Photo-Responsive Molecular Junctions Activated by Perovskite/Graphene Heterostructure Electrode

Abstract

Photoresponsivity is a fundamental process that constitutes optoelectronic devices. In molecular junction devices, one of the most adopted strategies is to employ photoactive molecules that can undergo conformational change upon light illumination as the conduction channel. However, such devices suffer from their relatively low photoresponsivity, long switching time, and unidirectional switching. In this study, the authors employed organohalide perovskite (OHP)/graphene heterojunction as a photoactive electrode that acted a source of photo-generated carriers collected as photocurrent in self-assembled monolayer (SAM)-based molecular junctions. This hybrid device architecture of perovskite/graphene/SAM allows the molecular junctions to attain a high photoresponsivity with molecules that have intrinsically little photoresponse. The authors elucidate the role of the molecular SAM in enhancing the photoresponsivity by systematically examining the transport and charge transfer processes at the graphene/SAM interface via molecules with different intrinsic dipole moments. This, corroborated with a theoretical analysis, reveals the origin of the observed photoresponsivity as light-induced coupling between the SAM and the OHP/graphene electrode within the orbital-mediated resonant tunnelling transport regime. These findings advance the understanding of photo-induced charge transport in molecular junctions with heterointerfaces, providing a road-map for designing high-performance molecular optoelectronic devices based on hybrid device architecture.