Photo-Gating through Unidirectional Charge Carrier Funneling in 2D TMDC / 2D Perovskite Heterostructure-Photodetectors

<br/>Two-dimensional (2D) van der Waals (vdW) semiconductors, such as transition-metal dichalcogenides (TMDCs), have garnered increasing attention as promising materials for photosensing applications. Their appeal lies in their high oscillator strength, significant electronic mobility, and remarkable mechanical flexibility, promising novel application scenarios for optical sensing in healthcare, optical communication or different lifestyle applications. However, due to their intrinsically limited light absorption, high responsivities and sensitivities are hard to achieve. To enhance photodetectivity, TMDCs are frequently integrated into functional heterostructures with other vdW semiconductors like 2D Ruddlesden-Popper Perovskites to introduce a gain mechanism. However, the processes of energy and charge carrier transfer between TMDCs and 2D Ruddlesden-Popper materials remain subjects of debate, making it challenging to elucidate the fundamental mechanism of device operation.<br/>In this study, we present lateral heterostructure photodetectors composed of MOCVD-grown molybdenum disulfide (MoS2) and solution processed butylammonium lead iodide (BA₂PbI₄) that exhibit significantly enhanced responsivities, reduced dark current, and increased detectivity when compared to devices using MoS₂ or BA₂PbI₄ alone. We provide compelling evidence that this improvement is linked to a gain mechanism facilitated by photo-gating within the MoS₂ channel. This photo-gating results from a unidirectional transfer of holes from MoS₂ to BA₂PbI₄ and the blocking of electrons by butylammonium ions. Our devices exhibit responsivities up to 10 A/W, which corresponds to a gain of 145. This research sheds light on the intriguing performance of heterostructure photodetectors based on 2D materials and their potential for practical device integration.