An Aqueous Processed Photosensitive Bilayer van der Waals Thin Film for Flexible Neuromorphic Vision

Abstract

Printing colloidal ink of semiconductor nanocrystals, particularly 2D nanosheets, facilitates the generation of van der Waal's thin films (vdWTFs) with inherent flexibility and optoelectronic properties, ideal for wearable intelligence devices, such as bionic vision. Several intricate strategies, such as mechanical/electrochemical exfoliation and pulsed laser/chemical vapor, have been devised for producing solvent-dispersed nanosheets and corresponding vdWTFs; achieving efficient preparation via more environmentally friendly processes remains a challenge. Here, an ecofriendly aqueous approach for crafting vdWTF, relying on a gentle self-assembly C8-BTBT nanosheet aqueous ink, is demonstrated. The resulting vdWTF features a bilayer heterostructure, wherein a crystalline C8-BTBT nanosheet layer is staggeringly stacked atop a graphene oxide (GO) film. This configuration allows the sliding of the staggered 2D nanosheets, accommodating local tension and compression, thereby averting film breakage and ensuring desirable flexibility. Further, by harnessing the natural photosensitivity of C8-BTBT and the charge-trapping capabilities of GO component, the heterostructured bilayer vdWTFs confer exceptional photoperception and intrinsic persistent photoconductivity effects upon their flexible planar devices. These attributes enable the emulation of bio-visual behaviors such as short/long-term memory, light adaptation, reinforcement learning, and image recognition.