Low-Temperature Interfacial States of MoS₂-Pentacene Heterojunctions

Layered 2D materials such as transition metal dichalcogenides are fundamental components for building more complex heterostructures using organic molecules, nanostructures, or other layered materials. Organic thin film solids of pentacene, a well understood polycyclic aromatic hydrocarbon used commonly for photovoltaics and thin-film FETs, has been used to form mixed dimensional p-n heterojunctions with 2D MoS₂, wherein the type II band alignment leads to ultrafast hole transfer across the junction. Here, we report low temperature optical spectroscopy showing distinct optical features that emerge in the pentacene-MoS₂ heterostructure. We observe the quenching of pentacene singlet/triplet-emission and of MoS₂ defect photoluminescence as well as the emergence of a narrow emission feature at low temperatures. The power dependence and lack of response to local back-gating suggest these effects are not from charge doping or bound excitons. These results demonstrate the diverse control over opto-electronic properties obtainable by combining low-dimensional materials.