Exploiting the Photoresponse in LiInP₂Se₆ for Image Processing

We report an anomalous photoresponse in LiInP₂Se₆-gated monolayer MoS₂ field effect transistors (FETs), driven by sub-bandgap photocarrier excitation and relaxation in LiInP₂Se₆. The MoS₂/LiInP₂Se₆ heterostructure exhibits gate-tunable persistent negative photoconductivity, a rare phenomenon in 2D FET platforms. Notably, the photoconductivity change scales with incident light intensity, with weaker illumination producing slower, smaller responses and stronger illumination inducing faster, stronger suppression. Exploiting the nonlinear, intensity-dependent photoresponse of LiInP₂Se₆, we demonstrate an image-processing platform that enables contrast modulation directly at the sensor level. By varying two controllable parameters, namely, applied top-gate bias and light exposure time, the device response can be tuned to modify the contrast of the image. This intrinsic behavior illustrates how contrast tunability can be achieved on a chip, offering a simple and compact route toward elementary preprocessing functions in vision devices.