Efficient Sb2(S,Se)3/Zn(O,S) solar cells with high open-circuit voltage by controlling sulfur content in the absorber-buffer layers

The purpose of this study is the efficiency improvement of the Sb2Se3 solar cells. In this study, an experimental Sb2Se3 solar cell (glass/Mo/MoSe2/Sb2Se3/CdS/ZnO/ZnO:Al/Ag) with an efficiency record of 9.2% has been simulated. Absorber/buffer interface engineering plays a significant role in enhancing the efficiency of Sb2Se3 solar cells. To achieve this purpose, two approaches have been considered: first, adding sulfur to Sb2Se3 absorber, and second, using an alternative buffer with a wider bandgap instead of conventional CdS buffer. The effects of various x = Se/(S + Se) ratios of Sb-2(S(1-x)Sex)(3) absorber layer on the photovoltaic performance were investigated. For Sb-2(S,Se)(3)/CdS solar cell, optimum Se/(S + Se) mole fraction of 0.6 < x < 0.8 leads to improved efficiency. Also, ZnO1-ySy buffer layer was applied to replace the conventional CdS buffer layer of Sb2Se3 solar cells to reduce parasitic absorption and improve the short-circuit current density (Jsc). Bandgap for ZnO1-ySy semiconductor is higher than CdS. So, this leads to improved external quantum efficiency at short wavelengths. Optimization of band alignment through ZnO1-ySy buffer layer reduces interface carrier recombination and improves open-circuit voltage (V-oc). The band alignment at the Sb-2(S(1-x)Sex)(3)/ZnO1-ySy interface is optimized by adjusting the selenium-to-sulfur ratio in the absorber layer and sulfur-to-oxygen ratio in the buffer layer. This work reveals that the most suitable interface for Sb-2(S1-xSex)(3)/ZnO1-ySy heterojunction is formed when sulfur mole fractions ranging 0.5-0.6 in the Zn(O,S) buffer layer and 0.1-0.2 in the Sb-2(S,Se)(3) absorber layer. The results show that the efficiency improves from 9.2% to 15.65%, which represents a 70% improvement compared with the conventional Sb2Se3/CdS solar cell.

Automated summary

The goal of this study is to improve the efficiency of Sb2Se3 solar cells through two approaches: adding sulfur to the absorber layer and using an alternative buffer layer with a wider bandgap. The research findings demonstrate that the efficiency can be increased from 9.2% to 15.65% by optimizing the band alignment at the interface.