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‐MoS 2 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‐MoS 2 , 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 L 2 (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.