Perovskite Photodetectors With Customizable Frequency Response.

Photodetectors in emerging optoelectronic systems are increasingly required to deliver application-defined transfer characteristics rather than merely high responsivity or fast response. Existing response-engineering strategies mainly operate in the wavelength or intensity domains, but often increase source-side complexity, power consumption, and sensitivity to optical-path fluctuations. Here we introduce a frequency-centric strategy for response modulation. By combining a time-integrated-charge-based alternating-current-to-direct-current (AC-DC) mapping with continuous tuning of the built-in electric fields across heterojunction regions with antagonistic photoresponses, the transfer function becomes customizable in the frequency domain. Using lead-halide perovskites as a model platform, we demonstrate bipolar responses for image-processing, nonlinear responses for neuromorphic activation-function emulation, and selective responses for anti-interference free-space optical communication. The selective-response device suppresses stray illumination by more than three orders of magnitude, while the transmitter can be implemented using a conventional laser diode driven by a function generator. The extension of this strategy to PbS and PbI2-based systems supports its material generality, indicating a general route to photodetectors with application-defined response characteristics.