Simulation and Optimization of CIGS Solar Cells in Concentrated Sunlight
Abstract
Chalcopyrite Solar cells based on copper-indium-gallium-diselenide (CIGS) absorbers demonstrate the highest efficiencies of all thin film photovoltaic technologies. In the recent years, laboratory scale cells have reached efficiencies of about 20% and this technology has received significant funding to support its growth. Simulations of CIGS solar cells can help designers to examine and evaluate their limiting factors and employ proper techniques to overcome them. In this work, we simulate single-crystal CIGS solar cells with different absorber thicknesses and compositions, different grading ratios and different doping concentrations when considering some defect densities. Moreover, we have added grain boundaries in the structure of our cell's absorber layer in order to have a qualitative look at the effects of poly-crystalline boundaries in charge carriers' recombination rate and their influence on efficiency. Furthermore, we compared our results for the cells with and without boundaries. This comparison helps one to understand the impact of morphology in a CIGS solar cell on its efficiency. In addition, we performed all of our simulations in higher concentrations of sunlight in order to optimize the grading ratio and doping concentration in these conditions for obtaining the highest efficiency.