Synergistic Interfacial Engineering With Butylamine Hydrochloride (BACl)‐Doped PCBM Enables Four‐Orders‐of‐Magnitude Responsivity Enhancement in Planar CsPbI 3 Photodetectors

Jones, and a fast response time of 40 µs. Furthermore, the modified device exhibits outstanding operational and storage stability: under continuous 660 nm illumination for 6 h, it shows only a 15.9% fluctuation in the light on-off ratio, vastly outperforming the pristine device (99.5%). After 500 h of storage in a glove box, it retains 48% of its initial photoresponsivity, while the pristine device loses all photosensitivity. This work highlights multifunctional ETL doping as a simple route to high-performance perovskite photodetectors.