Enhanced bulk photovoltaic effect in two-dimensional ferroelectric CuInP2S6

While magnetism, hyperferroelectricity, and topological phases in the two-dimensional limit have been widely explored, the direct experimental study on bulk photovoltaic effect in 2D materials remains unimplemented. Here, the authors find bulk photovoltaic effect in 2D ferroelectric CuInP2S6. The photocurrent generation in photovoltaics relies essentially on the interface of p-n junction or Schottky barrier with the photoelectric efficiency constrained by the Shockley-Queisser limit. The recent progress has shown a promising route to surpass this limit via the bulk photovoltaic effect for crystals without inversion symmetry. Here we report the bulk photovoltaic effect in two-dimensional ferroelectric CuInP2S6 with enhanced photocurrent density by two orders of magnitude higher than conventional bulk ferroelectric perovskite oxides. The bulk photovoltaic effect is inherently associated to the room-temperature polar ordering in two-dimensional CuInP2S6. We also demonstrate a crossover from two-dimensional to three-dimensional bulk photovoltaic effect with the observation of a dramatic decrease in photocurrent density when the thickness of the two-dimensional material exceeds the free path length at around 40 nm. This work spotlights the potential application of ultrathin two-dimensional ferroelectric materials for the third-generation photovoltaic cells.

Automated summary

While magnetism, hyperferroelectricity, and topological phases have been extensively studied in two-dimensional materials, direct experimental investigation of the bulk photovoltaic effect in such materials remains unexplored. The authors of this study discovered the bulk photovoltaic effect in the 2D ferroelectric CuInP2S6. This work highlights the potential use of ultrathin two-dimensional ferroelectric materials for third-generation photovoltaic cells, surpassing the efficiency limits set by traditional p-n junction or Schottky barrier interfaces.