Study of RF Sputtered Antimony Alloyed Bismuth Vanadium Oxide (Sb:BiVO4) Thin Films for Enhanced Photoelectrochemical (PEC) performance from Bandgap Modulation to Thickness Optimization

TL;DR

This study demonstrates that antimony alloying effectively reduces the band gap of BiVO4 to 1.72 eV, enhancing its photoelectrochemical water splitting performance through controlled fabrication and optimization of film properties.

Contribution

First demonstration of Sb alloying in BiVO4 thin films via RF sputtering to achieve a lower band gap and improved PEC performance with optimized thickness and surface treatments.

Findings

Band gap reduced to 1.72 eV by Sb alloying.

Optimal film thickness of 400 nm for maximum photocurrent.

Sb:BiVO4 exhibits improved hole diffusion length.

Abstract

Monoclinic scheelite bismuth vanadate (BiVO4) is a promising photoanode for water splitting yet the PEC performance is limited due to its relatively higher (2.4 eV) band gap. Here, we successfully decreased its the band gap to 1.72 eV by controlled antimony alloying. Low bandgap antimony alloyed bismuth vanadium oxide (Sb:BiVO4) thin film was prepared by RF sputtering of high purity homemade target, fabricated by solid-state reaction using a mixture of Sb2O3, Bi2O3, and V2O5 powders with desired stoichiometric ratios. Several growth parameters, powder crystallography, post-deposition effects, and surface treatments, thickness dependence, effect of electrolytes on photocorrosion were studied along with its optical and electrochemical characterization. We discovered that Sb:BiVO4 is a direct band gap material in the visible light range (1.72 eV) and a valence band position suitable for driving water oxidation reaction under illumination. Furthermore, hole diffusion length is increased with antimony alloying and achieved optimum thickness of 400 nm for higher photocurrent. The controllably prepared Sb:BiVO4 particles are having the sizes of 10-15 nm in room temperature deposition and can be grown up to 0.5 microns under air annealing.