Development of co-evaporated In2S3 buffer layer for Cu2ZnSnSe4 thin film solar cells

In this work, we focus on the replacement of the commonly used but toxic Cd-based buffer layer by In₂S₃ thin films deposited by co-evaporation for application in Cu₂ZnSnSe₄ (CZTSe) solar cells. The impact of the deposition conditions of the buffer layer on the electrical behavior of CZTSe/In₂S₃ devices is first investigated. The best solar cell efficiencies were obtained for relatively thick In₂S₃ buffer layers (~100 nm) deposited at low temperature (<;100 °C). It is also observed that low [Cu]/([Zn]+[Sn]) ratio (CZT~0.75) in the kesterite absorber leads to high efficiency for In-based buffered CZTSe solar cells, while the effect of the CZT ratio on CZTSe/CdS solar cell performances is not so clear. A conversion efficiency of 5.7 % on CZTSe/In₂S₃ thin film solar cell is achieved.