Semiconductor Bandgap grading of Buffer layer for performance optimization of thin solar cells

Due to the low throughput and high-cost of Si-based Photovoltaic (PV) cells, alternatives such as thin-film PV cells based on Cu2ZnSnS4 (CZTS) and Cu2Sn1-xGexS3 (CTGS) are being sought. The buffer layer is very critical as it provides band-alignment at the absorber/window layer and also reduces defects/interfacial strain. The standard buffer layer of CdS for CIGS and CZTS has a bandgap around 2.7 eV, being detrimental for the performance of PV cells, necessitating alternative buffer layers of the higher bandgap. In this work, the role of bandgap variation has been analysed for performance optimization of CZTS based PV cells using SCAPS software. This study depicts that by bandgap grading through deploying alternative buffer materials, the performance of PV cells may be upgraded.