Enhancing electron extraction and transport in inorganic perovskite solar cells via additional built-in potential of SnO2-BiFeO3 nano-heterostructure

The electron transport layer (ETL) with excellent charge extraction and transport ability plays a crucial role in high-performance perovskite solar cells (PSCs). Here, we propose a approach to modify SnO2 ETL by introducing perovskite oxide BiFeO3 nanoparticles into SnO2 film to construct SnO2-BiFeO3 nano-heterostructure. The formation of SnO2-BiFeO3 nano-heterostructure within the SnO2 ETL introduces an additional built-in potential directed from SnO2 to BiFeO3, which provides an additional driven force for the charge carriers transfer. As a result, the extraction rate of electrons from the perovskite layer to the SnO2-BiFeO3 ETLs is significantly improved. In addition, an excellent ETL/perovskite interface with more favorable band alignment and fewer defects is achieved via the incorporation of BiFeO3 nanoparticles. By employing SnO2-BiFeO3 ETLs in CsPbI3 PSCs, we obtained PSC with a higher PCE of 17.35%, compared to 14.93% for the reference one. This result not only validates the effectiveness of BiFeO3 in improving the performance of SnO2-based PSCs but also highlights its potential application for other perovskite devices.