-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.