Dissertationen zum Thema „MAPbCl3“

The presented diploma thesis deals with the preparation of perovskite single crystals by inverse thermal crystallization and subsequent study of the basic properties of these hybrid organic-inorganic materials that can be used in various optoelectronic (photodetectors, transistors, lasers, LEDs) or photovoltaic applications. Their behavior in the electric field was studied by impedance spectroscopy. Impedance and capacitance-voltage (C-V) characteristics (frequency dependences) were measured in the dark and in the light. From the impedance dependences for measurements at 0 V voltage in the dark, the equivalent circuit was modeled and its parameters and dielectric constant were determined. From the C-V dependence, Mott-Schottky analysis determined the parameters – "flat-band" potential U_"fb" and charge carrier density N_"C-V" , the parameter – the so-called Warburg coefficient was found, which together with the parameter N_"C-V" was used to calculate the diffusion coefficient D.

This diploma thesis is focused on preparation of perovskite methylammonium lead bromide thin film layers and also thin film layers of its precursors, namely methylammonium bromide and lead(II) bromide, by spin-coating from the solution; and optical characterisation of the prepared thin film layers by UV-VIS spectroscopy and spectroscopical ellipsometry. Methylammonium bromide does not absorb in visible nor ultraviolet region, the maximum absorption of lead(II) bromide occurred in ultraviolet region, methylammonium lead bromide absorbs in visible region. Optical band gaps were determined by Tauc method to (3,5 ± 0,1) eV for lead(II) bromide and 2,15 eV, respectively 2,25 eV for perovskite. Refractive indices and extinction coefficients were determined by ellipsometry in range of wavelengths from 290 nm to 830 nm and their dependence with layer thickness was discussed. Ellipsometry model used in this thesis consist on Tauc-Lorentz oscillators for methylammonium bromide, methylammonium lead bromide and partially for lead(II) bromide, which another part is formed by New Amorphous oscillator.

This thesis is focused on the study of the detection of electromagnetic radiation using monocrystalline perovskites. Theoretical part deals with basic principles of detections and possible applications of hybrid perovskite crystals in the field of ultraviolet and visible spectrum detection. Parameters of the recently published perovskite photodetectors are also presented. Experimental part describes synthesis, structural and optical properties of MAPbBr3 single crystals and electrical characterization of the Au/MAPbBr3/Au photodetector. Photodetector parameters (responsivity, external quantum efficiency and specific detectivity) are calculated based on the spectral and switching (on/off) current responses.

Negli ultimi anni i dispositivi optoelettronici basati su perovskiti ibride ad alogenuri organo-metallici, come celle solari e rivelatori di radiazione, hanno destato un crescente interesse per le loro straordinarie performance. Nonostante questo, molte proprietà fondamentali di questi materiali sono ancora sconosciute e il loro studio è la chiave per l’ottimizzazione dei dispositivi finali. Per realizzare questo lavoro di tesi sono state eseguite misure di fotoluminescenza (PL) su cristalli singoli di tribromuro di metilammonio di piombo (MAPbBr3) a seguito di irradiamento con raggi X, con l’obiettivo di comprendere l’effetto della radiazione sulla struttura elettronica del materiale. In particolare, lo studio dei campioni è finalizzato ad analizzare il comportamento degli eccitoni, la principale sorgente di fotoluminescenza in questi materiali. Si è scelto di eseguire misure di PL per confermare l’ipotesi, nata da misure precedenti di assorbimento in funzione dell’irraggiamento effettuate dal gruppo di ricerca, che l’irraggiamento modifichi l’energia di legame eccitonica nel materiale. I dati risultanti dagli spettri di PL hanno fornito informazioni in accordo con tale ipotesi, rivelandosi uno strumento efficace per analizzare e comprendere le proprietà ottiche di questi materiali.

Les perovskita orgàniques/inorgàniques híbrides han atret molta atenció des que es van introduir per primera vegada en un dispositiu fotovoltaic fa deu anys, obtenint una eficiència de el 3%. Des de llavors, l’eficiència de les cel·les solars de perovskita ha augmentat fins a gairebé igualar l’eficiència de les cel·les fotovoltaiques comercials de silici. A més, permet la fabricació de dispositius flexibles a un preu reduït. A causa de les seves propietats optoelectròniques excepcionalment bones, també s’està duent a terme una intensa recerca per trobar diferents aplicacions d’aquest tipus de materials, ja sigui com a sensors, làsers o díodes emissors de llum. No obstant això, encara s’han d’abordar alguns problemes que presenten, com la inestabilitat química o estructural en condicions ambientals. Per tal de comprendre millor l’estabilitat estructural i el paper exercit per la interacció entre el catió orgànic i la xarxa inorgànica, estudiem les propietats estructurals i optoelectròniques de les perovskita de la família FAxMA1-xPbI3 a diferents pressions (fins a 15 GPa) i temperatures (de 10 a 385 K). La nostra investigació d’aquest material és realitzada per mitjà d’espectroscòpia òptica no invasiva, com fotoluminiscència (PL), Raman i elipsometría. En els articles aquí recopilats es mostra el primer diagrama de fase complet de perovskita de iodur de plom de cations mixtes (formamidinio i metilamonio), en funció de la temperatura i la composició. Aquest diagrama pot servir per avaluar la concentració relativa òptima dels cations orgànics per estabilitzar la fase cúbica pel que fa als canvis de temperatura. Aquests materials també presenten una dependència atípica del bandgap amb temperatura, que en la literatura s’atribueix exclusivament a la renormalització del gap causa de la interacció electró-fonó. No obstant això, és aquest treball mostrem que els efectes d’expansió tèrmica també juguen un paper decisiu en la dependència del gap amb temperatura. De totes les combinacions de la família de perovskita d’halur organometàl·lic, MAPbI3 és probablement el més estudiat a causa de les seves excel·lents propietats. Se sap que la interacció entre el moviment dels cations orgànics i la gàbia inorgànica rígida té un paper decisiu en l’estructura cristal·lina d’aquest material. Per exemple, a causa de el desordre dinàmic de les molècules de metilamonio, la perovskita MAPbI3 adopta una fase cúbica altament simètrica a altes temperatures. Quan es refreda, tant la contracció de la xarxa com la reducció de la simetria a causa d’una transició a una fase ortorrómbica bloquegen les molècules de MA en els buits de la xarxa inorgànica. En els articles aquí compilats observem per primera vegada un efecte similar però a temperatura ambient, aplicant pressió hidrostàtica a el material. En ambdós casos, el bloqueig dels cations de MA es pot observar indirectament a través d’una reducció dràstica dels amples de línia de fonons en els mesuraments Raman. Demostrant, d’aquesta manera, que és possible alterar les propietats vibratòries del material aplicant una pressió controlada. Finalment, la modificació del valor del bandgap i la variació de l’estructura de bandes de sistema mixt FAxMA1-xPbI3 s’avalua en funció de la composició de FA amb elipsometría i fotoluminiscència.
Las perovskitas orgánicas/inorgánicas híbridas han atraído mucha atención desde que se introdujeron por primera vez en un dispositivo fotovoltaico hace diez años, obteniendo una eficiencia de alrededor del 3%. Desde entonces, la eficiencia de las celdas solares de perovskita ha aumentado hasta casi igualar la eficiencia de las celdas fotovoltaicas comerciales de silicio. Además, permite la fabricación de dispositivos flexibles a un precio reducido. Debido a sus propiedades optoelectrónicas excepcionalmente buenas, también se está llevando a cabo una intensa investigación para encontrar diferentes aplicaciones de este tipo de materiales, ya sea como sensores, láseres o diodos emisores de luz. Sin embargo, todavía deben abordarse algunos problemas que presentan, como la inestabilidad química o estructural en condiciones ambientales. Con el fin de comprender mejor la estabilidad estructural y el papel desempeñado por la interacción entre el catión orgánico y la red inorgánica, estudiamos las propiedades estructurales y optoelectrónicas de las perovskitas de la familia FAxMA1-xPbI3 a diferentes presiones (hasta 15 GPa) y temperaturas (de 10 a 385 K). Nuestra investigación de este material es realizada por medio de espectroscopía óptica no invasiva, como fotoluminiscencia (PL), Raman y elipsometría. En los artículos aquí recopilados se muestra el primer diagrama de fase completo de perovskitas de yoduro de plomo de cationes mixtos (formamidinio y metilamonio), en función de la temperatura y la composición. Este diagrama puede servir para evaluar la concentración relativa óptima de los cationes orgánicos para estabilizar la fase cúbica con respecto a los cambios de temperatura. Estos materiales también presentan una dependencia atípica del bandgap con temperatura, que en la literatura se atribuye exclusivamente a la renormalización del gap debido a la interacción electrón-fonón. Sin embargo, es éste trabajo mostramos que los efectos de expansión térmica también juegan un papel decisivo en la dependencia del gap con temperatura. De todas las combinaciones de la familia de perovskitas de haluro organometálico, MAPbI3 es probablemente el más estudiado debido a sus excelentes propiedades. Se sabe que la interacción entre el movimiento de los cationes orgánicos y la jaula inorgánica rígida tiene un papel decisivo en la estructura cristalina de este material. Por ejemplo, debido al desorden dinámico de las moléculas de metilamonio, la perovskita MAPbI3 adopta una fase cúbica altamente simétrica a altas temperaturas. Cuando se enfría, tanto la contracción de la red como la reducción de la simetría debido a una transición a una fase ortorrómbica bloquean las moléculas de MA en los huecos de la red inorgánica. En los artículos aquí compilados observamos por primera vez un efecto similar pero a temperatura ambiente, aplicando presión hidrostática al material. En ambos casos, el bloqueo de los cationes de MA se puede observar indirectamente a través de una reducción drástica de los anchos de línea de fonones en las mediciones Raman. Demostrando, de ésta manera, que es posible alterar las propiedades vibratorias del material aplicando una presión controlada. Finalmente, la modificación del valor del bandgap y la variación de la estructura de bandas del sistema mixto FAxMA1-xPbI3 se evalúa en función de la composición de FA con elipsometría y fotoluminiscencia.
Hybrid organic/inorganic perovskites have attracted a lot of attention since they were first introduced in a working photovoltaic device ten years ago, yielding an efficiency of around 3%. Since then, the efficiency of the perovskite solar cells has risen to almost stand toe to toe with that of commercial silicon photovoltaics. Besides, it allows the fabrication of flexible devices at an inexpensive cost. Due to its exceptionally good optoelectronic properties, there is also an intense research for different applications of this type of materials, such as sensors, lasers or light-emitting diodes. However, they still present some issues that need to be addressed, such as chemical or structural instabilities under ambient conditions. In order to better understand the structural stability, and the role played by the interaction between the organic cation and the inorganic framework, we studied the structural and optoelectronic properties of perovskites of the family FAxMA1-xPbI3 at different pressures (up to 15 GPa) and temperatures (10 to 385 K). We investigated this material by noninvasive optical spectroscopy means, such as photoluminescence (PL), Raman and ellipsometry. In the articles here compiled, the first complete phase diagram of mixed cation (formamidinium and methylammonium) lead iodide perovskites is provided as a function of temperature and composition. This serves to assess the best relative concentration of the organic cations to stabilize the cubic phase with respect to temperature changes. These materials also present an atypical dependence of the bandgap with temperature, which in the literature is ascribed exclusively to a huge electron-phonon renormalization. However, here we show that thermal expansion effects also play a decisive role in the temperature behavior of the fundamental gap. From all the combinations in the family of organometal halide perovskites, MAPbI3 is probably the most studied due to its outstanding optoelectronic properties. It is known that the interplay between the movement of the organic cations and the rigid inorganic cage has a decisive role in the crystalline structure of this material. For instance, due to the dynamic disorder of the methylammonia, MAPbI3 adopts a highly symmetric cubic phase at high temperatures. When cooling down, both the contraction of the lattice and the reduction of symmetry due to a transition to an orthorhombic phase lock the MA molecules in the cage voids. We are able to observe for the first time a similar effect but at room temperature, by applying hydrostatic pressure to the material. In both cases, the locking of the MA cations can be indirectly observed through a drastic reduction of the phonon linewidths in Raman experiments. We have shown, in this way, that it is possible to alter the vibrational properties of the material by applying a controlled hydrostatic pressure. Finally, the tuning of the bandgap and the variation of the band structure of the mixed-system FAxMA1-xPbI3 is evaluated as a function of FA composition with ellipsometry and photoluminescence.

碩士
國立臺北科技大學
光電工程系
106
In this study, MAPbBr3 perovskite quantum dots (QD-MAPbBr3) were prepared by as simple and rapid method.Octylammonium bromide (OABr) makes MAPbBr3 with better exciton binding energy, surface morphology and stability.Moreover,the color of the MAPbBr3 film is dark orange,but it becomes light yellow after OABr used.Therefore MAPbBr3 added with OABr have a better light transmittance.To form a nanocrystalline thin film,QD-MAPbBr3 was coated on NiO or PEDOT:PSS thin films grown on patterned ITO substrates by a spin-coating method in a nitrogen-filled glove box for devices.Subsequently, C60 and Ag were deposited on QD-MAPbBr3 films using a thermal evaporation to fabricate Glass/ITO/NiO/QD-MAPbBr3/C60/Ag perovskite solar cells,where NiO, QD-MAPbBr3, C60 were used as a hole transport layer,active layer and electron transport layer,respectively.To realize material characteristics,x-ray diffraction (XRD),scanning electron microscope (SEM),UV/VIS/NIR spectrometer,and photoluminescence spectrometers (PL) were used to analysis crystallinity,surface morphology,transmittance,and optical behavior of the QD-MAPbBr3 films.The J-V characteristics of devices were evaluated by a solar simulator system.

碩士
國立臺北科技大學
光電工程系
107
This thesis is on metal-semiconductor-metal MAPbBr3 perovskite crystal photodetector. Perovskite crystals are produced by constant temperature growth. To explore the effect of different crystal growth temperature on crystal structure, we analyzed the crystal structure, crystal uniformity, and defects by XRD and PL. We found the best temperature for crystal growth and subsequently fabricated the perovskite crystal into photodetector. The current-to-voltage characteristic curve（IV curve）, optical responsivity, and carrier mobility of the light detector were measured. The electrode of the photodetector is an interdigitated structure in which MAPbBr3 perovskite crystal semiconductor materials are used as a light absorbing layer. On the electrode, C60 is used as an electron transport layer, resulting in a light response exhibited at an incident light wavelength of 400 nm. When the photodetector was biased to 15V, 16V, 17V, 18V, 19V and 20V, the optimal optical responsivity is 13.13 A/W, 14.97 A/W, 17.13 A/W, 19.98 A/W, 22.48 A/W and 24.50 A/W; the carrier mobility was 14.4 cm2V-1s-1.

碩士
國立臺北科技大學
分子科學與工程系有機高分子碩士班
106
Perovskite solar cells have attracted great attention due to their advantages of low cost manufacturing, solvent process, high power conversion efficiency and potential to replace silicon solar cells. The solvent deposition method for perovskite coating is generally categorized into one-step and two-step sequential deposition processes. Compared with the two-step deposition process, the one-step solution deposition method is quite simple, cost-effective and requires shorter time. However, one-step solution processed perovskite films generally exhibit inhomogeneous surface morphology, irregular crystallinity, and poor reproducibility. To improve the film quality, it often requires the introduction of anti-solvent to clean the extra coordination additives during film growth via one-step process. However, the cleaning time is plays a critical role in determining the proveskite crystal growth and reproducibility of device performances. In this study, we used P3HT-COOH as an HTM (instead of PEDOT:PSS) and Sulfolane as a solvent additive (instead of DMSO) and investigated the effect of anti-solvent ether washing delay time on the proveskite film formation and their photovoltaic performance in an inverted device configuration of ITO/P3HT-COOH/Proveskite/PC60BM/PEI/Ag. X-ray diffraction analysis suggests that proveskite film fabricated by using sulfolane additive skipped the formation of intermediate phase and form perovskite crystallinities directly. The PSCs device with DMF and sulfolane washed by ether at 30th s exhibit the PCE of 16.15±0.28%. Further increasing of washing delay time from 30th s to 90th s, the device exhibit stable PCE of 16.05±0.29%. In contrast, proveskite device with DMF and DMSO additive washed by ether at 30th s exhibits the PCE of 16.54±0.34%. Further increasing of washing delay time from 30th s to 90th s significantly worsens all of the photovoltaic parameters, yielding a very poor PCE of 0.15±0.10%. Further, large area (1 cm2) PSCs were fabricated with different anti-solvent engineering method such as drop casting, immersion and immersion with stirring . The average PCE observes as 12.70±0=1.15% for drop casting, 9.16±1.74% for immersion and 11.50±1.01% for immersion with method, respectively.

碩士
國立臺北科技大學
光電工程系
106
In this study,MAPbI3 was coated on ITO (Indium Tin Oxide) substrate with a PEDOT:PSS film to form a thin film in a nitrogen-filled glove box, followed by a layer of QD (FAPbBr1.5I1.5 , FAPbBrI2) thin film, followed by thermal evaporation of C60, Ag, and finally made into a perovskite solar cell of Glass / ITO/ PEDOT:PSS / MAPbI3/ QD-FAPbX3 /C60 / Ag, with PEDOT:PSS as a hole transmission layer, MAPbI3, QD as a light absorbing layer, and C60 acts as an electron transport layer. This paper is mainly to synthesize FAPbX3 Perovskite Quantum Dots (QD-FAPbBr1.5I1.5, FAPbBrI2) by a simple method to calculate the equivalent powder, and then dope n-octylamine, oleic acid to make QD better. The exciton binding energy, surface morphology and stability, the color part is brown-red, can get higher wavelength light after excitation. For the characteristic analysis of the components,using a field emission scanning electron microscope(SEM) to analysis morphology and the cross-sectional structure of the thin film, and the Ultraviolet/visible spectrophotometer analysis of its penetration, absorption spectrum, optical excitation light measurement system to analyze the optical properties, the component part is measured by a solar simulator to measure its J-V curve to obtain its open-circuit voltage (Voc), current density (Jsc), fill factor (FF), and photoelectric conversion efficiency (PCE).

碩士
國立臺北科技大學
光電工程系
106
In this study, perovskite solar cells were fabricated using highly conductive PEDOT:PSS as conductive material instead of traditional indium tin oxide (ITO). First, a conductive layer, a hole transport layer, and an active layer film are prepared by spin-coating, and then a C60 and silver electrode are formed by a thermal evaporation method. The structure is as follows: Glass/highly conductive PEDOT:PSS /PEDOT:PSS/CH3NH3PbI3/ C60/Ag. In this study, DMSO was used to stabilize the film stability of conductive film, and a flat MAPbI3 crystal film was formed on the PEDOT:PSS film by One-Step spin coating to realize the production of an organic perovskite solar cell. Field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and UV-VIS transmission spectroscopy were used to observe the optical properties such as surface morphology, crystallite size, crystal phase, and light transmission. We changed the thickness of the transparent conductive layer and the hole transport layer, discussed the differences of solar cells under different conditions, and measured the optical properties under different conditions to be inseparable from the perovskite solar cells. The J-V curve, open circuit voltage (VOC), short circuit current density (JSC), fill factor (F.F), and power conversion efficiency (PCE) of the solar cells.

碩士
國立清華大學
動力機械工程學系
105
This research starts with the computational quantum mechanics, using first principles to simulate the chlorine doping effect with different concentration (x value) on the optical and thermoelectric properties of 3D mixed halide methylammonium lead perovskites (MAPbI3-xClx). Finding the highest thermoelectric figure of merit (ZT) and suitable solar absorbance range are our major targets. The 3D bulk MAPbI3 is considered as a potential mineral semiconductor material for future solar cells and thermoelectric chips. It has good electrical properties, low thermal conductivity, and only needs low cost to produce. This research employed the Khon-Sham theory, PBE (Perdew–Burke–Ernzerhof) exchange correlation energy functional, and self-consistent field (SCF) method, to calculate the plane wave in the reciprocal space. In the electron simulation, we used the density functional theory (DFT) to evaluate the band structure and electron density of states to calculate the optical band gaps. Then applying Boltzmann transport equation (BTE) to calculate the electrical conductivity σ, carrier thermal conductivity κ_el, and Seebeck coefficient S. In the phonon simulation, we used density functional perturbation theory (DFPT) to evaluate the phonon dispersion relation and phonon density of states, and applied the Debye model to calculate the phonon thermal conductivity κ_ph. This research has found that the main contribution to the heat transfer is mainly from phonons, especially the optical parts, the contribution from electrons is little. In addition, doping Cl will increase not only electrical conductivity, but also phonon thermal conductivity. The latter is because of the production of soft modes and the reduction of averaged weight. At the very low Cl doping concentration, e.g. x=0.25, electrical conductivity increases while the thermal conductivity almost remain the same values as MAPbI3, ZT value rises up from 1.41×〖10〗^(-7) to 8.26×〖10〗^(-7). The latter is about 6 times greater than the former. Doping carriers, such as electrons or holes, ZT value can grow up to 10 times the value of MAPbI3, at the same carrier concentration condition. When electron or hole doping concentration reaches 〖10〗^20 cm^(-3), the ZT value of MAPbI3 would achieve 2.00×〖10〗^(-5) and 2.21×〖10〗^(-4) respectively, which is 1000 times the value of the intrinsic condition, and it’s 2.09×〖10〗^(-4) and 2.09×〖10〗^(-3) for condition x=0.25. In the study of the optical property, we obtained that the main absorbance wavelength located in the ultraviolet light region (40nm < λ < 400nm) and visible light region (400nm < λ < 700nm). MAPbI3-xClx has wider absorption range, but its absorption coefficient decreases with the Cl concentration. The design of the heat absorber of the solar thermoelectric chips must enhance the thermal radiation absorption in the range of λ ≥ 400 nm, which is the region from visible to infrared light. Finally, the conclusion of this research is that the MAPbI2.75Cl0.25 is the best tuning for the light absorption layer in the solar cell, and highest ZT value for the thermoelectric chip. Hence it can improve the performance of future solar thermoelectric chips.

碩士
國立中興大學
精密工程學系所
107
Hybrid organic-inorganic perovskite is the most promising solar cell material in recent years. In this thesis, the rutile phase of titanium dioxide with the nanorod structure is synthesized by the hydrothermal method. The influences of the microstructure of titanium dioxide on sequential deposited perovskites and their conversion efficiency are systemically investigated. This thesis can be basically divided into two parts. The first part of the thesis is mainly focused on the study of the reaction temperature, the reaction concentration and the reaction time during the hydrothermal synthesis. The scanning electron microscope (SEM) and X-ray diffractometer (XRD) were used to analyze the microstructure, surface morphology and crystalline structure of the as-synthesized titanium dioxide and understand the relationship between their properties and the hydrothermal processing parameters. The second part of the thesis is mainly focused on the effect of nanorod titanium dioxide with different lengths on the sequential deposited perovskites. In the experiment, the methylammonium lead iodide (CH3NH3PbI3) was selected and prepared by the sequential deposition on a series of nanorod titanium dioxides with different lengths and commonly used mesoporous titanium dioxide. The analyses of the microstructure, the crystallinity, the optical property of as-prepared perovskites were performed to investigate the relationship between the sequential deposited perovskites and different titanium dioxides. Our experimental result shows that the perovskite solar cell using nanorod titanium dioxide can exhibit a conversion efficiency of 13% because of the better transition of lead iodide to perovskite and the improved carrier collection.

碩士
國立臺北科技大學
光電工程系
107
In this study, Au-CsPbBr3 and PEDOT:PSS were spin-coated on an etched ITO (Indium Tin Oxide) substrate using a spin coater under normal atmosphere, and then moved to a nitrogen-filled glove box, MAPbI3 was coated on ITO substrate with Au-CsPbBr3 and PEDOT:PSS thin film. Then Evaporation of C60 using a vapor deposition system to form a film, return to glove box and then carry out the MAPbI3 layer heating action to make the film more uniform, and sent back to the thermal evaportation of Ag, and finally made into a perovskite solar cell of Glass/ITO/Au-CsPbBr3/PEDOT:PSS/MAPBI3/C60/Ag, with Au-CsPbBr3 as increase light trapping into the PEDOT:PSS hole transmission layer by the nano-particles through the surface plasmon resonance, MAPbI3 as a light absorbing layer, and C60 a crts as an electron transport layer. This study is mainly to addition of nano-gold particles in QD CsPbBr3 was achieved by local surface plasmon resonance. Then applied to cell, further synthesize of QD CsPbBr3 and added nano-gold particles on the characteristics of solar cells on the tradition structure of MAPbI3. For the characteristic analysis of the components,using a field emission scanning electron microscope(SEM) to analysis morphology of the thin film, X-Ray diffractometer analyzes crystal orientation, lattice constant, and grain size changes, the Ultraviolet/visible spectrophotometer analysis of its penetration, absorption spectrum, optical excitation light measurement system to analyze the optical properties, the component part is measured by a solar simulator to measure its J-V curve to obtain its open-circuit voltage (Voc), current density (Jsc), fill factor (FF), and photoelectric conversion efficiency (EQE).

博士
國立臺灣大學
材料科學與工程學研究所
104
We have employed the first-principle calculations to investigate the interfaces of 2D materials in the first part. The considered 2D materials are graphene and its derivatives, MoS2 and hexagonal boron nitride. These 2D materials can be stacked horizontally or vertically. Both of them show special properties and would have some special applications. We research graphene-based horizontal junctions, MoS2-based horizontal junctions and graphene/h-BN/graphene vertical junctions. For horizontal junctions, we focus on Schottky barrier heights, i.e., band alignments. For vertical ones, they can be applied as tunneling junctions; hence band alignments under electric fields are important. This junction can be potentially used in the nanoelectronics. Secondly, we investigate the optical transitions of perovskite MAPbI3. This material is widely used in the active layer of the solar cell device currently because of the strong absorption near visible-light region and the high power conversion efficiency of the device. Therefore, the optical transition near visible-light region would be the key factor. The band-resolved absorption density analysis is applied to investigate the optical transition mechanism.

碩士
中華科技大學
機電光工程研究所碩士班
105
In this work, we developed planar perovskite solar cells using CH3NH3PbI3 (MAPbI3) perovskites on oblique ITO substrates prepared glancing angle deposition (GLAD) method. This study investigated the optical, structural, and surface properties of the MAPbI3 perovskite films on oblique ITO substrates with treatment of different thermal annealing temperatures and different sputtering times. The relationship between the perovskite solar cells performance and the corresponding properties of the perovskite films is also discussed. The grain size of the MAPbI3 perovskite films increases with an increase in the sputtered oblique angle for the fabrication of ITO thin films increases from 0 o to 80 o, which indicates that the surface properties of the ITO influences the number of perovskite nucleation sites. The optimum power conversion efficiency (Eff) is achieved 11.3% for the cell with an oblique ITO layer prepared by sputtered angle of 30O for 15 min sputtering time.

碩士
國立臺灣大學
光電工程學研究所
107
Nowadays, the environmental issues are gradually becomes a major issues in our society where the pollution caused by fossil energy or nuclear energies are no longer accepted by our society. Thus, developing the green energy source becomes our future trends. Among green energy sources, solar cells has highest potential to becomes one major energy source in the near future. In the thesis, we will work on Perovskite based solar cells. Perovskite solar cells are rapidly developed in nine years. The efficiency of Perovskite solar cells has increased from 3.8% in 2009 to 23.3% in 2018. PEDOT:PSS/CH3NH3PbI3(MAPbI3)/PCBM has been studied in the thesis. In thesis, we simulated optical field by calculating in 2D Finite-Difference Time-Domain method (2D-FDTD). From optical field, we can analyze the distribution of generation rate and improve structure and thickness of device. Moreover, we simulated electric field by 2D drift-diffusion charge control solver (2D-DDCC). Studies shows that with an appropriate curve shape at surface of the thin film can improving light trapping, which is like the effect of convex lens. As changing amplitude of curve shape and period length, light trapping in the thin film changes. From improving structure, we can make the light to be full absorbed in the active layer of the solar cell to optimize the efficiency. By adjusting appropriate curve shape on surface of the thin film and period length, efficiency increases from 18.94% to 21.56%. If MAPbI3 lifetime is 1000 ns, efficiency even approaches 23.71%.

碩士
國立中山大學
材料與光電科學學系研究所
107
This dissertation involves two parts of investigations about the inverse temperature crystallization (ITC) growth perovskite: MAPbI3 single crystals. The first part is to study MAI-PbI2-GBL intermediate structure. The second part studies the influence of impurities in low-purity lead iodide (Lead (II) Iodide, PbI2, 99%) on the growth of MAPbI3 single crystal. We also apply acetonitrile (ACN) to help the dissolution of MAI and PbI2 powders into GBL. In the first part, yellow precipitant was fabricated from MAPbI3 in GBL solution. The precipitant was analyzed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Our results indicate the precipitant is composed of MAI-PbI2-GBL, and it can be further converted into MAPbI3 by thermal treatment to 110°C. In the second part, it was observed that MAPbI3 single crystal could not be produced by using low purity (99%) PbI2. Solutions with different purity raw materials were compared side-by-side. The solution with high purity raw materials was found to be darker than the other solution, and the absorption also exhibited to a longer wavelength. Mass spectroscopy was also performed for the identification of the impurities. Moreover, it was found that acetonitrile (ACN) can convert MAI and PbI2 into MAPbI3, despite the solubility of these materials in the solution was extremely low. The process accelerates the dissolution of the raw materials in the GBL solution, and also improves the quality of the single crystals grown by the solutions.

Perovskite solar cells (PSC) are one of the most promising photovoltaic (PV) technologies due to their quick and simple production, as well as their exceptional optoelectronic properties. However, their high price compared to the commercialized Si-based solar cells and their low scalability are some drawbacks that must be overcome. In this thesis, these drawbacks were surpassed by substituting the costly materials by low-cost alternatives. Instead of Spiro-OMeTAD [1] as the hole transport material (HTM), a much cheaper material, CuSCN was used [2]. Furthermore, all the fabrication processes were performed in air under ambient conditions, avoiding the high cost and scalability problems associated with the use of a glove box. Considering this philosophy of low-cost development of the PSCs, the active layer was composed by MAI and PbI2 as the precursors, which were dissolved in γ-Butyrolactone (GBL), while maintaining the TiO2 as the electron transport material (ETM). Incisive analysis of the individual layers of the solar cells were performed by many characterization tools such as spectrophotometry, XRD and SEM-EDS. As a result of several optimizations, a solar cell with VOC, JSC, FF and PCE values of 0.86 V, 15.29 mA/cm2, 0.64 and 8.48%, respectively was fabricated surpassing the previous efficiency record of 6.35% obtained in previous works [3].

Solar energy exploitation via photovoltaic (PV) technology has become the main route to achieve sustainable development. The emerging perovskite-based PV is considered one of the most promising alternative technologies to the conventional Silicon solar cells, since perovskites are a class of semiconductor materials with quite favourable optoelectronic proprieties that allow attaining high sunlight-to-electricity conversion efficiency. The main objective of this work is to improve the performance of perovskite solar cells (PSCs) using low-cost techniques and materials. Here, the perovskite (CH3NH3PbI3) is produced as the active layer, Titania (TiO2) and copper thiocyanate (CuSCN) are used as the electrons and holes transport layers, respectively. The production of homogeneous films is performed via spin-coating without atmospheric control, which is a great challenge in this area. In addition, the use of the inexpensive CuSCN hole transporter is developed, since it is 200 times less expensive than the conventionally-used Spiro-OMeTAD. This thesis was also investigated the crystallinity and quality of the perovskite film by a range of characterization tools such as XRD, SEM-EDS, AFM and UV-visible spectroscopy; as well as the influence of moisture on the active layer. The optimization of the fabrication methods was performed successfully, as demonstrated by the achievement of perovskite films with an absorbance of approximately 90-95% and large grain sizes of 333 ± 94 nm, allowing a PSC efficiency of 6.35%, with VOC of 0.89V, JSC of 15.46 mA/cm2, FF of 0.46, RSH of 2516 Ω and RS of 356 Ω.