Photogating through Unidirectional Charge Carrier Funneling in Two-Dimensional Transition Metal Dichalcogenide/Perovskite Heterostructure Photodetectors

Two-dimensional (2D) van der Waals (vdW) semiconductors such as transition metal dichalcogenides (TMDCs) or 2D halide perovskites receive increasing attention as active materials in photosensing applications due to their high oscillator strength, large electronic mobility, and mechanical flexibility. For triggering an efficient separation of optically generated charge carriers and hence improving the photodetectivity, different vdW semiconductors are combined into functional heterostructures, i.e., TMDCs and 2D Ruddlesden-Popper perovskite. However, despite their increasing usage in devices, energy and charge carrier transfer between TMDCs and 2D Ruddlesden-Popper materials is still controversially discussed, and the underlying mechanisms of device operation are ambiguous. Here, in molybdenum disulfide/butylammonium lead iodide (MoS2/BA2PbI4) heterostructures, we demonstrate a unidirectional hole transfer from MoS2 to BA2PbI4 and an electron blocking through the butylammonium ions. MoS2/BA2PbI4 photodetectors show drastically improved responsivities, reduced dark current, and an increased detectivity compared to MoS2- and BA2PbI4-only devices. We provide evidence that this improvement is related to a gain mechanism due to photogating in the MoS2 channel caused by the unidirectional hole transfer between MoS2 and the BA2PbI4.