Highly Improved Quantum Efficiencies for Thin Film BiVO4 Photoanodes

BiVO4 has received much recent interest as a promising photocatalyst for oxygen evolution from water, but little is known about the factors that limit its performance as a photoanode. In this article, we report on highly efficient and reproducible BiVO4 photoanodes prepared by a new spray pyrolysis recipe. For undoped films deposited on a transparent conducting substrate (F-doped SnO2, FTO), electron transport and charge collection at the back-contact were found to limit the photoresponse. Electron transport could be greatly enhanced by donor-doping with 1% W, while the charge collection problem has been solved by introducing a thin (similar to 10 nm) interfacial layer of SnO2 in between the FTO and the BiVO4. This layer presumably acts as a hole mirror that recombination via FTO-related defect states at the FTO/BiVO4 interface. By addressing these two issues, the external quantum efficiency (IPCE) of spray-deposited BiVO4 films was improved by a factor of similar to 7, leading to an unprecedented IPCE of 46% (at 450 nm) at 1.63 V-RHE for 1% W-doped BiVO4 films deposited on FTO/SnO2.