Tunable Negative and Positive Photoconductance in Van Der Waals Heterostructure for Image Preprocessing.

The processing of visual information occurs mainly in the retina, and the retinal preprocessing function greatly improves the transmission quality and efficiency of visual information. The artificial retina system provides a promising path to efficient image processing. Here, we propose graphene/InSe/h-BN heterogeneous structure, which exhibits negative and positive photoconductance effects by altering the strength of a single wavelength laser. Moreover, we present a modified theoretical model based on the power-dependent photoconductivity effect of laser: I ph = - mP α 1 + nP α 2 $\rm I_{\rm ph}\,=\,\rm {-mP}^{\rm \alpha _{1}} + \rm {nP}^{\rm \alpha _{2}}$ , which can reveal the internal physical mechanism of negative/positive photoconductance effects. The present two-dimensional (2D) structure design allows the field effect transistor (FET) to exhibit excellent photoelectric performance (R NPC  = 1.1× 10 4  A/w, R PPC  = 13 A/w) and performance stability. Especially, the retinal pretreatment process is successfully simulated based on the negative and positive photoconductive effects. Moreover, the pulse signal input improves the device responsivity by 167%, and the transmission quality and efficiency of the visual signal can also be enhanced. This work provides a new design idea and direction for the construction of artificial vision, and lay a foundation for the integration of the next generation of optoelectronic devices. This article is protected by copyright. All rights reserved.