High-efficiency bulk photovoltaic effect with ferroelectric-increased shift current

Bulk photovoltaic (BPV) effect primarily stems from shift currents in symmetry-breaking materials, providing the potential to smash the Shockley-Queisser limit that constrains the performance of conventional p-n junctions-based solar cells. However, limited open circuit voltages (Voc) or short circuit current densities (Jsc) from BPV devices still cause a low photoelectric conversion efficiency. Here, combining theoretical analysis and experimental evidence, we identify a range of BPV materials where both Voc and Jsc can be co-optimized, and greatly boost the efficiency through ferroelectric engineered shift current. We select ferroelectric NbOBr2 as an example and construct a two-dimensional in-plane device with a giant shift current-dominated BPV effect. In spontaneous polarization state, the devices demonstrate a record-high Jsc among all ferroelectric materials. Moreover, the electrically aligned NbOBr2 polarization enables the significant co-enhancement of both Voc and Jsc, leading to a colossal improvement of photoelectric conversion efficiency up to four orders of magnitude (1.25%), which is approximately four times greater than that of state-of-the-art BPV devices. Our work provides a promising solution for screening and creating higher efficient BPV cells. The photoelectric conversion efficiency of bulk photovoltaic devices has been limited by open circuit voltages or short circuit current densities. Here, authors construct a 2D in-plane device based on ferroelectric NbOBr2 to improve photovoltaic performance and achieve a device efficiency of 1.25%.