Bulk photovoltaic effect in two-dimensional ferroelectric α-In₂Se₃

Non-centrosymmetric material systems can generate spontaneous photocurrent without a p-n junction under uniform illumination, which is known as the bulk photovoltaic effect (BPVE). It has garnered significant attention for its application potential in the fields of energy harvesting and photoelectric detection. In this study, we report the BPVE observed in two-dimensional ferroelectric α-In₂Se₃ multilayer flakes. The reversal in spontaneous photocurrent polarity is observed and associated with the out-of-plane ferroelectric polarization direction. The spontaneous photocurrent originating from the shift current is also polarization-sensitive. The amplitude of spontaneous photocurrent is further increased by one order of magnitude through vacuum annealing. Our results provide a further application potential for new-generation photodetectors based on BPVE with low power consumption and multi-dimensional optoelectronic detection.