BiVO4 thin film photoanodes grown by chemical vapor deposition

Abstract

BiVO₄ thin film photoanodes were grown by vapor transport chemical deposition on FTO/glass substrates. By controlling the flow rate, the temperatures of the Bi and V sources (Bi metal and V₂O₅ powder, respectively), and the temperature of the deposition zone in a two-zone furnace, single-phase monoclinic BiVO₄ thin films can be obtained. The CVD-grown films produce global AM1.5 photocurrent densities up to 1 mA cm⁻² in aqueous conditions in the presence of a sacrificial reagent. Front illuminated photocatalytic performance can be improved by inserting either a SnO₂ hole blocking layer and/or a thin, extrinsically Mo doped BiVO₄ layer between the FTO and the CVD-grown layer. The incident photon to current efficiency (IPCE), measured under front illumination, for BiVO₄ grown directly on FTO/glass is about 10% for wavelengths below 450 nm at a bias of +0.6 V vs. Ag/AgCl. For BiVO₄ grown on a 40 nm SnO₂/20 nm Mo-doped BiVO₄ back contact, the IPCE is increased to over 40% at wavelengths below 420 nm.