Domain switching-induced large rigid shift of the bulk photovoltaic effect in (111)-oriented BiFeO3 epitaxial films

The bulk photovoltaic effect (BPVE) in ferroelectric materials exhibits intrinsic sensitivity to light polarization, offering opportunities for self-powered polarization photodetection. However, the impact of ferroelectric domain switching on BPVE and its underlying mechanism remain insufficiently understood. Herein, we report the first experimental demonstration of electric-field modulation of BPVE in (111)-oriented BiFeO3 (BFO) epitaxial films. The (111)-oriented devices exhibit a continuous and rigid vertical shift (i.e., photocurrent offset) of the BPVE curves under external electric field, while preserving their amplitude and phase, in contrast to the (001) counterparts. Notably, the photocurrent modulation range along the in-plane electrode direction is four times larger than that of (001)-oriented devices. Piezoresponse force microscopy and crystal structure analysis reveal multidirectional domain switching in the (111)-oriented BFO films, which continuously modulates the interfacial Schottky barriers, thus accounts for the observed rigid shift. These findings elucidate the orientation dependent electric-field tuning mechanism of BPVE and highlight the advantage of (111)-oriented BFO for polarization-sensitive photodetector applications.