الفهرس 
CHAPTER 1: INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
In recent years, the photovoltaic technology contributes a large amount of electric power generation worldwide. It has many advantages over other electrical sources competitors such as source, low manufacturing and maintenance costs. Perovskites materials have the potential to contribute to wide application due to their high power conversion efficiency and compatibility with easy fabrication processes. Tin-based perovskite is a famous member in the lead-free perovskite solar cells family. However, tin-based perovskites have some issues that limit their performance; such as oxidation of positive tin ions when exposed to air and the poor film quality. That is why recombination is significant in such cells and low open circuit voltage and power efficiency are usually obtained.
In this work, a device enhancement of FASnI3-based solar cells is performed. Design parameters are chosen such that they have enhanced performance and they can be easily changed practically. The device simulator (SCAPS) is used to validate our work by comparing the initial performance with literature measurements. It also used to inspect the impact of design parameters on cell performance and choose the optimum values. Further, SCAPS simulator allows us to investigate various HTL and ETL candidates. The results, after optimization, are short-circuit current density (Jsc) of 22.65 mA/cm2, open-circuit voltage (Voc) of 0.92 V, fill factor (FF) of 67.74% and power conversion efficiency (PCE) of 14.03%.
Single solar cell suffers from two basic types of losses: First, the transmission losses due to the unabsorbed photons. Second, the thermalization losses result from relaxation of hot carriers. These phenomena limit the energy conversion efficiency of a single solar cell to a thermodynamic limit called Shockley and Queisser limit. On other hand, using tandem or multi-junction solar cell with different bandgaps materials arranged in rows is a suitable way to capture a wider bandgap of solar spectrum.
In this work also, we design a two-terminal monolithic all lead-free tandem solar cell. The (MASnI3) cell with 1.3 eV bandgap is used as a bottom cell and the top cell is (MASnIBr2) with a bandgap of 1.75 eV.An7.66% efficient tandem cell is obtained with a matching current of 10.36 mA/cm2after comprising these two initial sub-cells. After optimization of the individual cells, the tandem efficiency and the matching current improve to 15.66% and 13.94mA/cm2respectively. In addition, current matching point is tracked at various bandgaps and thicknesses. The simulations done here show the significant influence of current matching point on tandem cell performance. The thesis provides a theoretical study that could provide a guide for experimental work.