Department of Materials Science and Engineering, Yonsei University, Korea
Photoelectrochemical (PEC) water splitting has also drawn significant attention as a cost-effective approach to accomplish solar hydrogen production because photoelectrode in PEC device simultaneously functions as a light harvester and electrolysis. In order to reduce the cost of solar hydrogen, earth-abundant light absorber materials should be accomplished with low-cost solution processing. In this talk, we will give a brief overview of recent progress in solution-processed photocathodes with earth-abundant constituents. Among the emerging photocathode materials, antimony selenide (Sb2Se3) is an attractive one due to the narrow band gap of 1.0 - 1.3 eV, high absorption coefficient (>105 cm-1) and high hole mobility. Moreover, Sb2Se3 is simple binary compound only having a thermodynamically stable orthorhombic phase, which allows avoiding the complexity of phase and defect control as encountered in other low-cost p-type semiconductor. We fabricated shape-controlled Sb2Se3 nanostructures via a facile spin-coating with molecular inks. The underlying unique growth mechanism of Sb2Se3 nanostructures was elucidated based on understanding of molecular chemistry. The molecular inks were derived from mixtures of thiol-amine, so-called “alkahest”, which have been known as a strong solvent system capable of dissolving diverse compound including metals, oxides and chalcogenides. High-quality metal chalcogenides were obtained by sequential coating molecular solution and annealing. With the controlled shaped Sb2Se3 nanostructures, the subsequent deposition of protection layer (TiO2) and co-catalyst for hydrogen evolution (Pt, RuOx, MoSx) enabled us to demonstrate promising performances, exceeding 30 mA cm-2 at 0 V vs reversible hydrogen electrode (RHE) under AM 1.5 G illumination, and stability over 10 h.