Diffuse Ferroelectric\nPhase Transition-Dependent Photovoltaic\nEffect in BiFeO<sub>3</sub>–BaTiO<sub>3</sub>‑Based\nSolid Solutions

The photovoltaic effect in ferroelectric (FE) semiconductors,\ni.e.,\nthe FPV effect, is attracting increasing attention. However, the microscopic\nmechanism of the FPV effect is still largely unknown. Here, we investigated\nthe effects of crystal structure, dielectric, FE, and domain features\non the FPV effect in the 0.7BiFe<sub>1–<i>x</i></sub>Cr<sub><i>x</i></sub>O<sub>3</sub>-0.3BaTi<sub>1–<i>x</i></sub>Mn<sub><i>x</i></sub>O<sub>3</sub> (BFC-BTM)\n(0.01 ≤ <i>x</i> ≤ 0.07) system. We observed\na coexisting rhombohedral and tetragonal to pseudocubic phase transition\nfor <i>x</i> ≥ 0.05. This structural transition was\naccompanied by a significant reduction in the lattice distortion and\ndisappearance of macro-sized FE domains. We found a substantial increase\nand decrease in the degree of the diffuseness of the relaxor FE phase\ntransition and the open-circuit photovoltage <i>V</i><sub>OC</sub>, respectively, for <i>x</i> ≥ 0.05, in\ncontrast to the relatively weak variation in the remnant polarization.\nOur results demonstrate that the FPV effect depends weakly on FE polarization\nbut strongly on the complex submicron domain-related diffused relaxor\nFE phase transition and crystal structure in BFC-BTM. These results\nwere discussed based on the non-centrosymmetry-related shift current\nmechanism.