Graphene/PbS-Quantum Dots/Graphene Sandwich Structures Enabled by Laser Shock Imprinting for High Performance Photodetectors.

Quantum dots (QDs) integrated 2-dimensional (2D) materials have great potential for photodetector applications due to the excellent light absorption of QDs and ultrafast carrier transportation of 2D materials. However, there is a main issue that prevents efficient carrier transportation and ideal performance of photodetectors: the high interfacial resistance between 2D materials and QDs due to the bad contacts between 2D/0D interface, which makes sluggish carrier transfer from QDs to 2D materials. Here, a sandwich structure (graphene/PbS-QDs/graphene) with seamless 2D/0D contact was fabricated by laser shock imprinting, which opto-mechanically tunes the morphology of 2D materials to perfectly wrap on 0D materials and efficiently collect carriers from the PbS-QDs. It is found that this seamless integrated 2D/0D/2D structure significantly enhanced the carrier transmission, photoresponse gain (by 2×), response time (by 20×), and photoresponse speed (by 13×). The response time (∼30 ms) and I/ I ratio (13.2) are both over 10× better than the reported hybrid graphene photodetectors. This is due to the tight contact and efficient gate-modulated carrier injection from PbS-QDs to graphene. The gate voltage dictates whether electrons or holes dominate the carrier injection from PbS-QDs to graphene.