Homotypic heterojunction of metal oxygen/sulfide as an electron transport layer for high-performance perovskite solar cells

Abstract

The electron transport layer (ETL), as a critical component of a perovskite solar cell structure, establishes an electron-selective contact with the perovskite absorber layer. In this work, the synthesized SnS₂ nanosheets are introduced into a SnO₂ film to prepare a SnS₂–SnO₂ homotypic heterojunction (HHJ) as an efficient electron transport material. The electron migration gradient formed in the prepared heterojunction structure is able to provide the driving force to regulate electron transport, enabling efficient extraction and transportation of electrons through various migration routes. The results of the study reveal that the SnS₂–SnO₂ ETL promotes vertical growth of the perovskite crystals owing to its bottom-up S–Pb coordination and wettability. Additionally, the SnS₂–SnO₂ HHJ promotes the regulation of electron migration and the reduction of interfacial non-radiative recombination, resulting in improvement in the optoelectronic performance of the device. Consequently, a photoelectric conversion efficiency of 19.98% is achieved in the optimized device prepared under ambient conditions in comparison to the control device (16.74%), with negligible hysteresis and enhanced hydrothermal stability of the device.