InCl3-modified SnO2 as an electron transporting layer for Cd-free antimony selenide solar cells

Abstract

Solar cells based on Sb₂Se₃ have attracted increasing attention due to its excellent optoelectronic properties and low-cost fabrication. Up to now, high-efficiency Sb₂Se₃ solar cells with a superstrate structure have always used CdS as an electron transport layer (ETL). However, the parasitic absorption caused by CdS reduces the light absorption of the Sb₂Se₃ absorber layer, and combined with the toxicity of the Cd element, jointly causes its limitation in practical application. Tin oxide (SnO₂) is a wide-bandgap ETL and has been widely used in solar cells due to its suitable energy level, high electron mobility, and good stability. However, Sb₂Se₃ films deposited on metal oxides always exhibit poor quality. In this study, we demonstrate a facile strategy to improve the quality of an Sb₂Se₃ film by modifying a SnO₂ layer with InCl₃. We find that InCl₃ post-treatment can optimize the band alignment between SnO₂ and Sb₂Se₃, improve the quality of the SnO₂/Sb₂Se₃ heterojunction, and reduce deep-level defects. As a result, the PCE improves from 1.51% to 5.52%. Thus, this work offers a simple and effective way to improve the quality of Sb₂Se₃ films deposited on SnO₂ ETLs and provides a new path towards fabricating Cd-free Sb₂Se₃ solar cells.