Strong Light-Matter Interactions in Heterostructures of Atomically Thin Films

TLDR

The isolation of two‑dimensional materials and their vertical stacking has created a new paradigm in materials science, enabling heterostructures that have already proven fruitful for ultrathin, flexible electronic devices. The study aims to extend 2D heterostructures to photoactive devices by integrating semiconducting transition‑metal dichalcogenides with graphene. The authors exploit Van Hove singularities in the electronic density of states of the TMDCs to enhance light‑matter interactions, enabling efficient photon absorption and electron‑hole generation collected by transparent graphene electrodes. This approach yields extremely efficient flexible photovoltaic devices with photoresponsivity above 0.1 A W⁻¹, corresponding to an external quantum efficiency exceeding 30 %.

Abstract

The isolation of various two-dimensional (2D) materials, and the possibility to combine them in vertical stacks, has created a new paradigm in materials science: heterostructures based on 2D crystals. Such a concept has already proven fruitful for a number of electronic applications in the area of ultrathin and flexible devices. Here, we expand the range of such structures to photoactive ones by using semiconducting transition metal dichalcogenides (TMDCs)/graphene stacks. Van Hove singularities in the electronic density of states of TMDC guarantees enhanced light-matter interactions, leading to enhanced photon absorption and electron-hole creation (which are collected in transparent graphene electrodes). This allows development of extremely efficient flexible photovoltaic devices with photoresponsivity above 0.1 ampere per watt (corresponding to an external quantum efficiency of above 30%).