Efficiency enhancement of CZTSe solar cell using CdS(n)/(AgxCu1–x)2ZnSnSe4 (p) /Cu2ZnSnSe4 (p+) structure

Abstract

Direct bandgap Cu2ZnSnSe4 (CZTSe) material is a promising absorber for thin film photovoltaics due to its affordable production cost and ecofriendly constituents. However, bulk defects, small grain size, short minority carrier lifetime and band bending at CZTSe/Mo (back contact) interface limit the performance of CZTSe solar cells. To overcome these issues, we design a single junction CdS(n)/ (AgxCu1–x)2ZnSnSe4 (p) /Cu2ZnSnSe4 (p + ) solar cell where we use (AgxCu1–x)2ZnSnSe4 (ACZTSe) as the main absorber layer. We have chosen the carrier density of each layer in a such way that ACZTSe becomes depleted and generated minority are collected efficiently. In our design, we utilize CZTSe as the back surface field layer to prevent surface recombination and indium doped tin oxide (ITO) as the back electrode to avoid band bending and increase the open circuit voltage. Additionally, we optimize the thicknesses of different layers and achieve a maximum efficiency of 18.63% including Shockley-Read-Hall, radiative and surface recombination mechanisms. The photo conversion efficiency (PCE) of our designed solar cell is 6% higher (12.6% vs 18.63%) than that of the best reported selenium rich CZTSe solar cell. The design concept proposed in this work would help in harvesting solar energy efficiently from next generation CZTSe solar cells.