Photoresponse of an Organic Semiconductor/Two-Dimensional Transition Metal Dichalcogenide Heterojunction.

We study the optoelectronic properties of a type-II heterojunction (HJ) comprising a monolayer of the transition metal dichalcogenide (TMDC), WS, and a thin film of the organic semiconductor, 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA). Both theoretical and experimental investigations of the HJ indicate that Frenkel states in the organic layer and two-dimensional Wannier-Mott states in the TMDC dissociate to form hybrid charge transfer excitons at the interface that subsequently dissociate into free charges that are collected at opposing electrodes. A photodiode employing the HJ achieves a peak external quantum efficiency of 1.