Abstract
Determining cost-effective semiconductors exhibiting desirable properties for commercial photoelectrochemical water splitting remains a challenge. Herein, we report a Sb2Se3 semiconductor that satisfies most requirements for an ideal high-performance photoelectrode, including a small band gap and favourable cost, optoelectronic properties, processability, and photocorrosion stability. Strong anisotropy, a major issue for Sb2Se3, is resolved by suppressing growth kinetics via close space sublimation to obtain high-quality compact thin films with favourable crystallographic orientation. The Sb2Se3 photocathode exhibits a high photocurrent density of almost 30 mA cm−2 at 0 V against the reversible hydrogen electrode, the highest value so far. We demonstrate unassisted solar overall water splitting by combining the optimised Sb2Se3 photocathode with a BiVO4 photoanode, achieving a solar-to-hydrogen efficiency of 1.5% with stability over 10 h under simulated 1 sun conditions employing a broad range of solar fluxes. Low-cost Sb2Se3 can thus be an attractive breakthrough material for commercial solar fuel production.
Highlights
Determining cost-effective semiconductors exhibiting desirable properties for commercial photoelectrochemical water splitting remains a challenge
The Eg of Cu2ZnSn(S,Se)[4] semiconductor, which is another earth-abundant material applicable for PEC water splitting, varies from 1.0 to 1.5 eV depending on the composition, the pure-phase compound suffers from severe difficulty of synthesis due to the narrow stoichiometric window[12]
There were some pin-holes resulting in exposure of the substrate with the faceted morphology of the Sb2Se3 thin films
Summary
Determining cost-effective semiconductors exhibiting desirable properties for commercial photoelectrochemical water splitting remains a challenge. We report a Sb2Se3 semiconductor that satisfies most requirements for an ideal high-performance photoelectrode, including a small band gap and favourable cost, optoelectronic properties, processability, and photocorrosion stability. As the solar-to-hydrogen (STH) efficiency of PEC devices using expensive photovoltaic-grade III–V semiconductors has approached the theoretical maximum[1], the research community is recognising the importance of exploring low-cost materials exhibiting good optoelectronic properties[2]. With this consideration, most recent critical evaluations[3,4,5] pertaining to artificial photosynthesis have urged the development of new light absorbers. As molecular inks for Sb2Se3 already contain 1D [Sb4Se7]2− chains in the solution[24,27], it is a daunting task to obtain compact thin Sb2Se3 films via solution processing
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