Abstract
The performance of a BiVO4 photoanode is limited by poor charge transport, especially under front side illumination. Heterojunction of different metal oxides with staggered band configuration is a promising route, as it facilitates charge separation/transport and thereby improves photoactivity. We report a ternary planar heterojunction photoanode with enhanced photoactivity under front side illumination. SnO2/WO3/BiVO4 films were fabricated through electron beam deposition and subsequent wet chemical method. Remarkably high external quantum efficiency of ~80% during back side and ~90% upon front side illumination at a wavelength of 400 nm has been witnessed for SnO2/WO3/BiVO4 at 1.23 V vs. reversible hydrogen electrode (RHE). The intimate contact between the heterojunction films enabled efficient charge separation at the interface and promoted electron transport. This work provides a new paradigm for designing triple heterojunction to improve photoactivity, particularly under front illumination, which would be beneficial for the development of tandem devices.
Highlights
Since we are heavily dependent on fossil fuels, harvesting clean energy in an efficient way is a pressing problem for mankind
Photoelectrochemical water splitting offers the capabilities to harness sunlight and convert it in the form of chemical storage through chemical bonds in the form of hydrogen [1,2,3,4]
Triple planar double heterojunction SnO2 /WO3 /BiVO4 photoanode has been fabricated through the combination of electron beam (e-beam) deposition and metal organic decomposition (MOD)
Summary
Since we are heavily dependent on fossil fuels, harvesting clean energy in an efficient way is a pressing problem for mankind. Due to short electron diffusion length, BiVO4 exhibits high photocurrent density under backside illumination. It is necessary to fabricate BiVO4 photoanode which delivers superior pec performance during front side illumination. This would help in designing the future energy materials for the industrial scale applications. There have been few reports of BiVO4 with heterojunction showing enhanced water oxidation performance under front illumination [22,23]. BiVO4 /WO3 type II heterojunctions have been intensively constructed in order to improve the light absorption capacity [25]. We have studied SnO2 /WO3 /BiVO4 triple planar double heterojunction with different thicknesses and observed the change in the behavior of front illumination performance. This study would be beneficial for the construction of efficient tandem devices
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