A Cascade Bilayer Electron-Transporting Layer for Enhanced Performance and Stability of Self-Powered All-Inorganic Perovskite Photodetectors

This study aims to enhance optoelectronic properties of all-inorganic perovskite photodetectors (PDs) by incorporating a bilayer electron transport layer (ETL). The bilayer ETL composed of SnO₂ and ZnO effectively optimizes energy level alignment at the interface, facilitating efficient electron extraction from the CsPbI₂Br perovskite layer while suppressing shunt pathways. Additionally, it enhances interfacial properties by mitigating defects and minimizing dark current leakage, thereby improving overall device performance. As a result, the bilayer ETL-based PDs exhibit broadband photoresponsivity in 300 to 700 nm with a responsivity of 0.45 A W^-1 and a specific detectivity of 9 × 10¹³ Jones, outperforming the single-ETL devices. Additionally, they demonstrate stable cyclic photoresponsivity with fast response times (14 μs for turn-on and 32 μs for turn-off). The bilayer ETL also improves long-term reliability and thermal stability, highlighting its potential for high performance, reliability, and practical applications of all-inorganic perovskite PDs.