Organic charge-transfer interface enhanced graphene hybrid phototransistors

Abstract

Benefited from the advantages of light sensitivity of organic materials and high carrier mobility of graphene, organic semiconductor/graphene hybrid phototransistors exhibit ultrahigh photoconductive gain and photoresponsivity, attributed to the carrier multiplication effect in the organic layer. However, with single absorbing layer, the built-in electrical field between organic layer and graphene is insufficient, and spectral response range is limited. In this work, perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) organic tandem structure with high crystal quality fabricated via van der Waals vapor phase growth is adopted as the light absorbing layer, where suppressed carrier trap states density along with the additional charge-transfer interface between the organic layers result in overall improvement of device performance. Prominent photo-responses are observed with photoresponsivity up to 5.76 × 105A/W and photoconductive gain up to 1.38 × 109. Further more, complementary light absorption spectrum of these two organic materials fulfills effective photodetecting at ultraviolet and visible range.