Physical studies of CuIn1-xGaxSe2/Si1-yGey

Abstract

The importance of combining the Copper Indium Gallium Selenide (CIGS) and Silicon (Si) for solar cell technologies outruns the limitations for their commercialization and the conversion efficiency limits. The lattice mismatch (about 5%) between chalcopyrite quaternary (CIGS) and silicon (Si) regions induces strain, affecting the electronic properties of the CIGS/Si hetero-junction solar cell, an innovative view suggests inserting a silicon germanium (Si1-yGey) layer into CIGS/Si interface to reduce the lattice mismatch effects. The impact of varying gallium and germanium concentrations (xGa and yGe) on the lattice mismatch, critical thickness and absorption coefficient of CIGS/SiGe based solar cells is investigated. As well as their effects on the main parameters used to characterize the performance of solar cells such as external quantum efficiency, open circuit voltage, short current density, fill factor and the conversion efficiency. Good agreement between simulation results and both existing theoretical and experimental literature data proves adequacy of the physical properties used in this numerical investigation. Optimizing Gallium and Germanium concentrations makes it possible to achieve an efficiency of 24% due to the lattice compensation effect in Si1-yGey layers.