Photo‐Induced Electrical Gating with the Inserting of an Interfacial Carrier Blocking Layer for Organic/Graphene Phototransistors

Abstract

AbstractAlthough ultrahigh photoconductive gain is achieved in organic semiconductor‐sensitized graphene phototransistors, the response speed is limited by the photo‐induced carrier injection at the organic/graphene interface. In this work, an insulating hexagonal boron nitride layer is inserted between the organic heterostructure and graphene to block the interfacial carrier transport. Above the h‐BN layer, the organic heterostructure is adopted as the light‐absorbing layer, and the photoresponse of graphene is realized through electrical gating of the atop h‐BN dielectric layer, by the accumulated carriers in the organic heterostructure. Under this “photo‐induced electrical gating” mechanism, the recombination of nonequilibrium carriers takes place only within the organic heterostructure. Furthermore, monolayer perylene‐3,4,9,10‐tetracarboxylic dianhydride (PTCDA) is deposited on graphene before transfer of the h‐BN, by which the interfacial encapsulated bubbles are effectively reduced. As a step further, the trap states are pre‐filled with background light illumination, then the carrier recombination follows the band‐to‐band pathway. Finally, the response time of the organic/h‐BN/graphene phototransistor is reduced to 7.15 ms, and a high photoresponsivity is achieved even though the carrier multiplication is sacrificed, which is reconciled by the improvement of the device quantum efficiency.