Thickness-Dependent Bulk Photovoltaic Effect and Ultrafast Response in 3R-MoS2

The emergence of 2D sliding ferroelectric semiconductor expands the ferroelectric materials family and provides an ideal platform for multifunctional applications. Specifically, the non-volatile ferroelectric polarization and bulk photovoltaic effect (BPVE) make them ideal candidates for self-powered photodetection. Photodetectors based on BPVE with a large ferroelectric polarization are highly desirable, due to the combination of high photo-response efficiency and ultrafast response. In this work, the thickness-dependent sliding ferroelectric BPVE and its ultrafast carrier dynamics in 3R-MoS₂ layers are investigated. The sliding ferroelectricity and its associated switchable BPVE response are confirmed at room temperature. With an approximate twofold increase in thickness, a near sevenfold enhancement in short-circuit current, and a tenfold rise in open-circuit voltage are observed, demonstrating an enhanced BPVE. More importantly, due to the enlarged polarization in thicker 3R-MoS₂, time-resolved photocurrent (TRPC) measurements reveal that the log-log slope of the response time versus thickness is less than 2, breaking through the conventional L² (thickness)-dependent limit of the drift-diffusion model, thereby enabling ultrafast response even in thick layers. This work provides a new pathway to high-performance ultrafast bulk photovoltaic photodetectors.