Influence of Sulfur Content in Zn(O,S) Buffer Layer onto Copper Indium Gallium Sulfur-Based Solar Cells Through Surface Engineering at ZnO1-xSx/CIGS Interface

Copper indium gallium sulfur (CIGS) solar cells show good efficiency; however, the buffer/absorber and absorber/back contact interfaces are the most critical factors affecting that efficiency. We have investigated CIGS-based solar cells with two different buffer layers, ZnO1-xSx and SnS2, a non-toxic alternative to CdS using a solar cell capacitance simulator. First, we propose a cell structure with a ZnO1-xSx/CIGS interface for different sulfur content in ZnO1-xSx. The band gap of ZnO1-xSx and the conduction band offset ( increment E-c) at the ZnO1-xSx /CIGS interface can be tuned by the sulfur content, enabling high efficiency. We found that the ZnO1-xSx buffer layer with a sulfur composition S/(O + S) ratio of 0.85 leads to enhanced performance of CIGS solar cells up to 23.94%. Above 0.85, the performance of the solar cells is affected, depending on its thickness and the carrier concentration of both absorber and buffer layers. The CIGS solar cell performance was evaluated using SnS2 as a buffer layer. The results show that the efficiency of CIGS-based solar cells with Zn(O0.30S0.79) and with SnS2 is slightly different, at 23.54% and 23.44%, respectively. In addition, there is a difference in the open-circuit voltage (V-oc) and short-circuit current density (J(sc)) due to the reduction in the interface recombination and band structure at the buffer/CIGS interface.

Automated summary

Copper indium gallium sulfur (CIGS) solar cells exhibit good efficiency, but the efficiency is greatly influenced by the buffer/absorber and absorber/back contact interfaces. This study investigates CIGS-based solar cells using two different buffer layers, ZnO1-xSx and SnS2, as non-toxic alternatives to CdS. Results show that a ZnO1-xSx buffer layer with a sulfur composition ratio of 0.85 leads to improved performance of CIGS solar cells up to 23.94%. Additionally, the use of SnS2 as a buffer layer slightly affects the efficiency and results in an efficiency of 23.44%.