Enhanced electron lifetime in bismuth-vanadium-oxide based bifunctional hybrid photoactive heterostructures

The present work reports a systematic study on the structural, optoelectronic and photoelectrochemical properties in bismuth-vanadium-oxide (BVO) based thin films, produced by controlling the dilution and pH of the deposition solution. The obtained results from X-ray diffraction and diffuse reflectance spectroscopy revealed that the attenuation of the quantum confinement effect, due to the decrease of the crystallite size and the self-doping by Bi5+ in the Bi46V8O89 structure, promoted the reduction in the bandgap energy for the Bi46V8O89 phase from 2.93 eV (M-sample) to 2.50 eV (B-sample), while a bandgap around 2.41 eV was obtained for the Bi4V2O11 phase in the B-sample. Under illumination, the Bi5+–Bi46V8O89/Bi4V2O11 (B-sample) heterostructure showed a high electron lifetime value around 39 ms, while lower values were obtained for the M and A samples (around 0.017 ms and 0.07 ms, respectively) containing only the Bi46V8O89 phase. It was also verified by the Mott-Schottky analysis that the conductivity can be changed from n-type to p-type depending on the applied frequency and potential, thus opening new possibilities for the manufacture of BVO-based bifunctional photoelectrodes for application in optoelectronic devices.