Quantitative Assessment of Optical Gain and Loss in Submicron-TexturedCuIn1−xGaxSe2Solar Cells Fabricated by Three-Stage Coevaporation

CuIn${}_{1-x}$Ga${}_{x}$Se${}_{2}$ (CIGS) is an important photovoltaic material, but variations in composition and nanoscale textures that form naturally during processing thwart accurate modeling. The authors develop a general formalism to simulate the charge carrier collection in complex multilayered systems, permitting the calculation of the external quantum efficiency of a thin-film solar cell. For a realistic complicated system they find that the collection efficiency in the CIGS layer is almost 100%, while the light absorption in the 1-$\ensuremath{\mu}$m-thick bottom region is negligible.