Modeling and optimization of CuIn1-xGaxSe2/Si1-yGey structure for solar cells applications

Abstract

A combination of a Copper Indium Gallium Selenide (CIGS) and Silicon (Si) layer has been recognized as an excellent choice for producing heterojunction based solar cells with improved efficiency and low cost processing techniques. The quaternary compound CIGS and silicon (Si) regions exhibit a lattice mismatch of about 5%, which induces a strain and impacts the electronic characteristics of the CIGS/Si heterojunction solar cell. A new viewpoint suggests the integration of a silicon germanium (Si1-yGey) layer in the CIGS/Si region to reduce the impact of lattice mismatch. The objective of this study is to investigate how different gallium and germanium concentrations (xGa and yGe) affect the following factors: lattice mismatch (ε), critical thickness (hc) and absorption coefficient (α)of CIGS/SiGe based solar cells. It also aims to analyze how these concentrations impact the primary parameters used to evaluate solar cell performance such as external quantum efficiency, short circuit current density, fill factor, open circuit voltage and conversion efficiency. The simulation results agree well with the existing theoretical and experimental literature data, confirming the suitability of the physical characteristics employed in this numerical study. By tuning the concentrations of Gallium and Germanium, it is feasible to attain an efficiency of 24% owing to the lattice compensation phenomenon in Si1-yGey layers. These findings hold significant implications for the development and advancement of solar cell technology, as well as for enhancing their conversion efficiency and commercialization.