Bulk photovoltaic effect in a two-dimensional ferroelectric semiconductor α-InSe.

The bulk photovoltaic effect, arising from the separation of charge carriers driven by crystal symmetry, is an intriguing physical phenomenon that has been attracting broad interest in the field of photovoltaic applications due to its junction-free nature and potential to surpass the Shockley-Queisser limit. The photovoltaic applications of conventional ferroelectric materials with wide bandgaps (2.7-4 eV) are limited due to their low photocurrent densities and weak photovoltaic response in the visible light region. The emergence of two-dimensional ferroelectric semiconductors with coupled visible light absorption and spontaneous polarization characteristics is promising for the development of functional photoferroelectrics. Herein, we report the experimental demonstration of enhanced bulk photovoltaic response in a two-dimensional ferroelectric semiconductor α-InSe under the excitation of visible light. The generated photovoltaic current density is nearly two orders of magnitude higher than that of conventional bulk ferroelectric materials. Our findings highlight the potential of two-dimensional ferroelectric semiconductor materials for bulk photovoltaic applications across a broad spectral region.