Separation mechanism of photogenerated charges for p-type α-Bi2O3 nanoparticles with surface states

► α-Bi2O3 nanoparticles exhibit an obvious photovoltaic response from 325 to 500 nm with two ranges. ► The electric-field induced surface photovoltage spectroscopy presents different results under positive and negative bias. ► We analysed the micro-process of the separation of photogenerated charges for α-Bi2O3 and put forward the quantitative analysis. ► The build-in electric field due to Schottky barrier and surface states mainly contribute to the photovoltaic response.