Self-powered bifunctional perovskite photodetectors with both broadband and narrowband photoresponse

Photodetectors generally operate exclusively in either the broadband or narrowband. Developing bifunctional photodetectors that can detect photons in both broadband and narrowband would bring significant versatility to the optoelectronic platform. Nevertheless, the design of bifunctional integrated devices remains challenging due to the differentiated strategies with respect to device structure and material combination. Herein, we propose introducing polyvinylpyrrolidone to increase the viscosity of the perovskite precursor solution, which introduces abundant defects and cavities into the perovskite film while maintaining a relatively low film thickness. Then, we use methylamine gas to postprocess the middle area of the film to promote directional recrystallization and densification, thereby realizing narrowband and broadband dual-function photodetection in a single device at zero bias. Both ends of the film exhibit a near-infrared peak response at 780 nm with a narrow full-width at half maximum of approximately 30 nm without an external bias. The middle broadband photodetector exhibits a high responsivity of 329 mA W⁻¹ and EQE up to 52.46% at 780 nm. We make full use of narrow-band wavelength selective detection and broadband full-spectrum detection to achieve double encryption during signal transmission. This work represents an important step toward the realization of perovskite-based multifunctional integrated devices.