A comparative study on generation and recombination process of kesterite CZTS based thin film solar cells for different designs

In this paper, a comparative study on generation and recombination process in different CZTS designs has been carried out in which their performances and band alignment are invistigated. Firstly, CdS/CZTS design has been modeled using the SCAPS-1D. Secondely, new designs have been proposed in which a back surface field (BSF) layer is inserted and CdS layer is replaced by ZnS. The obtained results exhibit a boosted efficiency from 12.03 % to 14.14 % by inserting a BSF layer with a ZnS buffer layer. The analysis of generation and recombination reveals a high recombination in CdS/CZTS interface in comparaison with ZnS/CZTS due to the high density of defect states at the CdS/CZTS interface. BSF increases recombination in P-region. Whereas, it fairly impacts generation process. ZnS/CZTS/BSF design enhances the collection efficiency in short and long wave length regions resulting in higher solar cell performances (V-OC =0.89 V, J(SC) =25.38mA/cm(2), FF=62.44 %, eta=14.14 %).