Exploiting the Photoresponse in LiInP 2 Se 6 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.