Suppressing the Trapping Process by Interfacial Charge Extraction in Antimony Selenide Heterojunctions

The efficiency of antimony selenide (Sb2Se3) solar cells has been improved from <2% to >10% within only 7 years, but fundamental properties at the heterojunction interface such as the charge carrier transfer and the trap state localizing process has not been studied yet. Here, the carrier competing dynamics in Sb2Se3-based heterojunction has been systematically investigated. We find the competition between the band-edge electron transfer and the trapping process in CdS/Sb2Se3 will result in less-efficient charge separation and hence low open circuit voltage in photovoltaic devices. In contrast, the hot electron extraction at the SnO2/Sb2Se3 interface is nearly an order of magnitude faster than the trapping process, which can effectively escape the trapping carrier loss and potentially lead to higher open-circuit voltages. Our results reveal the hidden role of the buffer interface in the ultrafast charge extraction and provide a potential strategy to improve the performance of Sb2Se3-based solar cells.