih, Jeanne-Louise. "Zinc oxide-silicon heterojunction solar cells by sputtering". Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112583.
Testo completoAbstract (sommario):
Heterojunctions of n-ZnO/p-Si solar cells were fabricated by RF sputtering ZnO:Al onto boron-doped (100) silicon (Si) substrates. Zinc Oxide (ZnO) films were also deposited onto soda lime glass for electrical measurements. Sheet resistance measurements were performed with a four-point-probe on the glass samples. Values for samples evacuated for 14 hours prior to deposition increased from 7.9 to 10.17 and 11.5 O/□ for 40 W, 120 and 160 W in RF power respectively. In contrast, those evacuated for 2 hours started with a higher value of 22.5 O/□, and decreased down to 7.6 and 5.8 O/□. Vacuum annealing was performed for both the glass and the Si samples. Current-voltage measurements were performed on the ZnO/Si junctions in the dark and under illumination. Parameters such as open-circuit voltage, Voc; short-circuit current, Isc; fill factor, FF; and efficiency, eta were determined. A maximum efficiency of 0.25% among all samples was produced, with an I sc of 2.16 mA, Voc of 0.31V and a FF of 0.37. This was a sample fabricated at an RF power of 80 W. Efficiency was found to decline with vacuum annealing. Furthermore, interfacial state density calculated based on capacitance-voltage measurements showed an increase in the value with vacuum annealing. The results found suggest that the interface states may be due to an interdiffusion of atoms, possibly those of Zn into the Si surface. The Electron Beam Induced Current (EBIC) method was used to determine diffusion length to be at a value ∼40--80 mum and therefore a minority carrier lifetime calculated of 3 musec. It was also used to determine the surface recombination velocity (SRV) of the fractured surface of the Si bulk from the fabricated solar cells. An SRV of ∼500 cm/sec was determined from the fractured Si surface, at a point located at 30 and 20 mum away from the junction interface.
2
Richards, Bryce Sydney Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Novel uses of titanium dioxide for silicon solar cells". Awarded by:University of New South Wales. School of Electrical Engineering and Telecommunications, 2002. http://handle.unsw.edu.au/1959.4/20476.
Testo completoAbstract (sommario):
Titanium dioxide (TiO2) thin films have a long history in silicon photovoltaics (PV) as antireflection (AR) coatings due to their excellent optical properties and low deposition cost. This work explores several novel areas where TiO2 thin films could be use to enhance silicon (Si) solar cell performance while reducing device fabrication costs. Amorphous, anatase and rutile TiO2 thin films are deposited using ultrasonic spraydeposition (USD) and chemical vapour deposition (CVD) systems, both designed and constructed by the author. Initial experiments confirmed that no degradation in the bulk minority carrier lifetime (????bulk) occurred during high-temperature processing, although the stability of the USD-deposited TiO2 films was dependent on the furnace ambient. A major disadvantage of TiO2 AR coatings is that they afford little surface passivation. In this work, a novel method of achieving excellent surface passivation on TiO2-coated silicon wafers is presented. This involved growing a 6 nm-thick SiO2 layer at the TiO2:Si interface by oxidising the wafer after TiO2 film deposition. The increase in surface passivation afforded by the interfacial SiO2 layer results in a decrease in the emitter dark saturation current density (J0e) by nearly two orders of magnitude to 4.7 ??? 7.7 ??~ 10???14 A/cm2. This demonstrates the compatibility of the TiO2/SiO2 stack with high-efficiency solar cells designs. By varying the film deposition and annealing conditions, TiO2 refractive indices in the range of 1.726 ??? 2.633 (at ???? = 600 nm) could be achieved. Subsequently, a double-layer antireflection (DLAR) coating was designed comprised of low and high TiO2 refractive index material. The best experimental weighted average reflectance (Rw) achieved was 6.5% on a planar silicon wafer in air. TiO2 DLAR coatings are ideally suited to multicrystalline silicon (mc-Si) wafers, which do not respond well to chemical texturing. Modelling performed for a glass and ethyl vinyl acetate (EVA) encapsulated buried-contact solar cell indicated that a TiO2 DLAR coating afforded a 7% increase in the short circuit current density, when compared to a standard, commercially-deposited TiO2 single-layer AR coating. Finally, it is demonstrated that chemical reactions with phosphorus prevent TiO2 from acting as a successful phosphorus diffusion barrier or dopant source. The applicability of TiO2 thin films to various silicon solar cell structures is discussed.
3
Narasimha, Shreesh. "Understanding and application of screen-printed metallization, aluminum back surface fields, and dielectric surface passivation for high-efficiency silicon solar cells". Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/16453.
Testo completo
4
Fisher, Kate School of Photovoltaic & Renewable Energy Engineering UNSW. "The pitfalls of pit contacts: electroless metallization for c-Si solar cells". Awarded by:University of New South Wales. School of Photovoltaic and Renewable Energy Engineering, 2007. http://handle.unsw.edu.au/1959.4/29568.
Testo completoAbstract (sommario):
This thesis focuses on improving the adhesion of electroless metal layers plated to pit contacts in interdigitated, backside buried contact (IBBC) solar cells. In an electrolessly plated, pit contact IBBC cell, the contact grooves are replaced with lines of pits which are interconnected by the plated metal. It is shown, however, that electroless metal layers, plated by the standard IBBC plating sequence, are not adherent on pit contact IBBC solar cells. The cause of this adhesion problem is investigated by examining the adhesive properties of each of the metal layers in the electroless metallization sequence on planar test structures. This investigation reveals that Pd activation of heavily P diffused Si impedes Ni silicide growth and that, in the absence of a silicide at the Ni/Si interface, an electrolessly plated Cu layer will cause the underlying Ni layer to peel away from the substrate. It is also found that the Ni silicidation process itself intermittently causes the unreacted Ni to spontaneously peel away from the substrate. An electroless metallization sequence that results in thick, adhesive Cu deposits on planar < 100> surfaces is developed in this thesis. It is shown that this process leads to the formation of a Ni silicide on both n- and p- type, heavily diffused surfaces. Fully plated, pit contact IBBC solar cells were not able to be fabricated during the course of this work but it is reasonable to expect that the modified plating sequence developed in this work will result in the metal layers being adhesive on these cells.
5
Krygowski, Thomas Wendell. "A novel simultaneous diffusion technology for low-cost, high-efficiency silicon solar cells". Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/22973.
Testo completo
6
Weber, J??rgen Wolfgang Photovoltaic & Renewable Engergy Engineering UNSW. "Design, construction and testing of a high-vacuum anneal chamber for in-situ crystallisation of silicon thin-film solar cells". Awarded by:University of New South Wales. Photovoltaic and Renewable Engergy Engineering, 2006. http://handle.unsw.edu.au/1959.4/24847.
Testo completoAbstract (sommario):
Thin-film solar cells on glass substrates are likely to have a bright future due to the potentially low costs and the short energy payback times. Polycrystalline silicon (poly-Si, grain size > 1 pm) has the advantage of being non-toxic, abundant, and long-term stable. Glass as a substrate, however, limits the processing temperatures to ~600??C for longer process steps. Films with large grain size can be achieved by solid phase crystallisation (SPC), and especially by solid phase epitaxy (SPE) on seed layers, using amorphous silicon deposited at low temperatures as a precursor film. With SPC and SPE, the amorphous silicon film is typically crystallised at ~600??C over hours. During this anneal at atmospheric pressure -depending on the properties of the amorphous silicon film- ambient gas can percolate the film and can negatively affect the crystallisation. In this work, a high-vacuum anneal chamber was designed and built to allow the in-situ crystallisation of amorphous silicon films deposited on glass in a PECVD cluster tool. An important aspect of the design was the comfortable and safe operation of the vacuum anneal chamber to enable unattended operation. This was realised by means of a state-of-the-art, programmable temperature controller and a control circuit design that incorporates various safety interlocks. The chamber interior was optimised such that a temperature uniformity of 2-3K across the sample area was achieved. The chamber was calibrated and tested, and SPC and SPE samples were successfully crystallised. In initial SPC crystallisation experiments with solar cell structures, after post-deposition treatments, a 1 -sun open-circuit voltage of 465 mV was obtained, similar to furnace-annealed samples. In initial experiments with SPE solar cell structures, difficulties regarding the characterisation of the unmetallised solar cells with the quasi-steady-state open-circuit voltage method (QSSVOC) were encountered after post-deposition hydrogen treatment. A possible explanation for these difficulties is the contact formation with the metal probes. Furthermore, limiting factors of the QSSVOC method for the characterisation of unmetallised cells with high contact resistance values were investigated and, additionally, the accuracyof the QSSVOC setup was improved in the low light intensity range.
7
Sheng, Xing Ph D. Massachusetts Institute of Technology. "Thin-film silicon solar cells : photonic design, process and fundamentals". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/105936.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2012.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.
Includes bibliographical references (pages 153-159).
The photovoltaic technology has been attracting widespread attention because of its effective energy harvest by directly converting solar energy into electricity. Thin-film silicon solar cells are believed to be a promising candidate for further scaled-up production and cost reduction while maintaining the advantages of bulk silicon. The efficiency of thin-film Si solar cells critically depends on optical absorption in the silicon layer since silicon has low absorption coefficient in the red and near-infrared (IR) wavelength ranges due to its indirect bandgap nature. This thesis aims at understanding, designing, and fabricating novel photonic structures for efficiency enhancement in thin-film Si solar cells. We have explored a previously reported a photonic crystal (PC) based structure to improve light absorption in thin-film Si solar cells. The PC structure combines a dielectric grating layer and a distributed Bragg reflector (DBR) for effcient light scattering and reflection, increasing light path length in the thin-film cell. We have understood the operation principles for this design by using photonic band theories and electromagnetic wave simulations. we discover that this DBR with gratings exhibit unusual light trapping in a way different from metal reflectors and photonic crystals. The light trapping effects for the DBR with and without reflector are numerically investigated. The self-assembled anodic aluminum oxide (AAO) technique is introduced to non- lithographically fabricate the grating structure. We adjust the AAO structural parameters by using different anodization voltages, times and electrolytes. Two-step anodization is employed to obtain nearly hexagonal AAO pattern. The interpore periods of the fabricated AAO are calculated by fast Fourier transform (FFT) analysis. We have also demonstrated the fabrication of ordered patterns made of other materials like amorphous Si (a-Si) and silver by using the AAO membrane as a deposition mask. Numerical simulations predict that the fabricated AAO pattern exhibits light trapping performance comparable to the perfectly periodic grating layer. We have implemented the light trapping concepts combining the self-assembled AAO layer and the DBR in the backside of crystalline Si wafers. Photoconductivity measurements suggest that the light absorption is improved in the near-IR spectral range near the band edge of Si. Furthermore, different types of thin-film Si solar cells, including a-Si, mi- crocrystalline Si ([mu]-Si) and micromorph Si solar cells, are investigated. For demonstration, the designed structure is integrated into a 1:5 [mu]m thick [mu]c-Si solar cell. We use numerical simulations to obtain the optimal structure parameters for the grating and the DBR, and then we fabricate the optimized structures using the AAO membrane as a template. The prototype devices integrating our proposed backside structure yield a 21% improvement in efficiency. This is further verified by quantum efficiency measurements, which clearly indicate stronger light absorption in the red and near-IR spectral ranges. Lastly, we have explored the fundamental light trapping limits for thin-film Si solar cells in the wave optics regime. We develop a deterministic method to optimize periodic textures for light trapping. Deep and high-index-contrast textures exhibit strong anisotropic scattering that is outside the regime of validity of the Lambertian models commonly used to describe texture-induced absorption enhancement for normal incidence. In the weak ab- sorption regime, our optimized surface texture in two dimensions (2D) enhances absorption by a factor of 2.7[pi]n, considerably larger than the classical [pi]n Lambertian result and exceeding by almost 50% a recent generalization of Lambertian model for periodic structures in finite spectral range. Since the [pi]n Lambertian limit still applies for isotropic incident light, our optimization methodology can be thought of optimizing the angle/enhancement tradeoff for periodic textures. Based on a modified Shockley-Queisser theory, we conclude that it is possible to achieve more than 20% efficiency in a 1:5 [mu]m thick crystalline Si cell if advanced light trapping schemes can be realized.
by Xing Sheng.
Ph. D.
8
Jain, Nikhil. "Design of III-V Multijunction Solar Cells on Silicon Substrate". Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/33048.
Testo completoAbstract (sommario):
With looming energy crisis across the globe, achieving high efficiency and low cost solar cells have long been the key objective for photovoltaic researchers. III-V compound semiconductor based multijunction solar cells have been the dominant choice for space power due to their superior performance compared to any other existing solar cell technologies. In spite of unmatched performance of III-V solar cells, Si cells have dominated the terrestrial market due to their lower cost. Most of the current III-V solar cells are grown on Ge or GaAs substrates, which are not only smaller in diameter, but are also more expensive than Si substrate. Direct integration of high efficiency III-V solar cells on larger diameter, cheaper and readily available Si substrate is highly desirable for increased density, low-cost and lightweight photovoltaics. However, the polar-on-nonpolar epitaxy, the thermal mismatch and the 4% lattice mismatch makes the direct growth of GaAs on Si challenging, rendering the metamorphic cell sensitive to dislocations.
The focus of this work is to investigate and correlate the impact of threading dislocation density on the performance of lattice-mismatched single-junction (1J) GaAs and dual-junction (2J) InGaP/GaAs solar cells on Si substrate. Utilizing our calibrated dislocation-assisted modeling process, we present the design methodology to optimize the structure of 2J InGaP/GaAs solar cell on Si substrate. Our modeling results suggest an optimistic future for integrating III-V solar cell technology on Si substrate and will be useful for future design and prediction of metamorphic III-V solar cell performance on Si substrate.Master of Science
9
Sana, Peyman. "Design, fabrication and analysis of high efficiency multicrystalline silicon solar cells". Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/15039.
Testo completo
10
Sun, Yechuan, e 孙也川. "Improvement of polymer solar cells through device design". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B47849940.
Testo completoAbstract (sommario):
In this thesis, fabrication of polymer solar cells through different device designs is presented and the resulted solar cell performance is discussed. Poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are chosen as the photoactive layer materials as this material combination has been widely used and well investigated. The known properties of P3HT and PCBM make systematical studies and modeling for the effect of device designs on the performance of polymer solar cells possible although this is beyond the scope of this thesis.
First, ITO electrodes were fabricated by sputtering and used as the transparent electrode for polymer solar cells. Properties of ITO film fabricated by different sputtering conditions were compared. Radio frequency (RF) sputtered ITO was found to exhibit the best transparency overall. This condition was further applied to the fabrication of ITO electrode for polymer solar cells with light trapping structures. Low temperature processed silicon oxide (SiOx) / titanium oxide (TiOx) periodic structures were fabricated by sol-gel method. Optical transmittance of the bottom electrode was altered by the presence of the reflective coating and thus the absorption in the photoactive layer was affected. By varying the number of layer pairs and thickness of each layer in the reflective coating, improvement of polymer solar cell performance was found by inserting reflective coating for optimized conditions. Finally, semi-transparent polymer solar cells with inverted structure were demonstrated using conductive polymer as the anode. The process in device preparation was vacuum-free and thus could be potentially useful in large-scale roll-to-roll fabrication.published_or_final_version
Physics
Master
Master of Philosophy
11
Wilkins, Matthew M. "Design of Multi-junction Solar Cells on Silicon Substrates Using a Porous Silicon Compliant Membrane". Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24096.
Testo completoAbstract (sommario):
A novel approach to the design of multi-junction solar cells on silicon substrates for 1-sun applications is described. Models for device simulation including porous silicon layers are presented. A silicon bottom subcell is formed by diffusion of dopants into a silicon wafer. The top of the wafer is porosified to create a compliant layer, and a III-V buffer layer is then grown epitaxially, followed by middle and top subcells. Due to the resistivity of the porous material, these designs are best suited to high efficiency 1-sun applications. Numerical simulations of a multi-junction solar cell incorporating a porous silicon compliant membrane indicate an efficiency of 30.7% under AM1.5G, 1-sun for low threading dislocation densities (TDD), decreasing to 23.7% for a TDD of 10^7 cm^-2.
12
Elani, U. "The design, fabrication and assessment of interdigitated back contact silicon solar cells". Thesis, Cardiff University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354744.
Testo completo
13
Zhou, Di. "Conception and realization of solar cells based on silicon nanostructures". Thesis, Lille 1, 2013. http://www.theses.fr/2013LIL10160/document.
Testo completoAbstract (sommario):
Dans les cellules solaires planaires silicium, le matériau doit être assez épais pour que l’absorption des photons soit efficace, et dans le même temps, l’accroissement de l’épaisseur augmente les chances de recombinaison des porteurs. Afin d’avoir à la fois absorption et couche mince, des structures radiales (nanopiliers ou nanocones) peuvent être utilisées, qui ont des diamètres inférieurs à la longueur de diffusion des porteurs minoritaires, ce qui garantit une bonne collecte des porteurs. Ce travail présente la réalisation et la caractérisation de cellules solaires silicium bas coût, basées sur des nanostructures (piliers ou cônes). Pour la nanostructuration, l’usage d’un masqueur électronique est évité grâce à l’utilisation de microbilles de silice, déposées par technique Langmuir-Blodget et servant de masque à la gravure sèche des nanostructures. L’électrode face avant est en ZnO, obtenue par technique sol-gel. Avant la fabrication, une simulation des propriétés optiques des nanostructures en fonction de leur forme (densité, hauteur, diamètre,) a été réalisée à l’aide de calculs FDTD (Finite Difference Time Domain). La synthèse des films ZnO par sol gel a été optimisée (concentration des dopants, recuit thermique, hydrogénation, …) afin d’avoir la meilleure transparence optique et la plus faible résistivité. Finalement, des cellules solaires n+- i - p ont été réalisées, assemblant nanostructures et couche ZnO. Des étapes supplémentaires de passivation des défauts de surface et d’interfaces associés aux nanostructures ont été finalement menéesFor planar p-n junction solar cell, the material must be thick enough to have enough absorption, whereas increasing the thickness leads to the increase of recombination of carriers. In order to decouple the requirement of light absorption and carrier collection, nanopillars (or nanocones) radial p-n junction are introduced. Nanopillars (or nanocones) have greater absorption and radial geometry offers minimal recombination if the diameter of nanopillars ( or nanocones ) is smaller than the minority carrier diffusion length. This work presents the realization and characterization of low-cost Si nanostructures (nanopillars and nanocones) solar cell with sol-gel derived ZnO transparent electrodes. In order to decrease the fabrication price, silica balls and Lamguir-Blodgett techniques are used as the substitutes of photoresist and electrical beam lithography, respectively. Besides, ZnO thin film transparent electrodes are synthesized by low-cost sol-gel methods For pursuiting high efficiency, first of all, we have tested the absorption of nanopillars and nanocones by varying their periods, diameters, lengths and sidewalls. Second, we have optimized the electrical properties of ZnO thin film by changing the synthesis parameters, such as doping concentration, baking temperature, anneal temperature and hydrogen treatment. In the end, solar cells were fabricated based on optimized Si nanostructures and optimized ZnO thin films. Due to their bad electrical properties associated with surface defects, surface passivation methods were performed to reduce the defects concentration in p-i-n junction and improve the efficiency of solar cells
14
Rosenberg, Glenn Alan 1960. "Monolithic series connected solar cell array". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276950.
Testo completoAbstract (sommario):
Single crystal silicon solar cells for use under high concentration sunlight presently exhibit the highest conversion efficiencies. The following paper represents further work done to improve the efficiency of crystalline silicon solar cells through improved design. Design features and processing to address the loss mechanisms encountered in silicon solar cells are discussed. An improved solar cell structure has resulted from this work along with a practical processing sequence. Experiments were performed to show the practicality of pattern formation on the walls of the V-groove structures using conventional photolithography and masking techniques. Also, new beam processing techniques are discussed to improve processing.
15
Zhang, Di, e 张笛. "Transparent electrode design and interface engineering for high performance organic solar cells". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/202360.
Testo completoAbstract (sommario):
With the growing needs for energy, photovoltaic solar cells have attracted increasing research interests owing to its potentially renewable, feasible and efficient applications. Compared to its inorganic counterparts, organic solar cell (OSC) is highly desirable due to the low-cost processing, light weight, and the capability of flexible applications. While rapid progress has been made with the conversion efficiency approaching 10%, challenges towards high performance OSCs remain, including further improving device efficiency, fully realizing flexible applications, achieving more feasible large-area solution process and extending the stability of organic device.
Having understood the key technical issues of designing high performance OSCs, we focus our work on (1) introducing flexible graphene transparent electrodes into OSCs as effective anode and cathode; (2) interface engineering of metal oxide carrier transport layers (CTLs) in OSCs through incorporating plasmonic metal nanomaterials ;(3)proposing novel film formation approach for solution-processed CTLs in OSCs in order to improve the film quality and thus device performance.
The detailed work is listed below:
1. Design of transparent graphene electrodes for flexible OSCs
Flexible graphene films are introduced into OSCs as transparent electrodes, which complement the flexibility of organic materials. We demonstrate graphene can function effectively as both the anode and cathode in OSCs:
a) Graphene anode: we propose an interface modification for graphene to function as anode as an alternative to using aconventional polymer CTL. Using the proposed interfacial modification, graphene OSCs show enhanced performance. Further analysis shows that our approach provides favorable energy alignment and improved interfacial contact.
b) Graphene cathode: efficient OSCs using graphene cathode are demonstrated, using a new composite CTL of aluminum-titanium oxide (Al-TiO2).We show that the role of Al is two-fold: improving the wettability as well as reducing the work function of graphene. To facilitate electron extraction, self-assembledTiO2is employed on the Al-covered graphene, which exhibits uniform morphology.
2. Incorporation of plasmonic nanomaterialsinto the metal oxide CTLinOSCs
By incorporating metallic nanoparticles (NPs) into the TiO2CTLin OSCs, we demonstrate the interesting plasmonic-electrical effect which leads to optically induced charge extraction enhancement. While OSCs using TiO2CTL can only operate by ultraviolet (UV)activation, NP-incorporated TiO2enables OSCs to perform efficiently at a plasmonic wavelength far longer than the UV light. In addition, the effciency of OSCs incorporated with NPs is notably enhanced. We attribute the improvement to the charge injection of plasmonically excited electrons from NPs into TiO2.
3. Formation of uniform TiO2CTLfor large area applications using a self-assembly approach
A solution-processed self-assembly method is proposed for forming large-area high-quality CTL films. Owing to the careful control of solvent evaporation, uniform film is formed, leading to enhanced OSC performance. Meanwhile, our method is capable of forming large-area films. This approach can contribute to future low-cost, large-area applications.published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
16
Chen, Lüzhou, e 陈绿洲. "Optical design of organic solar cells by 3-D modeling of device structures". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/196035.
Testo completoAbstract (sommario):
Organic solar cells (OSCs) have attracted intense attention in recent years due to their advantages of low cost, easy fabrication, and high flexibility compared to its inorganic counterparts. However, due to the conflicts between the short diffusion length of excitons and long absorption length of incident photons, the thickness of OSCs is typically thin, and thus power conversion efficiency (PCE) is generally lower than traditional silicon solar cells. Therefore, an exquisite design of light trapping schemes is essential to the PCE improvement. Generally, physical guideline of light trapping involves two main approaches: geometric optics methods and wave optics methods. The former aims at elongating optical path inside the photoactive layer and thus enhancing photon absorption. For organic thin film solar cells with typical active layer thickness of 100 nm-200 nm, which is in subwavelength scale, we cannot investigate light harvesting mechanism simply by the geometric optics methods and instead wave optics properties should be considered.
In this thesis, two different light trapping enhancement designs are proposed. In order to simulate these structures, we built up programs for absorption power calculation based on scattering matrix method (SMM) by rigorously solving Maxwell’s equations. It is worth to point out that, different from the widely-used calculation method by Absorption = 1-Transmission-Reflection, our algorithm can extract the net optical absorption of the active layer rather than the whole OSCs. This improvement is very important because metal absorption, which does not contribute to exciton generation, can be excluded from the result.
In Chapter 3, design of organic solar cell incorporating periodically arranged gradient type active layer is presented. This design can enhance light harvesting with patterned organic materials themselves (i.e. self-enhanced active layer design) to avoid degrading electrical performance in contrast to introducing inorganic concentrators into the active layers such as silicon and metallic nanostructures. Our numerical results show that the OSC with a self-enhanced active layer, compared with the conventional planar active layer configuration, has broadband and wide-angle range absorption enhancement due to better geometric impedance matching and prolonged optical path.
In Chapter 4, OSC with interstitial lattice patterned metal nanoparticles (NPs) is proposed, which can improve the light blocking of traditional square lattice patterned NPs structure and achieve broadband absorption enhancement. Compared to square lattice design, the plasmonic mode couplings between individual NPs in the interstitial lattice are more versatile and much stronger. Moreover, plasmonic modes can couple to the guided modes, resulting in large enhancement factor at some wavelengths. These works provide a theoretical foundation and engineering reference for high performance OSC designs.published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
17
Hultmar, Oscar, Johan Paulsson e Jonathan Sundell. "Mechanical design and construction of solar panel experiment in stratospheric conditions". Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-356131.
Testo completoAbstract (sommario):
This project will be a part of the LODESTAR experiment. LODESTAR is one of the experiments scheduled to fly on the REXUS/BEXUS 26 high altitude balloon flight. The primary objective of the experiment is to investigate the effects of cosmic radiation on CIGS solar cells. The objective of this project is to build a mechanical design that can fulfill all requirements set by the ESA user manual. The mechanical design will first be drawn in mechanical CAD, where the drawing will be constructed from the ESA requirements. Later the design will be simulated in order to choose appropriate materials and a design that can withstand all simulations. Lastly the design will be built according to the drawings and tested according to the simulations. The mechanical design withstood all the simulations and verification tests with no visual deformation, except for the simulation and verification of the drop test. Both the drop simulation and verification test resulted in deformation in one of the aluminium plates. Since this mechanical design is constructed to be used only once, small deformations is within the margin of error. The deformation resulted by the simulation and verification of the drop test matched with a high precision. This is a good confirmation of the results of the drop test. In conclusion, the executed tests gave very promising results. Therefor the design constructed fits all the requirements to travel with solar panels in stratospheric conditions.LODESTAR -BEXUS Project
18
Sheoran, Manav. "Development of high-efficiency solar cells on thin silicon through design optimization and defect passivation". Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/33902.
Testo completoAbstract (sommario):
The overall goal of this research is to improve fundamental understanding of the hydrogen passivation of defects in low-cost silicon and the fabrication of high-efficiency solar cells on thin crystalline silicon through low-cost technology development. A novel method was developed to estimate the flux of hydrogen, released from amorphous silicon nitride film, into the silicon. Rapid-firing-induced higher flux of hydrogen was found to be important for higher defect passivation. This was followed by the fabrication of solar cell efficiencies of ~ 17% on low-cost, planar cast multicrystalline silicon. Solar cell efficiencies and lifetime enhancement in the top, middle, and bottom regions of cast multicrystalline silicon ingots were explained on the basis of impurities and defects generally found in those regions. In an attempt to further reduce the cost, high-efficiency solar cells were fabricated on thin crystalline silicon wafers with full area aluminum-back surface field. In spite of loss in efficiency, wafer thinning reduced the module cost. Device modeling was performed to establish a roadmap towards high-efficiency thin cells and back surface recombination velocity and back surface reflectance were identified as critical parameters for high-efficiency thin cells. Screen-printed solar cells on float zone material, with efficiencies > 19% on 300 μm and > 18% on 140 μm were fabricated using a novel low-cost fabrication sequence that involved dielectric rear passivation along with local contacts and back surface field.
19
Zeng, Lirong Ph D. Massachusetts Institute of Technology. "High efficiency thin film silicon solar cells with novel light trapping : principle, design and processing". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44392.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.Includes bibliographical references.
One major efficiency limiting factor in thin film solar cells is weak absorption of long wavelength photons due to the limited optical path length imposed by the thin film thickness. This is especially severe in Si because of its indirect bandgap. This thesis invents a novel light trapping scheme, the textured photonic crystal (TPC) backside reflector, which can enhance path length by at least several hundred times the film thickness for sufficient absorption. Physical principles and design optimization of TPC are discussed in detail. Thin film Si solar cells integrated with the new back reflector are successfully fabricated and significant efficiency enhancement is demonstrated.The new back reflector combines a one-dimensional photonic crystal as a distributed Bragg reflector (DBR) and reflection grating. The DBR achieves near unity reflectivity in a wide omnidirectional bandgap completely covering the wavelengths needing light trapping, and the grating can diffract light into large oblique angles and form total internal reflection against the front surface of the cell. The unique combination of DBR and grating tightly confines light inside the cell, effectively changing the path length from the thickness of the cell to its width.The back reflector parameters and the antireflection coating are systematically optimized for thin film Si solar cells through simulation and experiments. A 2 [mu]m thick cell can achieve 54% efficiency enhancement using the optimized design.For proof of concept, the TPC back reflector is integrated with thick crystalline Si solar cells (675 [mu]m thick), which demonstrate external quantum efficiency enhancement up to 135 times in the wavelength range of 1000-1200 nm.
(cont.) To prove the theory on the intended application, top-contacted thin film Si solar cells integrated with the TPC back reflector are successfully fabricated using Si-on-insulator material through an active layer transfer technique. All cells exhibit strong absorption enhancement, similar to that predicted by simulation. The 5 [mu]m thick cells gained 19% short circuit current density improvement, despite machine problems during fabrication. The textured photonic crystal back reflector design can be applied directly to single and poly-crystalline Si solar cells, and its principle is broadly applicable to other materials systems.
by Lirong Zeng.
Ph.D.
20
Whyburn, Gordon Patrick. "A simple organic solar cell". Pomona College, 2007. http://ccdl.libraries.claremont.edu/u?/stc,21.
Testo completoAbstract (sommario):
Finding renewable sources of energy is becoming an increasingly important component of scientific research. Greater competition for existing sources of energy has strained the world’s supply and demand balance and has increased the prices of traditional sources of energy such as oil, coal, and natural gas. The experiment discussed in this paper is designed to identify and build an inexpensive and simple method for creating an effective organic solar cell.
21
Cheriton, Ross. "Design and Characterization of InGaN/GaN Dot-in-Nanowire Heterostructures for High Efficiency Solar Cells". Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37905.
Testo completoAbstract (sommario):
Light from the sun is an attractive source of energy for its renewability, supply, scalability, and cost. Silicon solar cells are the dominant technology of choice for harnessing solar energy in the form of electricity, but the designs are approaching their practical efficiency limits. New multijunction designs which use the tunable properties of the more expensive III-V semiconductors have historically been relegated to space applications where absolute power conversion efficiency, resilience to radiation, and weight are more important considerations than cost. Some of the more recent developments in the field of semiconductor materials are the so-called III-nitride materials which mainly use either indium, aluminum or gallium in combination with nitrogen. Indium gallium nitride (InGaN) is one of these III-nitride semiconductor alloys that can be tailored to span the vast majority of the solar spectrum. While InGaN growth traditionally requires expensive substrate materials such as sapphire, three-dimensional nanowire growth modes enable high quality lattice mismatched growth of InGaN directly on silicon without a metamorphic buffer layer. The absorption and electronic properties of InGaN can also be tuned by incorporating it into quantum confined regions in a GaN host material. This opens up a route towards cost-effective, high efficiency devices such as light emitted diodes and solar cells which can operate over a large range of wavelengths. The combination of the two material systems of InGaN/GaN and silicon can marry the low cost of silicon wafers with the desirable optoelectronic properties of III-nitride semiconductors. This thesis investigates the potential for highly nanostructured InGaN/GaN based devices using quantum-dot-in-nanowire designs as novel solar cells which can enable intermediate band absorption effects and multiple junctions within a single nanowire to absorb more of the solar spectrum and operating more efficiently. Such semiconductor nanostructures can in principle reach power conversion efficiencies of over 40\% on silicon, with a cost closer to conventional silicon solar cells as opposed to methods which use non-silicon substrates.
In the primary strategy, the nanowires contain InGaN quantum dots which act as photon absorption/carrier generation centres to sequentially excite photons within the large band gap semiconductor. By using this intermediate band of states, large operating voltages between contacts can be maintained without sacrificing the collection of long wavelength solar photons. In this work, we characterize the properties of such nanowires and experimentally demonstrate sub-bandgap current generation in a large area InGaN/GaN dot-in-nanowire solar cell.
Experimental characterization of InGaN / GaN quantum dots in nanowires as both LEDs and solar cells is performed to determine the nanowire material parameters to understand how they relate to the nanowire device performance. Multiple microscopy techniques are performed to determine the nanowire morphology and contact effectiveness. Optical characterization of bare and fabricated nanowires is used to determine the anti-reflection properties of nanowire arrays. Photoluminescence and electroluminescence spectroscopy are performed. Illuminated current-voltage characteristics and quantum efficiencies are determined. Specular and diffuse reflectivities are measured as a function of wavelength.
Technology computer-aided design (TCAD) software is used to simulate the performance of the overall nanowire device. The contribution from quantum dots or quantum wells is simulated by solving for the carrier wavefunctions and density of states with the quantum structures. The discretized density of states from the quantum dots is modelled and used in a complete drift-diffusion device simulation to reproduce electroluminescence results. The carrier transport properties are modified to demonstrate effects on the overall device performance.
An alternate design is also proposed which uses an InGaN nanowire subcell on top of a silicon bottom subcell. The dual-junction design allows a broader absorption of the solar spectrum, increasing the operating voltage through monolithically grown series-connected, current-matched subcells. The performance of such a cell is simulated through drift-diffusion simulations of a dual-junction InGaN/Si solar cell. The effects of switching to a nanowire subcell based on the nanowires studied in this thesis is discussed.
22
Kamanzi, Janvier. "Thermal electric solar power conversion panel development". Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2527.
Testo completoAbstract (sommario):
Thesis (DTech (Engineering))--Cape Peninsula University of Technology, 2017.The world has been experiencing energy-related problems following pressuring energy demands which go along with the global economy growth. These problems can be phrased in three paradoxical statements: Firstly, in spite of a massive and costless solar energy, global unprecedented energy crisis has prevailed, resulting in skyrocketing costs. Secondly, though the sun releases a clean energy, yet conventional plants are mainly being run on unclean energy sources despite their part in the climate changes and global warming. Thirdly, while a negligible percentage of the solar energy is used for power generation purposes, it is not optimally exploited since more than its half is wasted in the form of heat which contributes to lowering efficiency of solar cells and causes their premature degradation and anticipated ageing. The research is geared at addressing the issue related to unsatisfactory efficiencies and anticipated ageing of solar modules. The methodology adopted to achieve the research aim consisted of a literature survey which in turn inspired the devising of a high-efficiency novel thermal electric solar power panel. Through an in-depth overview, the literature survey outlined the rationale of the research interest, factors affecting the performance of PVs as well as existing strategies towards addressing spotted shortcomings. While photovoltaic (PV) panels could be identified as the most reliable platform for sunlight-to-electricity conversion, they exhibit a shortcoming in terms of following the sun so as to maximize exposure to sunlight which negatively affects PVs’ efficiencies in one hand. On the other hand, the inability of solar cells to reflect the unusable heat energy present in the sunlight poses as a lifespan threat. Strategies and techniques in place to track the sun and keep PVs in nominal operational temperatures were therefore reviewed.
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Chen, Song. "Design, synthesis and characterization of A-D-A structural porphyrin small molecules for bulk heterojunction organic solar cell applications". HKBU Institutional Repository, 2017. https://repository.hkbu.edu.hk/etd_oa/477.
Testo completoAbstract (sommario):
Bulk heterojunction organic solar cells (BHJ OSCs) have been recognized as one of the most promising next generation green technology alternatives to inorganic solar cells because of the low-cost, lightweight, flexibility. Specifically, the use of small molecules instead of polymers as donors in BHJ OSC have been developed very fast recently because small molecules can be facilely synthesized and easily purified, and have a determined molecular structure without batch-to-batch variations. To date, those among the most efficient small molecules were constructed as acceptor-donor-acceptor (A-D-A) structural configuration from electron-rich units such as benzodithiophene (BDT), dithienosilole (DTS), oligothiophene units, and electron-deficient units such as benzothiadiazole (BT), diketopyrrolopyrrole (DPP), isoindigo (IID) and perylenediimide (PDI). Surprisingly, porphyrins were rarely studied either in polymers or π-conjugated small molecules as donor materials, though they have unique chemistry together with excellent photochemical and electrochemical properties, such as facile functionalization of the periphery and the variation of the central atom (metal ions), strong UV-visible absorption, ultrafast photoinduced charge separation in porphyrin-fullerene systems. In this research work, we design, synthesize and characterize new porphyrin-based small molecules with acceptor-donor-acceptor (A-D-A) configuration for bulk heterojunction organic solar cells, and investigate their structure-property relationships, specifically the effect of peripheral and backbone alkyl side-chains, π-conjugated linkers as well as electron-deficient ending units on the charge mobility, film morphology and solar cell performances. In Chapter 1, a general review on the historic and recent development of BHJ OSCs was given first, including the major components and working principle of OSC, the versatile organic semiconductors and their performances in OSCs. In chapter 2, six A-D-A structural porphyrin small molecules were designed and synthesized, in which different peripheral alkyl substitutions are attached to the meso-position of porphyrin core (CS-I, CS-II, CS-III, CS-4, CS-5 and CS-6), and 3-ethylrhodanine is used as terminal group. Their UV-visible absorption in solid, energy level, blend film morphology, charge mobility and cell performance are dependent on the different peripheral substitutions. The active layer consists of these six small molecules as donor materials and PC71BM as the acceptor material with an optimized film thickness. Although all six molecules show similar optical spectrum in solutions, the introduction of linear alkyl side chains can promote thin-film nanostructural order, especially shown to shorten π-π stacking distances between backbones and increase the correlation lengths of both π-π stacking and lamellar spacing, leading to higher efficiency in this serial. Among them, the highest power conversion efficiency of 9.09% has been achieved by CS-4 based devices. In chapter 3, another two new A-D-A porphyrin small molecules (PTTR and PTTCNR) have been developed, which are similar in structure to CS-I, II and III, except that the linker is phenylethynyl in CS-I, II and III, whereas it is terthiophenylethynyl in PTTR and PTTCNR. The highest power conversion efficiency of 8.21% is achieved by PTTCNR, corresponding to a JSC of 14.30 mA cm−2, VOC of 0.82 V, and FF of 70.01%. The excellent device performances can be ascribed to the conjugated structure of porphyrin with 3,3''-dihexyl-terthiophene and the aliphatic 2-octylundecyl peripheral substitutions, which not only effectively increase the solar flux coverage between the conventional Soret and Q bands of porphyrin unit, but also optimize molecular packing through polymorphism associated with side-chain and the π-conjugated backbones, and form the blend films with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) characteristics of bi-continuous, interpenetrating networks required for efficient charge separation and transportation.;In chapter 4, we designed and synthesized a new dimeric porphyrin donor molecule (CS-DP) containing A-π2-D-π1-D-π2-A architecture by coupling of two zinc porphyrin cores through ethynyl linker. Interestingly, it can harvests the photons up to deep near-infrared (NIR) region in the absorption spectrum. From the past decades, it has been found that developing donor molecules with the absorption spectral in NIR region is a challenging key factor to get the high performance BHJ OSCs. Solar cell devices employing CS-DP as a donor exhibit a highest power conversion efficiency of 8.23%, corresponding to JSC = 15.14 mA cm-2, VOC = 0.781 mV and FF = 69.8% under AM 1.5G solar radiation. The high efficiency of this molecule is attributed to a panchromatic IPCE action spectrum from 300 nm to 1000 nm. Also, this performance is best for the reported deep NIR organic solar cells based on single small molecule and PC71BM system so far. We envision that this new small bandgap dimeric porphyrin is very promising to use in ternary and multi-junction applications as well as NIR photodetectors. In chapter 5, a series of new A-D-A structural porphyrin small molecules (CS-10, CS-11 and CS-12) have been prepared, that contain the same meso-thienyl-thioalkyl substituted porphyrin core and 3-ethylrhodanine ending unit, but varies with different numbers of phenylethynyl linker. Using them as donors for solution-processed organic solar cells, the device based on CS-10 featuring single phenyl ethynyl π-linker exhibits high power conversion efficiency (PCE) of 7.0%. The results indicate that meso-thienyl-thioalkyl substitution and controlled π-linker length is beneficial to tune the optoelectronic properties, film morphology and consequently performance of porphyrin-based BHJ OSCs. In chapter 6, two symmetrical tetra-meso-substituted porphyrin molecules (ZnP and CuP) have been prepared in gram-scale through the direct condensation of pyrrole and 4-[bis(4-methoxyphenyl)amino]benzaldehyde. Its Zn(II) and Cu(II) complexes exhibit excellent thermal and electrochemical stability, specifically, high hole mobility and very favorable energetics for hole extraction that render them attractive for implementation as new hole transporting materials in organometallic halide perovskite solar cells (PSCs). As expected, the use of ZnP as HTM in PSCs affords a competitive PCE of 17.78%, which is comparable to the most powerful HTM of Spiro-OMeTAD (18.59%) under the same working conditions. Meanwhile, the metal centers affect somewhat the photovoltaic performances that CuP as HTM produces a relative lower PCE of 15.36%. Notably, the perovskite solar cells employing ZnP show longer stability than that of Spiro-OMeTAD. Moreover, the two porphyrin-based HTMs can be prepared from relatively cheap raw materials with a facile synthetic route. The results demonstrate that ZnP and CuP can be a new class of HTMs for efficient and stable perovskite solar cells. To the best of our knowledge, this is the highest performance for porphyrin-based perovskite solar cells with PCE > 17%. The dissertation was completed with conclusions and outlooks in chapter 7.
24
Panse, Pushkaraj. "Copper Gallium Diselenide Solar Cells: Processing, Characterization and Simulation Studies". [Tampa, Fla. : s.n.], 2003. http://purl.fcla.edu/fcla/etd/SFE0000080.
Testo completo
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Giatti, Brandon. "Optical Properties of Nanostructured Dielectric Coatings". PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1940.
Testo completoAbstract (sommario):
Solar cells have extrinsic losses from a variety of sources which can be minimized by optimization of the design and fabrication processes. Reflection from the front surface is one such loss mechanism and has been managed in the past with the usage of planar antireflection coatings. While effective, these coatings are each limited to a single wavelength of light and do not account for varying incident angles of the incoming light source. Three-dimensional nanostructures have shown the ability to inhibit reflection for differing wavelengths and angles of incidence. Nanocones were modeled and show a broadband, multi-angled reflectance decrease due to an effective grading of the index.
Finite element models were created to simulate incident light on a zinc oxide nanocone textured silicon substrate. Zinc oxide is advantageous for its ease of production, benign nature, and refractive index matching to the air source region and silicon substrate. Reflectance plots were computed as functions of incident angle and wavelength of light and compared with planar and quintic refractive index profile models. The quintic profile model exhibits nearly optimum reflection minimization and is thus used as a benchmark. Physical quantities, including height, width, density, and orientation were varied in order to minimize the reflectance. A quasi-random nanocone unit cell was modeled to better mimic laboratory results. The model was comprised of 10 nanocones with differing structure and simulated a larger substrate by usage of periodic boundary conditions. The simulated reflectance shows approximately a 50 percent decrease when compared with a planar model. When a seed layer is added, simulating a layer of non-textured zinc oxide, on which the nanocones are grown, the reflectance shows a fourfold decrease when compared with planar models. At angles of incidence higher than 75 degrees, the nanocone model outperformed the quintic model.
26
Lambert, Darcy Erin. "Nanostructured Extremely Thin Absorber (ETA) Hybrid Solar Cell Fabrication, Optimization, and Characterization". PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/637.
Testo completoAbstract (sommario):
Traditional sources of electrical energy are finite and can produce significant pollution. Solar cells produce clean energy from incident sunlight, and will be an important part of our energy future. A new nanostructured extremely thin absorber solar cell with 0.98% power conversion efficiency and maximum external quantum efficiency of 61% at 650 nm has been fabricated and characterized. This solar cell is composed of a fluorine-doped tin oxide base layer, n-type aluminum doped zinc oxide nanowires, a cadmium selenide absorber layer, poly(3-hexylthiophene) as a p-type layer, and thermally evaporated gold as a back contact. Zinc oxide nanowire electrodeposition has been investigated for different electrical environments, and the role of a zinc oxide thin film layer has been established. Cadmium selenide nanoparticles have been produced and optimized in-house and compared to commercially produced nanoparticles. Argon plasma cleaning has been investigated as a method to improve electronic behavior at cadmium selenide interfaces. The thermal anneal process for cadmium selenide nanoparticles has been studied, and a laser anneal process has been investigated. It has been found that the most efficient solar cells in this study are produced with a zinc oxide thin film, zinc oxide nanowires grown under constant -1V bias between the substrate material and the anode, cadmium selenide nanoparticles purchased commercially and annealed for 24 hours in the presence of cadmium chloride, and high molecular weight poly(3-hexylthiophene) spin-coated in a nitrogen environment.
27
Howells, Calvyn T. "Material and device design for organic photovoltaics". Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/6810.
Testo completoAbstract (sommario):
This thesis presents novel materials for photovoltaic conversion. The materials described are solution-processable organic semiconductors and have been used in the fabrication of organic photovoltaic cells (OPVs). The widely used PEDOT:PSS layer was investigated in P3HT and PTB7 photovoltaics. By doping, the efficiencies recorded were amongst the highest reported in the field using a conventional architecture. Two low band-gap BODIPY-based polymers were introduced and shown to have properties favourable for optoelectronics. Photovoltaics consisting solely of the polymers as the active component surpassed the performance expected without the use of an acceptor, indicating ambipolar behaviour, which was verified by charge carrier mobility measurements. When blended with an acceptor, the devices demonstrated a short-circuit current density similar to that of P3HT, a well-studied and successful OPV material. They also revealed a broad spectral response and were shown to operate as photodiodes. Two small molecules containing diketopyrrolopyrrole (DPP) and BODIPY were introduced and characterised. The addition of thiophenes red shifted the absorption but did not result in a sufficient bathochromic shift. Instead, a propensity to aggregate limited the performance. PLQY measurements showed the aggregation to quench luminescence. The study demonstrated the importance of controlling aggregation for efficient devices. Two solution-processable small molecules with a germanium-bridged spiro centre were investigated, and the molecular, electrochemical and optical properties discussed. The small molecule with shorter conjugation length exhibited an interesting packing motif shown to be favourable for charge transport. The mobility measurements were an order of magnitude higher than those reported for sexithiophene, a small molecule analogue, and the same order of magnitude as P3HT. The two-dimensional charge transporting nature of the material was verified with two independent techniques: time of flight (TOF) and organic field-effect transistor (OFET) measurements. The mobility of the material was found to vary with annealing, a result of morphological changes. These were studied with optical, electron and scanning probe microscopies. By controlling the morphology with the implementation of a well-defined annealing method, it was possible to improve the performance of OFETs and planar-heterojunction OPVs. Solution-processed bulk-heterojunction OPVs were fabricated, characterised and optimised with Ge spiro molecules. A PCE similar to that of P3HT, 2.66 %, was achieved for the one, whilst a PCE of 1.60 % was obtained for the other. The results are encouraging, and there is scope for improvement by increasing the overlap between the absorption and solar spectrum, for example.
28
Thibert, Sébastien. "Etude de la métallisation de la face avant des cellules photovoltaïques en silicium". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI025/document.
Testo completoAbstract (sommario):
À l'échelle industrielle, la métallisation de la face avant des cellules photovoltaïques est réalisée grâce au procédé de sérigraphie depuis plus de 40 ans. Une pâte à base d'argent est imprimée avant d'être recuite à haute température. La robustesse, la simplicité et la haute cadence de production de ce procédé ont largement contribué à son succès. L'étape de métallisation est critique dans la chaîne de fabrication des cellules. D'un côté, les propriétés des contacts déposés déterminent les performances finales des cellules. D'un autre côté, plus de 7% de la consommation mondiale d'argent sont déjà destinés à l'industrie photovoltaïque. Avec les prévisions de croissance exponentielle de ce secteur, la quantité d'argent déposée lors de cette étape devient de plus en plus cruciale car elle régit le coût final des cellules. Elle dépend également de la qualité des contacts imprimés. Il est donc important d'optimiser le procédé de sérigraphie pour limiter la masse d'argent imprimée et maximiser le rendement des cellules. Les travaux présentés dans la première partie de cette thèse sont focalisés sur ces deux aspects. Dans un premier temps, le comportement rhéologique des pâtes de sérigraphie est étudié. Par la suite, une étude multifactorielle combinée à des simulations des pertes de puissance permet d'évaluer l'influence des paramètres de la sérigraphie sur le rendement des cellules et la masse d'argent déposée. Ces travaux ont conduit à la fabrication de cellules caractérisées par un rendement moyen de 19,0% à l'échelle industrielle. Le procédé de sérigraphie reste couteux et de nombreuses solutions alternatives sont à l'étude. En effet, la microstructure hétérogène des contacts cause des pertes électriques non négligeables en comparaison des cellules à haut rendement. Par ailleurs, la résolution limitée de ce procédé ne permet plus de réduire les dimensions des impressions, ce qui a un impact direct sur les pertes optiques et la masse d'argent déposée. Enfin, l'optimisation simultanée des propriétés électriques et géométriques des contacts complexifie son contrôle à l'échelle industrielle. Le concept double couche est une alternative innovante qui permet de s'affranchir de ces limitations. Une première couche est d'abord imprimée pour limiter la largeur initiale des contacts et améliorer l'interface avec la cellule. Une seconde couche de métal pur, déposée par voie électrolytique, vient épaissir cette dernière pour optimiser la hauteur et la conductivité de la grille de métallique. Dans le même temps, cette étape permet de contrôler précisément la masse d'argent déposée. Plusieurs solutions sont disponibles pour réaliser l'impression de la première couche. Grâce à sa flexibilité et à sa très haute cadence de production, le procédé de flexographie semble répondre au cahier des charges d'un tel dépôt dans des conditions industrielles. La seconde partie des travaux exposés dans cette thèse traite du développement de cette technique d'impression. Tout d'abord, le comportement rhéologique de plusieurs encres dérivées d'une pâte de sérigraphie classique est étudié. Dans un second temps, le procédé de flexographie est adapté au dépôt de lignes pouvant être épaissies par voie électrolytique (procédé LIP). Le potentiel de ce procédé est ensuite évalué à l'aide de modélisations du rendement et de la masse d'argent déposée. Finalement, la faisabilité du concept est démontrée grâce à la fabrication d'une cellule caractérisée par un rendement prometteur de 17,9%At an industrial scale, the front side metallization of solar cells is performed by screen printing for 40 years. A silver-based paste is printed before a high temperature annealing. This simple and robust process enables a high throughput. However, the metallization is a critical step in production lines. On the one hand, the contact properties affect the final cell performances. On the other hand, the photovoltaic industry already accounts for 7% of the world's silver consumption. With the expected exponential growth of this sector, the mass of silver per cell becomes crucial as it governs their final cost. Consequently, it is mandatory to optimize the screen printing process to limit the amount of deposited silver and maximize the solar cell efficiency. The first part of this study focused on these two aspects. First, the rheological behavior of screen printing pastes is investigated. Then, a multifactorial study is combined with power loss simulations to assess the effect of screen printing parameters on the cell efficiency and the deposited silver mass. Besides, these studies have lead to an average cell efficiency of 19,0% at an industrial scale. To ensure the photovoltaic industry growth, the screen printing process should be replaced in coming years. Indeed, the heterogeneous contact microstructure causes significant electrical losses in comparison to high-efficiency cells. Moreover, the limited resolution of this process does no longer allow a contact width reduction, which has a direct impact on the optical losses and the silver mass per cell. Finally, the simultaneous optimization of the electrical and geometrical contact properties is difficult at an industrial scale. The seed and plate concept is an innovative solution that overcomes these limitations. First, a seed layer is printed to reduce the initial contact width and improve its interface with the cell. Then, a second layer is electrolytically grown to improve the conductivity and the height of the metal grid. Besides, this step enables an accurate control of the deposited silver amount. Several solutions are available to print the first layer. Because of a high throughput and flexibility, the flexographic printing process seems particularly well suited to meet the seed layer requirements at an industrial level. The second part of this study focuses on the development of this process. First, the rheological behavior of several inks is studied. Secondly, the flexographic printing process is adapted to print fine lines that can be thickened by light induced plating (LIP). The potential of this metallization scheme is then assessed using a simulation of cell performances and silver consumption. Finally, a promising 17,9% cell efficiency demonstrates the concept feasibility
29
Davidsson, Oscar, e Marcus Obrelius. "Faktorer och aspekter att beakta vid solcellsinstallationer". Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-86906.
Testo completoAbstract (sommario):
Människans energianvändning måste förändras. Mer än 80 % av den primära energianvändningen är i dagsläget baserad på fossila bränslen. För att uppnå en mer hållbar klimatutveckling måste en större del av energianvändningen framställas av förnybara energikällor, exempelvis solenergi. Syftet med denna studie är att exemplifiera praktiska, tekniska, ekonomiska samt arkitektoniska faktorer och aspekter som bör tas i beaktande vid solcellsinstallationer i en bebyggelse. Genom en fallstudie undersöktes Sankt Sigfridområdet i Växjö. Fallstuiden avgränsades till fyra fastigheter med möjlig solcellsinstallation samt en möjlig solcellspark. Genom teoretiska utgångspunkter, studiebesök, observationer, solstudie samt tekniska- och ekonomiska beräkningar bedömdes solcellers möjliga elproduktion och potentiella besparing. Integreringsförslagen tog fram utifrån anskaffad teori och en surveyundersökning med utgångspunkt i hur byggnaders gestaltning påverkas vid en solcellsinstallation. Med dagens generösa statliga subventionsmedel finns möjlighet till en ekonomisk lönsamhet vid en solcellsinvestering, vilket återspeglas i resultatets besparingsberäkning. Fallstudien påvisar även komplexiteten vid solcellsinstallationer samt hur olika praktiska, tekniska, ekonomiska och arkitektoniska faktorer och aspekter komplicerar integreringen i en bebyggelse.The global energy use must change, more than 80 % of the primary energy use is currently based on fossil fuels. To achieve a more sustainable development, a larger part of the energy consumption must be produced from renewable energy sources, such as solar energy. The purpose of this study is to exemplify practical, technical, economical and architectural factors and aspects that should be taken into consideration regarding solar cell integration in buildings. Through a case study, the Sankt Sigfrid area in Växjö was examined and bounded to four properties with possible solar cell installation as well as a possible solar cell park. Through theory, study visits, observations, solar study as well as technical and economical calculations, the solar cells' possible electricity production and potential savings were demonstrated. The integration proposals were compiled through the obtained theory and a survey based on how the design of building objects is affected by a solar cell installation. With today's generous government subsidies, there is a possibility of economic profitability regarding solar cell investments, which is reflected in the profit calculation of the result. The case study also demonstrates the complexity of solar cell installations as well as how various practical, technical, economical, architectural factors and aspects complicate the integrations onto buildings.
30
Pokorný, Marek. "Charakterizace vlastností fotovoltaického systému". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219073.
Testo completoAbstract (sommario):
The aim of this work is informed first about photovoltaics universally, works to inform the photovoltaic panels and complete plants. The work also includes instructions on how to implement PVP in accordance with law. Another part is the rough draft of the photovoltaic power 30 kWp, which can be placed on the house, computation and calculation of investment and them profitable investments to time. Design is made in two separate forms of the Fronius Solar and Sunny Design, their outputs are compared. The practical part of this work cooperates with the company SOLARTEC Ltd. for experimental measurements of the photovoltaic system and develop a methodology for setting the properties of real solar systems in operation from the measured data then stored in a database. These data further evaluate and compare the similar operating conditions. This data will show as the course of production of electricity during the typical day in percentage terms, depending on the incident irradiance, cell temperature, angle of incident radiation, etc. We can compare what it looks like an ideal day in terms of production of photovoltaic power, with the other days. Further are in work mentioned histograms achievement panel behind classical day and behind all - time investigation.
31
Greer, Michael R. "A 6% efficient MIS particulate silicon solar cell". Thesis, 1998. http://hdl.handle.net/1957/34037.
Testo completo
32
Fangsuwannarak, Thipwan Photovoltaic & Renewable Energy Engineering UNSW. "Electronic and optical characterisations of silicon quantum dots and its applications in solar cells". 2007. http://handle.unsw.edu.au/1959.4/44340.
Testo completoAbstract (sommario):
In this thesis, the structural, optical and electrical properties of crystalline silicon quantum dots (SiQDs) are examined for application to silicon based tandem cells. The approach has been to concentrate on all silicon devices by taking advantage of quantum confinement in low-dimensional Si. RF magnetron co-sputtering provided the capability of creating superlattice structures in conjunction with high temperature annealing, to form Si nanocrystals in an oxide matrix. Structural techniques, including Fourier transform infrared spectroscopy (FTIR), micro-Raman spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Secondary ion mass spectroscopy (SIM) were employed to gather structural information about the SiQD/SiO2 SLs. The result combine presents that the packing density of Si QDs, correlated to the oxygen content of the silicon rich oxide layer can be control independently. The effect of Si nanocrystallite density on Raman scattering is investigated. The preliminary results present that a decrease in the oxygen content (x) results in an increased sharpness of the Strokes-mode peak of nanocrystalline Si, attributed to an increase in the proportion of crystalline Si because of the increased number of SiQDs. However the influence of the surface region on the crystallite core intensity scattering becomes dominant, when SiQD size diameter is very small (less than 3 nm). The present work shows that a decrease in x-content leading to an increase of the SiQD concentration, initially results in the enhancement of the lateral conductivity in the SiQD superlattice material. In this work, the Al contacting scheme, using a prolonged heat treatment technique at elevated temperature less than the eutectic point of Al and Si (577C) has been successfully applied to making Ohmic contacts on both SiQD SLs in oxide and nitride matrices. Activation energy (Ea) of SiQDs, extracted from a linear Arrhenius plot is investigated in the present work in order to expand the understanding of engineering electrical injection in laterally active paths. It is found that a lower barrier height of dielectric matrix influences to the lateral electron transport of the SiQDs in such dielectric matrix. PL results confirm that the band gap of surface oxidized SiQDs widens due to quantum confinement. The present results reveal that the strong peak (Q-peak) due to quantum confinement is more effective in the emission with increasing SiQD concentration. The surface oxide is believed to play an important role in the reduction of SiQD luminescence due to a trapped exiciton. It is concluded that SiQDs surface oxide accompanied by a SiO2 matrix may not provide a good passivation in very small SiQD size. However the energy band gap and conductivity of the SiQDs are tunablity, in the optimum range of SiQD size and concentration. This observation may be important for future nanoelectronics applications.
33
Pillai, Supriya School of Photovoltaic & Renewable Energy Engineering UNSW. "Surface plasmons for enhanced thin-film silicon solar cells and light emitting diodes". 2007. http://handle.unsw.edu.au/1959.4/40877.
Testo completoAbstract (sommario):
Photovoltaics (PV) is fast emerging as an attractive renewable energy technology due to concerns of global warming, pollution and scarcity of fossil fuel supplies. However to compete in the global energy market, solar cells need to be cheaper and more energy efficient. Silicon is the favorite semiconductor used in solar photovoltaic cells because of its ubiquity and established technology, but due to its indirect bandgap silicon is a poor absorber and light emitter. Thin film cells play an important role in low cost photovoltaics, but at the cost of reduced efficiencies when compared to wafer based cells. There remains much untapped potential in thin-film solar cells which this work has attempted to exploit through exploring novel approaches of enhancing the efficiency of thin film cells using the optical properties of sub-wavelength metal nanoparticles. Metals are considered as strong absorbers of light because of their large free-electron density. How can metals improve light trapping in solar cells? This question has raised several eyebrows and this thesis is an attempt to show that metal nanoparticles can be useful in producing efficient solar cells. Subwavelength metal particles support surface modes called surface plasmons when light is incident on them, which cause the particles to strongly scatter light into the underlying waveguide or substrate, enhancing absorption. The process of coupling thin film silicon waveguide modes to plasmonic metals using unpolarised light at normal incidence is applied to silicon-based solar cells and light emitting diodes, and enhanced photocurrent and electroluminescence is realized with potential for further optimisation and improvement. The results from this study correspond to a current increase of up to 19% from planar wafer based cells and up to 33% increase from 1.25 micron thin-film silicon-on-insulator structures for the AM1.5 global spectrum. We also report for the first time an up to twelve fold increase in electroluminescence signal from 95nm thick light-emitting diodes. From the results we conclude that this method which involves simple techniques of nanoparticle deposition and characterization could hold important implications in the improvement of thin-film silicon cell absorption / emission efficiencies where conventional methods of light trapping are not feasible, resulting in promising near-term applications of surface plasmons in photovoltaics and optoelectronics.
34
Chang, Wan-Rou, e 張婉柔. "Optimized Design of Novel Silicon Thin Film Solar Cells". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/80939121432508470844.
Testo completoAbstract (sommario):
碩士國立中山大學
電機工程學系研究所
101
In this work, combining the advantages of amorphous silicon and microcrystalline silicon, we propose a new structure of solar cell “ ITO / p-a-Si:H / i1-a-Si:H / i2-μc-Si:H / n-μc-Si:H / ITO ”. The i1-a-Si:H can make the open circuit voltage much higher due to the high mobility bandgap. The i2-μc-Si:H can get more effectively absorb of sunlight, so the novel p-i1-i2-n solar cell can get higher short circuit current density. The simulation results indicate the conversion efficiency is higher than that of the conventional silicon solar cell at least 8.8 % to 19.5 %. In order to obtain low-cost and high-performance solar cell, a novel thin film solar cell fabrication has been developed. In this way, the deposition of silicon thin film solar cells on both sides of the substrate is performed at the same time, forming a back-to-back parallel-type silicon thin film solar cell naturally. The simulation results indicate the conversion efficiency of the back-to-back parallel-type amorphous silicon thin film solar cell is higher than that of the conventional amorphous silicon thin film solar cell at least 39 %. And the conversion efficiency of the back-to-back parallel-type microcrystalline silicon thin film solar cell is higher than that of the conventional microcrystalline silicon thin film solar cell at least 16 %. The fabrication results also indicate the conversion efficiency is higher than that of the conventional pin amorphous silicon solar cell at least 25.6 % to 31.5 %.
35
Chen, Wei. "Modeling, design and fabrication of thin-film microcrystalline silicon solar cells". Thesis, 2000. http://library1.njit.edu/etd/fromwebvoyage.cfm?id=njit-etd2000-013.
Testo completo
36
Logiudice, Vito. "Design, fabrication and testing of silicon interdigitated back contact (IBC) solar cells". Thesis, 1993. http://spectrum.library.concordia.ca/2974/1/MM87320.pdf.
Testo completo
37
Chao, Tse-Min, e 趙澤民. "Design, Simulation and Characterization of Thin Film Amorphous Silicon Based Solar Cells". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/15786669219945898710.
Testo completoAbstract (sommario):
碩士國立臺灣大學
電子工程學研究所
100
In this thesis, we used TCAD program to simulate and design the amorphous silicon based solar cells. According to simulation results, the optimization of solar cell design and related physical mechanism can be obtained. The simulated illumination current-voltage characteristics of single junction a-Si:H and μc-Si:H were compared to experimental results for verifying the accuracy of material parameters. Based on the analysis of realistic thin film Si solar cells, the optimizations of surface textures were done and some discussions were given. It turned out that the change of built-in electric field will affect the generated short-circuit current more significantly in a high aspect ratio texture structure. The multi-junction solar cell design was considered as a way to increase the conversion efficiency. The analysis and design of an intermediate reflector layer inserted between a-Si:H and μc-Si:H were done. Two triple-junction a-Si:H based solar cells were simulated and their texture optimizations were given as well. The current mismatch effect of the micromorph tandem cell caused by spectrum variations was discussed. According to the characterizations of a-Si:H based cells under high temperature conditions, polymorphous silicon was found to have a similar temperature coefficient like a-Si:H. The simulation results of the micromorph tandem cell under low irradiance conditions showed consistent trend with experimental results. Through experiments on degradation and recovery of single junction a-Si:H and the micromorph cells, it is found that the micromorph cell had minor light-induced degradation and enhanced recovery compared to single junction a-Si:H cell. The reason of this enhanced recovery and its physical mechanism were discussed.
38
Chen, Yung-Chin, e 陳永金. "Design and Fabrication of Anti-reflection Coating for Amorphous Silicon Solar Cells". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/98792836958852674607.
Testo completoAbstract (sommario):
碩士正修科技大學
電子工程研究所
95
The reflectance on the device surface influences greatly the energy conversion efficiency of solar cell and should be considered as an important topic concerned with the practical use of solar cells. We use the technique of AR coatings (anti-reflectance coatings) to lessen the influence of reflectance and therefore to increase the transmittance of illuminating light. In this paper, it will study the anti-reflectance coatings to affect conversion efficiency of amorphous solar cell. First, the properties of anti-reflection (AR) coatings in the visible light were simulated by Fresnel’s theory and FilmStar software. It was quested result of the optimum design. The materials of silicon oxide、 oxynitride and nitride were deposited on the glass by using low-temperature plasma enhanced chemical vapor deposition (PECVD) method. This three materials were low cost and good quality of film by low- temperature depositing. The thickness and refractive index of the deposited films were measured by spectroscopic Ellipsometery. And it was used FTIR to probe into the bonding configuration under different flow of materials. The reflectance spectra of the AR coatings were measured by UV-VIS spectrophotometer. it was analyzed result of design and measure. An optimal reflectance spectrum of the AR coating was simulated with the three-layer[SiON 1.65(72.72nm)/SiNx 2.01(114.67nm)/SiO2 1.46(86.1nm)] structure by FilmStar software. According to the results of experiment, an experimental reflection of 5.27(%) and an experimental short-circuit current density of 16.634(mA/cm2) were obtained for the three layer of anti-reflection coatings. Therefore, the conversion efficiency of amorphous silicon solar cells can be effectively increased with the three-layer AR coating.
39
Kao, Chi-wei, e 高啟瑋. "Design and Process Development of Poly-crystalline Silicon Thin Film Solar Cells". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/05676266390989885057.
Testo completoAbstract (sommario):
碩士國立雲林科技大學
電子與資訊工程研究所
93
This work has studied on the poly-crystalline silicon thin film solar cell process development. Baseline process flow of the thin film solar cell has been designated to achieve high conversion efficiency. Basically, Via hole Etching for the Separation of Thin film (VEST) structure is used for the solar cells which not only is of modular process but also can reduce the manufacturing cost. This work utilized LPCVD to deposit poly-crystalline silicon thin film on a single-crystalline silicon wafer with a thin SiO2 film on it. Thermal evaporation was used to deposit Al thin film on the poly-crystalline silicon thin film and then annealed with a phosphorous doping disk for the gettering. The phosphorous atoms can getter the impurities from the p-type silicon substrate to have a purer substrate. RIE was then used to etch Via-hole structure in the poly-Si film. Besides, antireflection coating of SiO2 layer has been used to reduce the light reflection on the cell surface and to increase the light absorption. This work used thermal annealing to replace the ZMR, which has proved that the grain size and the surface roughness became larger and the surface became smoother with increased anneal temperature and anneal time. This work used boron or phosphorous doping disk for the solid-source thermal diffusion and doped impurities in the solar cell. The solar spectrum on earth’s surface has larger intensity for the shorter wavelengths. In order to collect the photo-carriers generated by the short-wavelength light and to reduce the carrier recombination, a shallow junction is required for the solar cells. Simulation by PC1D in this work, efficiency can be achieved as high as 8.2% for the VEST solar cells. VEST cells with further passivation process can achieve a efficiency of 10%.
40
Wu, HsinYu, e 吳欣諭. "Design And Characterization Of Back Electrode Applied For Silicon Thin Film Solar Cells". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/85714087059067719954.
Testo completoAbstract (sommario):
碩士明道大學
材料科學與工程學系碩士班
100
In this study, different back contact (Ag, AlTi, AlCrTi) were deposited by DC magnetron sputtering under different power, Ar gas flow rate and pressure. The effect of sputtering deposition parameters on optical, electrical and structural properties of back contact was carried out by four-point probe method, UV-vis spectrometer and scanning electron microscope. This research also adopted the thin film optical simulation software, TracePro, to find the suitable material for reflection layer, and investigate the optical properties. The results showed that using Ag, AlTi and AlCrTi as the electrode of GAZO shows ohmic characteristics. A low contact resistance of 1.57×10-3 ohm for the AlTi back electrode was observed by the Transmission Line Model (TLM) system. After optimizing the deposition parameters of AlTi thin films as a back contact for silicon thin film solar cells, the best solar cell showed the performance of an open-circuit voltage Voc of 0.856 V, short-circuit current density Jsc of 14.43 mA/cm2, fill factor of 0.70 and maximum efficiency of 8.59%. The AlTi back contact was suitable to replace Ag back contact for the production cost down in silicon thin film solar cell fabrication.
41
Sahoo, Kartika Chandra, e Kartika. "Design and Fabrication of Sub-wavelength Structures on Silicon Nitride for Solar Cells". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/63970518523390420268.
Testo completoAbstract (sommario):
博士國立交通大學
材料科學與工程系所
98
In this dissertation, we numerically study the reflectance of sub-wavelength structures on silicon nitride for solar cell application. Based on the numerical study, we develop a fabrication method to form the sub-wavelength structures on silicon nitride surface for solar cells. Since silicon nitride is a well known antireflection coating used in semiconductor industry, we explore the texturization on silicon nitride antireflection coating and its optical properties. The main motivation behind this lies in the fact that the sub-wavelength structures will act as a second antireflection coating layer with an effective refractive index so that the total structure can perform as a double layer antireflection coating layer. Thus, we could cost down the deposition of second antireflection coating layer can be saved with better or comparable performance as that of a double layer antireflection coating solar cell. In this study, we calculate the spectral reflectivity of pyramid-shaped silicon nitride sub-wavelength structures. A multilayer rigorous coupled-wave approach is advanced to investigate the reflection properties of silicon nitride sub-wavelength structure. We examine the simulation results for single layer antireflection and double layer antireflection coatings with sub-wavelength structure on silicon nitride surface, taking into account effective reflectivity over a range of wavelengths and solar efficiency. The results of our study show that a lowest effective reflectivity of 3.43% can be obtained for the examined silicon nitride sub-wavelength structure with the height of etched part of silicon nitride and the thickness of non-etched layer of 150 nm and 70 nm, respectively, which is less than the results of an optimized 80 nm silicon nitride single layer antireflection coating (~ 5.41%) and of an optimized double layer antireflection coating with 80 nm silicon nitride and 100 nm magnesium fluoride (~5.39%). 1% cell efficiency increase is observed for the optimized Si solar cell with silicon nitride sub-wavelength structure, compared with the cell with single layer silicon nitride antireflection coatings; furthermore, compared with double layer antireflection coated solar cell, the increase is about 0.71%. The improvement on the cell efficiency is mainly due to lower reflectance of silicon nitride sub-wavelength structure over a wavelength region from 400 nm to 600 nm that leads to lower short circuit current. Based upon our theoretical calculation of improved efficiency of silicon solar cell with silicon nitride sub-wavelength structures, we have developed a simple and scalable approach for fabricating sub-wavelength structures on silicon nitride by means of self-assembled nickel nano particle masks and inductively coupled plasma ion etching. The size and density of nickel nano particles are controlled by the initial thickness of nickel film that will be annealed to form the nano-particles on the silicon nitride film deposited on the silicon substrate. Inductively coupled plasma etching time is responsible for controlling the height of the fabricated silicon nitride sub-wavelength structure on silicon substrate. Nevertheless, the surface profile of a sub-wavelength structure is strongly dependent on the conditions of the reactive ion etching process. So, we have also investigated the effect of inductively coupled plasma etching conditions on the profile of fabricated sub-wavelength structure on Silicon nitride antireflection coating layers. At last, we succeeded in fabrication of nanopillar structures and nanocone structures on silicon nitride surface by one step and two step inductively coupled plasma etching methods. The relationship of etching time with structure height and average reflectance spectra has been drawn. In summary, design and fabrication of sub-wavelength structures on silicon nitride antireflective surface was investigated for the first time. The structure height and non-etched part of silicon nitride has been optimized for lowest effective reflectance by theoretical calculation using rigorous coupled wave analysis method. Also the shape effect has been studied theoretically. Based on theoretical results, the nanopillar and nanocone structures on silicon nitride surface have been fabricated successfully using self-assembled nickel nano clusters and inductively coupled plasma etching method. The achieved low reflectance is believed to be useful to improve the efficiency of solar cells. Also, the preliminary results for a silicon solar cell has been obtained using silicon nitride sub-wavelength structure, which shows a great promise in improvement of efficiency compared with a single layer antireflection coating.
42
"Growing Cu(In,Ga)Se₂ thin film solar cells with high efficiency and low production costs". 2012. http://library.cuhk.edu.hk/record=b5549502.
Testo completoAbstract (sommario):
銅銦鎵硒薄膜太陽能電池因為其高效率及相對低廉的成本，商業應用已經開始陸續出現。我們自主研發的集成式銅銦鎵硒薄膜電池生產系統可以全程製作襯底大小為10cm x 10cm 的電池及剃型組件。本研究工作主要分為兩個方向:第一個方向是研究及測試生長高效率太陽能電池及組件的具體條件。通過儀器改進及電池每層鍍膜的條件優化，能夠重複的生長高效率電池及組件; 第二個方向是通過減少銅銦鎵硒吸光習的厚度從而達到降低電池生產成本的目的。銅銦鎵硒採用三步共蒸法製備吸收層。第一步先蒸發銦、鎵、硒三種元素形成n型硒化銦(鎵)薄膜;第二步蒸發銅、硒形成銦鎵硒半導體薄膜; 第三步蒸發一層額外的型硒化銦(鎵)薄膜保證整體電池是p型半導體。三步期間的襯底溫度經過小心調試，以使得合適的鎵梯度能夠在吸收層裹形成。通過每一層的條件優化我們能夠生長出高光電轉換效率的太陽能電池(17%)及組件(12%)。
太陽能電池的變溫測試及弱光測試對瞭解其應用潛能存在非常重要的作用。通過多組對比實驗發現銅銦鎵硒電池的溫度係數可以通過增加鎵在吸收層的組分而得到改善。同時，電池的弱光表現可以通過減少銅的量得到很大的提高。STM 的研究發現弱光表現得到改善是因為吸收層顆粒介面電阻的增加而導致的。
減少吸收層的厚度有利於進一步減少太陽能電池的材料成本。當電池的吸收層厚度小於一微米時，開路電壓跟短路電流都明顯有所減少，從而導致太陽能電池效率降低。更薄電池效率的提高可以從兩個方面來實現:氧化鋅表面的陷光結構及更加合適的鎵含量的使用。通過這兩艇改進方法，電池效率被提高到14%以上，使得超薄電池有更好的應用前景。
Cu(In,Ga)Se₂ (CIGS)-based thin film solar cell has been commercialized recently due to its high energy conversion efficiency. We have designed an integrated satellite deposition system for producing CIGS solar cell with substrate size of 10cm x 10cm. This work mainly contains two parts with first part focusing on growing and characterizing high quality baseline solar cells and solar modules and second part concentrating on further reducing the material costs by growing thinner absorber layer with high efficiency.
The most difficult part in growing high quality CIGS solar cells originate from the absorber layers which contain p-type chalcopyrite structures with four different elements: Cu, In, Ga and Se. The widely used three-stage process is employed to co-evaporate In, Ga and Se first, then Cu and Se are evaporated to form the chalcopyrite CIGS structure and additional In, Ga and Se are deposited in the end to ensure an overall Cu deficiency, which is important for getting p-type semiconductors. The substrate temperatures during these three stages are carefully adjusted to introduce proper gallium gradients which is important for collecting electrons efficiently. Together with optimizing other layers we are able to get cell efficiency (area around 0.5 cm²) over 17%. To produce CIGS mini-modules, laser scribing as well as mechanical scribing are employed for series interconnection of individual cells using monolithic integration. The power and speed of laser together with the condition of mechanical scriber are carefully adjusted to ensure a minimum dead area in the module. Module (area around 80 cm²) with efficiency over 12% is produced.
Solar cells were fabricated and tested under varied temperature and weak light conditions. Temperature coefficient is compared between CIGS solar cells and other types of solar cells. Temperature coefficient is improved a lot with higher gallium content in the absorber layer. Weak light performance is shown to be increased a lot when copper percentage is lowered down. In order to examine the origin of beneficial effects from Cu-poor absorber, solar cells are grown with comparable grain sizes using our technique and I-V performances are examined under STM in grain/atomic scale. Leakage current is found to be mainly originates from boundary area. CIGS solar cells with Cu-poor absorber benefit from the reduced leakage from boundary area.
CIGS solar cells with thinner absorber thickness are studied and compared with conventional CIGS solar cells. We have found that high conversion efficiency solar cells can be grown for absorber thickness as thin as 1.5μm. Further reduction in absorber thickness deteriorates solar cell performances in both V∝ and Jsc resulting in conversion efficiency as low as 11%.
Two major approaches are performed to improve solar cell performances. Light trapping by etching AZO top contact for creating pyramid-structures to enhance light scattering. Efficiency is increased by more than 1.5% for solar cells with etched AZO surfaces. Solar cells with efficiency larger than 13% can be grown by using AZO etching. Another approach is by using suitable Ga content in absorber layer. Solar cells with efficiency as high as 14.17% are grown which makes thinner CIGS solar cells very competitive.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Yang, Shihang = 高效率、低成本銅銦鎵硒薄膜太陽能電池的製造 / 楊世航.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references (leaves 101-109).
Abstract also in Chinese.
Yang, Shihang = Gao xiao lu, di cheng ben tong yin jia xi bo mo tai yang neng dian chi de zhi zao / Yang Shihang.
Chapter 1 --- Introduction to Photovoltaics --- p.1
Chapter 1.1 --- Energy crisis --- p.1
Chapter 1.2 --- Physics of solar cells --- p.4
Chapter 1.2.1 --- Light Absorption --- p.4
Chapter 1.2.2 --- Charge Carrier Separation --- p.8
Chapter 1.2.3 --- Solar Cell I-V Characteristics --- p.9
Chapter 1.3 --- Classifications of Solar Cells --- p.11
Chapter 1.3.1 --- Crystalline silicon solar cell --- p.11
Chapter 1.3.2 --- Thin film solar cells --- p.12
Chapter 1.3.3 --- Organic and polymer solar cells --- p.13
Chapter 1.4 --- Cu(In,Ga)Se₂ (CIGS) based Solar Cells --- p.13
Chapter 1.4.1 --- State of the art --- p.13
Chapter 1.4.2 --- Material properties and structures --- p.14
Chapter 1.4.3 --- CIGS advantages --- p.17
Chapter 2 --- Integrated CIGS deposition system and fabrication process optimization --- p.21
Chapter 2.1 --- Introduction to vacuum deposition system --- p.21
Chapter 2.1.1 --- Integrated CIGS solar cell deposition system --- p.21
Chapter 2.1.2 --- Ni-Al top grid evaporation system --- p.23
Chapter 2.2 --- Fabrication processes --- p.23
Chapter 2.2.1 --- Substrate treatment --- p.23
Chapter 2.2.2 --- Molybdenum back contact deposition --- p.24
Chapter 2.2.3 --- CIGS absorber layer formation --- p.26
Chapter 2.2.4 --- Hetero-junction formation --- p.31
Chapter 2.2.5 --- Window layer optimization --- p.32
Chapter 2.2.6 --- Laser and mechanical scribing for mini-modules fabrication --- p.37
Chapter 2.3 --- Equipment improvements --- p.42
Chapter 2.3.1 --- Heating uniformity of substrate --- p.42
Chapter 2.3.2 --- Use of pyrometer for improved control of absorber thickness/composition --- p.43
Chapter 2.3.3 --- Se cracking unit --- p.45
Chapter 2.4 --- Characterization of CIGS solar cells --- p.47
Chapter 2.4.1 --- Morphology, composition and crystallinity --- p.47
Chapter 2.4.2 --- Depth profile of CIGS --- p.49
Chapter 2.4.3 --- Electrical property measurements --- p.51
Chapter 2.5 --- Conclusion --- p.54
Chapter 3 --- Performance of CIGS solar cells under non-standard test conditions --- p.56
Chapter 3.1 --- Temperature coefficient measurement of CIGS --- p.57
Chapter 3.1.1 --- Equipment set-up --- p.57
Chapter 3.1.2 --- Temperature coefficients for different types of solar cells . --- p.60
Chapter 3.1.3 --- CIGS solar cells with varied Ga/III composition --- p.65
Chapter 3.2 --- Weak Light Performance of CIGS --- p.69
Chapter 3.2.1 --- Introduction --- p.69
Chapter 3.2.2 --- Experiment --- p.72
Chapter 3.2.3 --- Results and discussion --- p.73
Chapter 3.3 --- Conclusion --- p.81
Chapter 4 --- CIGS solar cells with lower fabrication cost --- p.83
Chapter 4.1 --- Fabrication cost analysis for commercial CIGS solar cells --- p.83
Chapter 4.2 --- Thinner CIGS absorber layer --- p.84
Chapter 4.2.1 --- Solar cell performances with different absorber thicknesses --- p.84
Chapter 4.2.2 --- Performance improvement for thinner solar cell --- p.87
Chapter 4.3 --- Conclusion --- p.96
Chapter 5 --- Conclusion --- p.98
Chapter 5.1 --- Summary of previous researches --- p.98
Chapter 5.2 --- Future work --- p.99
Bibliography --- p.101
43
Davis, Jonathan Tesner. "Membraneless Electrolyzers for Solar Fuels Production". Thesis, 2019. https://doi.org/10.7916/d8-ypyq-6d71.
Testo completoAbstract (sommario):
Solar energy has the potential to meet all of society’s energy demands, but challenges remain in storing it for times when the sun is not shining. Electrolysis is a promising means of energy storage which applies solar-derived electricity to drive the production of chemical fuels. These so-called solar fuels, such as hydrogen gas produced from water electrolysis, can be fed back to the grid for electricity generation or used directly as a fuel in the transportation sector. Solar fuels can be generated by coupling a photovoltaic (PV) cell to an electrolyzer, or by directly converting light to chemical energy using a photoelectrochemical cell (PEC). Presently, both PV-electrolyzers and PECs have prohibitively high capital costs which prevent them from generating hydrogen at competitive prices. This dissertation explores the design of membraneless electrolyzers and PECs in order to simplify their design and decrease their overall capital costs.
A membraneless water electrolyzer can operate with as few as three components: A cathode for the hydrogen evolution reaction, an anode for the oxygen evolution reaction, and a chassis for managing the flows of a liquid electrolyte and the product gas streams. Absent from this device is an ionically conducting membrane, a key component in a conventional polymer electrolyte membrane (PEM) electrolyzer that typically serves as a physical barrier for separating product gases generated at the anode and cathode. These membranes can allow for compact and efficient electrolyzer designs, but are prone to degradation and failure if exposed to impurities in the electrolyte. A membraneless electrolyzer has the opportunity to reduce capital costs and operate in non-pristine environments, but little is known about the performance limitations and design rules that govern operation of membraneless electrolyzers. These design rules require a thorough understanding of the thermodynamics, kinetics, and transport processes in electrochemical systems. In Chapter 2, these concepts are reviewed and a framework is provided to guide the continuum scale modeling of the performance of membraneless electrochemical cells. Afterwards, three different studies are presented which combine experiment and theory to demonstrate the mechanisms of product transport and efficiency loss.
Chapter 3 investigates the dynamics of hydrogen bubbles during operation of a membraneless electrolyzer, which can strongly affect the product purity of the collected hydrogen. High-speed video imaging was implemented to quantify the size and position of hydrogen gas bubbles as they detach from porous mesh electrodes. The total hydrogen detected was compared to the theoretical value predicted by Faraday’s law. This analysis confirmed that not all electrochemically generated hydrogen enters the gas phase at the cathode surface. In fact, significant quantities of hydrogen remain dissolved in solution, and can result in lower product collection efficiencies. Differences in bubble volume fraction evolved along the length of the cathode reflect differences in the local current densities, and were found to be in agreement with the primary current distribution. Overall, this study demonstrates the ability to use in-situ HSV to quantitatively evaluate key performance metrics of membraneless electrolyzers in a non-invasive manner. This technique can be of great value for future experiments, where statistical analysis of bubble sizes and positions can provide information on how to collect hydrogen at maximum purity.
Chapter 4 presents an electrode design where selective placement of the electrocatalyst is shown to enhance the purity of hydrogen collected. These “asymmetric electrodes” were prepared by coating only one planar face of a porous titanium mesh electrode with platinum electrocatalyst. For an opposing pair of electrodes, the platinum coated surface faces outwards such that the electrochemically generated bubbles nucleate and grow on the outside while ions conduct through the void spacing in the mesh and across the inter-electrode gap. A key metric used in evaluating the performance of membraneless electrolyzers is the hydrogen cross-over percentage, which is defined as the fraction of electrochemically generated hydrogen that is collected in the headspace over the oxygen-evolving anode. When compared to the performance of symmetric electrodes – electrodes coated on both faces with platinum – the asymmetric electrodes demonstrated significantly lower rates of cross-over. With optimization, asymmetric electrodes were able to achieve hydrogen cross-over values as low as 1%. These electrodes were then incorporated into a floating photovoltaic electrolysis device for a direct demonstration of solar driven electrolysis. The assembled “solar fuels rig” was allowed to float in a reservoir of 0.5 M sulfuric acid under a light source calibrated to simulate sunlight, and a solar to hydrogen efficiency of 5.3% was observed.
In Chapter 5, the design principles for membraneless electrolyzers were applied to a photoelectrochemical (PEC) cell. Whereas an electrolyzer is externally powered by electricity, a PEC cell can directly harvest light to drive an electrochemical reaction. The PEC reactor was based on a parallel plate design, where the current was demonstrated to be limited by the intensity of light and the concentration of the electrolyte. By increasing the average flow rate of the electrolyte, mass transport limitations could be alleviated. The limiting current density was compared to theoretical values based off of the solution to a convection-diffusion problem. This modeled solution was used to predict the limitations to PEC performance in scaled up designs, where solar concentration mirrors could increase the total current density. The mass transport limitations of a PEC flow cell are also highly relevant to the study of CO2 reduction, where the solubility limit of CO2 in aqueous electrolyte can also limit performance.
44
I-LANG, TSAI, e 蔡一郎. "Amorphous Silicon thin film Solar Cells by Laser Annealing and Ion Implantation Low Temperate Process Design on Glass". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/79363614942100591800.
Testo completoAbstract (sommario):
碩士中華大學
機械與航太工程研究所
95
The purpose of this paper is for the amorphous silicon solar cell design and performance analyses on the low sodium glass substrate. The electric conductive and characteristics analyses were tested for the P/N junction, aluminum electrode as well as the transparent ITO layer. The thin film layers of P/N junction, aluminum electrode as well as the transparent ITO were obtained by ion implantation, E-gun evaporation and Plasma Enhanced Chemical Vapor Deposition (PECVD) methods, respectively. In order to raise the performance efficiency of solar cell on the glass substrate, each layer was annealed by 532nm CO2 laser for re-crystallization. The fabrication processes on the low sodium glass were developed, although the efficiency is still too low. We are looking forwards to get both of the material and the process to be the best collocation onto promotion of the electricity of the solar cell to the commercialized scale in the near future.
45
Cheng, Felice, e 鄭淑珍. "The Design of Low Power Implantable Pseudo-BJT-Based Silicon Retina with Solar Cells for Artificial Retinal Prostheses". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/n4n2xv.
Testo completoAbstract (sommario):
碩士國立交通大學
電子工程系所
92
In this thesis, the Pseudo-BJT-based silicon retina with solar cells for artificial retinal prosthesis is designed and fabricated in 0.35um CMOS technology. The Pseudo-BJT-based silicon retina possesses more functions of retinal cells than current sub-retinal prosthesis. Besides, the solar cell is used to supply power to the artificial retina and this feature makes implantation of the chip to the eye more feasible. Two artificial retinal prostheses are fabricated with a standard TSMC 0.35um CMOS process: one is for implantation and the other is for instrument measurement, which is measured completely. The chip is demonstrated to have the functions of the retinal cells: photoreceptors, horizontal cells and bipolar cells. The measured voltage of the on-chip power supply, solar cell, is at least 0.7 volt under illumination of 2010 lux. The functions of the artificial retina have been demonstrated to be correct with solar cells as power supply.
46
Bahabry, Rabab R. "Towards Cost-Effective Crystalline Silicon Based Flexible Solar Cells: Integration Strategy by Rational Design of Materials, Process, and Devices". Diss., 2017. http://hdl.handle.net/10754/626350.
Testo completoAbstract (sommario):
The solar cells market has an annual growth of more than 30 percent over the past 15 years. At the same time, the cost of the solar modules diminished to meet both of the rapid global demand and the technological improvements. In particular for the crystalline silicon solar cells, the workhorse of this technology. The objective of this doctoral thesis is enhancing the efficiency of c-Si solar cells while exploring the cost reduction via innovative techniques. Contact metallization and ultra-flexible wafer based c-Si solar cells are the main areas under investigation.
First, Silicon-based solar cells typically utilize screen printed Silver (Ag) metal contacts which affect the optimal electrical performance. To date, metal silicide-based ohmic contacts are occasionally used for the front contact grid lines. In this work, investigation of the microstructure and the electrical characteristics of nickel monosilicide (NiSi) ohmic contacts on the rear side of c-Si solar cells has been carried out. Significant enhancement in the fill factor leading to increasing the total power conversion efficiency is observed.
Second, advanced classes of modern application require a new generation of versatile solar cells showcasing extreme mechanical resilience. However, silicon is a brittle material with a fracture strains <1%. Highly flexible Si-based solar cells are available in the form thin films which seem to be disadvantageous over thick Si solar cells due to the reduction of the optical absorption with less active Si material. Here, a complementary metal oxide semiconductor (CMOS) technology based integration strategy is designed where corrugation architecture to enable an ultra-flexible solar cell module from bulk mono-crystalline silicon solar wafer with 17% efficiency. This periodic corrugated array benefits from an interchangeable solar cell segmentation scheme which preserves the active silicon thickness and achieves flexibility via interdigitated back contacts. These cells can reversibly withstand high mechanical stress as the screen-printed metals have fracture strain >15%. Furthermore, the integration of the cells is demonstrated on curved surfaces for a fully functional system.
Finally, the developed flexing approach is used to fabricate three-dimensional dome-shaped cells to reduce the optical coupling losses without the use of the expensive solar tracking/tilting systems.
47
Chen, Chien-Wei, e 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.
Testo completoAbstract (sommario):
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.
48
Mayer, Alexander Rui Pfaff. "Development and construction of a device related to a new structured metallization concept for back-contact crystalline silicon solar cells by using metal foil". Master's thesis, 2014. http://hdl.handle.net/10316/38835.
Testo completoAbstract (sommario):
Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia da Universidade de CoimbraMetallization and contacting processes have a significant impact on the total manufacturing cost of the high-efficiency solar cells. The metallization of silicon crystalline back-contact solar cells is difficult and still a major issue from the industrial point of view. The core of the current thesis introduces the development of a device, designed to realize and evaluate the potential of a new rear side metallization concept for backcontact cells. Here, the formation of the electrode pattern is based on contacting and structuring a metal foil through a laser processing scheme. In order to ensure a good metallic contact, the developed device shall first assure a safe foil fixing and later an appropriate handling for structuring the metal foil in order to make selective metallic contacts. Meanwhile, the major technological challenges faced during the device development are identified and assessed. Finally this device has been developed and tested at the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, Germany An overall conclusion of the experimental findings has been made and an outlook for further investigations required in this field has been proposed at the end of this document.
Os processos de fabrico referentes à metalização em células solares de alta eficiência têm um elevado impacto no seu custo global de manufatura. Em particular a metalização de células em silício cristalino do tipo Back-Contact mostra-se ser difícil e, desta forma, um problema do ponto de vista industrial. Este trabalho de tese trata do desenvolvimento de um dispositivo projetado para realizar e avaliar o potencial de um novo conceito de metalização destinado à face traseira de células do tipo Back-Contact. Aqui, a formação dos eletródios em padrão, baseia-se em contactar e estruturar uma folha de alumínio através de aplicação a laser. De forma a garantir um bom contacto metálico, o dispositivo desenvolvido deverá primeiramente assegurar uma boa fixação da folha de alumínio com o substrato, assim como um bom desempenho para a posterior estruturação da folha. Desta forma serão criados os contactos metálicos seletivos. Entretanto, os principais desafios tecnológicos enfrentados durante o desenvolvimento do dispositivo serão identificados e corrigidos. Este aparelho foi desenvolvido e testado no Fraunhofer Instituto de Sistema Energéticos Solares ISE em Friburgo, Alemanha. Por fim, foram ainda efetuados ensaios com o dispositivo, tirando-se as primeiras conclusões acerca do desempenho deste novo conceito de metalização. Serão apresentadas algumas sugestões para futuras investigações nesta área.
49
Altschul, Emmeline Beth. "Transition metal solar absorbers". Thesis, 2012. http://hdl.handle.net/1957/33382.
Testo completoAbstract (sommario):
A new approach to the discovery of high absorbing semiconductors for solar cells was taken by working under a set of design principles and taking a systemic methodology. Three transition metal chalcogenides at varying states of development were evaluated within this framework. Iron pyrite (FeS���) is well known to demonstrate excellent absorption, but the coexistence with metallic iron sulfides was found to disrupt its semiconducting properties. Manganese diselenide (MnSe���), a material heavily researched for its magnetic properties, is proposed as a high absorbing alternative to iron pyrite that lacks destructive impurity phases. For the first time, a MnSe��� thin film was synthesized and the optical properties were characterized. Finally, CuTaS���, a known but never characterized material, is also proposed as a high absorbing semiconductor based on the design principles and experimental results.Graduation date: 2013
50
Ghane, Parvin. "Fabrication and analysis of CIGS nanoparticle-based thin film solar cells". 2013. http://hdl.handle.net/1805/3697.
Testo completoAbstract (sommario):
Indiana University-Purdue University Indianapolis (IUPUI)Fabrication and analysis of Copper Indium Gallium di-Selenide (CIGS) nanoparticles-based thin film solar cells are presented and discussed. This work explores non-traditional fabrication processes, such as spray-coating for the low-cost and highly-scalable production of CIGS-based solar cells. CIGS nanoparticles were synthesized and analyzed, thin CIGS films were spray-deposited using nanoparticle inks, and resulting films were used in low-cost fabrication of a set of CIGS solar cell devices. This synthesis method utilizes a chemical colloidal process resulting in the formation of nanoparticles with tunable band gap and size. Based on theoretical and experimental studies, 100 nm nanoparticles with an associated band gap of 1.33 eV were selected to achieve the desired film characteristics and device performances. Scanning electron microcopy (SEM) and size measurement instruments (Zetasizer) were used to study the size and shape of the nanoparticles. Electron dispersive spectroscopy (EDS) results confirmed the presence of the four elements, Copper (Cu), Indium (In), Gallium (Ga), and Selenium (Se) in the synthesized nanoparticles, while X-ray diffraction (XRD) results confirmed the tetragonal chalcopyrite crystal structure. The ultraviolet-visible-near infra-red (UV-Vis-NIR) spectrophotometry results of the nanoparticles depicted light absorbance characteristics with good overlap against the solar irradiance spectrum. The depositions of the nanoparticles were performed using spray-coating techniques. Nanoparticle ink dispersed in ethanol was sprayed using a simple airbrush tool. The thicknesses of the deposited films were controlled through variations in the deposition steps, substrate to spray-nozzle distance, size of the nozzle, and air pressure. Surface features and topology of the spray-deposited films were analyzed using atomic force microscopy (AFM). The deposited films were observed to be relatively uniform with a minimum thickness of 400 nm. Post-annealing of the films at various temperatures was studied for the photoelectric performance of the deposited films. Current density and voltage (J/V) characteristics were measured under light illumination after annealing at different temperatures. It was observed that the highest photoelectric effect resulted in annealing temperatures of 150-250 degree centigrade under air atmosphere. The developed CIGS films were implemented in solar cell devices that included Cadmium Sulfide (CdS) and Zinc Oxide (ZnO) layers. The CdS film served as the n-type layer to form a pn junction with the p-type CIGS layer. In a typical device, a 300 nm CdS layer was deposited through chemical bath deposition on a 1 $mu$m thick CIGS film. A thin layer of intrinsic ZnO was spray coated on the CdS film to prevent shorting with the top conductor layer, 1.5 μm spray-deposited aluminum doped ZnO layer. A set of fabricated devices were tested using a Keithley semiconductor characterization instrument and micromanipulator probe station. The highest measured device efficiency was 1.49%. The considered solar cell devices were simulated in ADEPT 2.0 solar cell simulator based on the given fabrication and experimental parameters. The simulation module developed was successfully calibrated with the experimental results. This module can be used for future development of the given work.