Maxwell–Wagner polarization engineering in ferroelectric photovoltaic effect

Ferroelectric photovoltaic cells have attracted particular interest owing to their potential applications in the green energy field. But there are two drawbacks: weak polarization and wide bandgap, which make them suffer from the limitation of energy conversion efficiency. In this study, the key issue is solved in Ag2O nanoparticle-dispersed Bi5Ti3FeO15 composites. In order to clarify the mechanism, performances of the bandgap, polarization-dependent J–V curves, dielectric response, and switchable photocurrents were investigated. The Maxwell–Wagner polarization effect is confirmed by permittivity Cole–Cole plots with two or more semicircles overlapping. The spatial polarization gradient matrices can reduce the effective mass of the electron–hole pairs and further promote their separation via the Maxwell–Wagner polarization effect. The synchronous mobility of the separated carriers is enhanced. An improved ferroelectric photovoltaics is achieved in Bi5Ti3FeO15⋅3%Ag2O composites, and the key parameters are as follows: VOC ∼ −3.1 V, energy converse efficiency 9.2 × 10−4%. Furthermore, this work shows the first step toward polarization gradient composites for application in ferroelectric photovoltaic cells.