Theoretical Investigation on Improvement of CIGS-based Solar Cells

As the energy demand continues to increase, the need for various energy sources is evident. The renewable energy sources provide sustainable and environmentally friendly energy, which can be alternative to traditional energy. Solar cells are the widespread forms of renewable energy. Many materials have been developed to produce thin-film solar cells. The Cu(In, Ga)Se2 (CIGS)-based solar cell is considered as one of the most promising thin-film solar cells due to its many attractive features. In this paper, numerical simulations of thin-film CIGS solar cells using two-dimensional device simulator called Silvaco-Atlas are presented. Several studies of CIGS solar cell structures have been examined by employing CdS as a buffer layer. In this scenario, we first investigate CIGS solar cell based on CdS as a buffer layer. The simulation results are compared with those of previous related experimental and theoretical studies. In addition, the photovoltaic parameters are in good agreement with the experimental ones, which validate our simulation model. Secondly, we examine CIGS solar cell based on ZnS as a buffer layer in order to enhance the power conversion efficiency of CIGS solar cells. Therefore, the photovoltaic parameters of CdS-CIGS solar cell design are compared with those of ZnS-CIGS solar cell design showing a significant improvement of efficiency by including ZnS buffer layer. In particular, the efficiency increases from 22.92 % to 24.4 %. Moreover, an optimization process is applied to ZnS-CIGS solar cell design, which gives an efficiency of 25.1 %. The proposed CIGS solar cell design may significantly enhance the solar cell performances. Thus, ZnS can be considered as a promising alternative buffer layer for improving thin-film CIGS solar cell efficiency.