Light‐Programmable Positive‐Negative Photoconductivity Dual‐Mode Photodetection based on Up‐Conversion Nanoparticles/Perovskite Heterostructures

Abstract Conventional photodetectors for single‐band detection can hardly meet the ever‐increasing desire for instantaneous interpretation of the diversified optical information due to the limited integration level. Here, the perovskite/NaYGdF 4 up‐conversion nanoparticles (UCNPs) photodetectors demonstrate with an excellent ability for simultaneous recognition of the wavelength and light intensity based on the light positive photoconductive (PPC) and negative photoconductive (NPC) effects. The NPC effect can be derived from the trapping effect of the up‐conversion layers, endowing the controllable photo‐resistance by incorporation with UCNPs via a systematic variation of defect state density. Thus, the positive response is observed with the responsivity (R) of 41.22 mA W −1 and detectivity (D*) of 3 × 10⁸ Jones under 500 nm illumination at 10 V, and the device exhibits the negative response with the R of 100.24 µA W −1 and D* of 7.91 × 10⁵ Jones under 980 nm illumination, resulting in an excellent spectral distinguishability at each light intensity with the recognition ratio of 3.9 × 10⁵ suggests. The light‐programmable evolution of image definition is further visualized with a bimodal encoding image accumulator system.