Enhanced bulk photovoltaic effect in two-dimensional ferroelectric CuInP2S6

Abstract The photocurrent generation in photovoltaics relies essentially on the interface of p-n junction or Schottey barrier with the photoelectric efficiency constrained by the Shockley-Queisser limit. The recent progresses have shown a promising route to surpass this limit via the bulk photovoltaic effect (BPVE) for crystals without inversion symmetry. Here we report the BPVE in two-dimensional (2D) ferroelectric CuInP 2 S 6 with enhanced photocurrent density by two orders of magnitude higher than conventional bulk ferroelectric perovskite oxides. The BPVE is inherently associated to the room-temperature polar ordering in 2D CuInP 2 S 6 . We also demonstrate a crossover from 2D to 3D BPVE material with the observation of a dramatic decrease in photocurrent density when the thickness of the 2D material exceeds the free path length (\({l}_{0}\)) at around 40 nm. This work spotlights the potential application of ultrathin 2D ferroelectric materials for the third-generation photovoltaic cells.