Self‐Driven Perovskite Dual‐Band Photodetectors Enabled by a Charge Separation Reversion Mechanism

Abstract New mechanisms and modalities for multiband light detection are highly desirable for the ever‐growing developments in machine vision technologies. Demonstrated here is a unique talent of halide perovskites for making self‐driven dual‐band photodetectors with a negative broadband response in the above‐bandgap absorption region and a positive narrowband response in the sub‐bandgap absorption region. The device operates through a charge separation reversion mechanism by controlling the built‐in electric field and the thickness‐dependent light absorption profile in the active material. Impressively, the demarcation wavelengths between the negative broadband and the positive narrowband responses can be continuously adjusted, with the positive narrowband response easily tuned from 410 to 675 nm. The dual‐band photodetector exhibits an extremely low noise of 10⁻¹⁵ A Hz^−1/2 and a high specific detectivity of >10¹² Jones in both above‐bandgap and sub‐bandgap absorption regions, opening up application opportunities in intelligent recognition and biomedical diagnosis.