Thiol‐Amine‐Based Solution Processing of Cu(2)S Thin Films for Photoelectrochemical Water Splitting

Cu(2)S is a promising solar energy conversion material owing to its good optical properties, elemental earth abundance, and low cost. However, simple and cheap methods to prepare phase‐pure and photo‐active Cu(2)S thin films are lacking. This study concerns the development of a cost‐effective and high‐throughput method that consists of dissolving high‐purity commercial Cu(2)S powder in a thiol‐amine solvent mixture followed by spin coating and low‐temperature annealing to obtain phase‐pure crystalline low chalcocite Cu(2)S thin films. After coupling with a CdS buffer layer, a TiO(2) protective layer and a RuO( x ) hydrogen evolution catalyst, the champion Cu(2)S photocathode gives a photocurrent density of 2.5 mA cm(−2) at −0.3 V vs. reversible hydrogen electrode (V(RHE)), an onset potential of 0.42 V(RHE), and high stability over 12 h in pH 7 buffer solution under AM1.5 G simulated sunlight illumination (100 mW cm(−2)). This is the first thiol‐amine‐based ink deposition strategy to prepare phase‐pure Cu(2)S thin films achieving decent photoelectrochemical performance, which will facilitate its future scalable application for solar‐driven hydrogen fuel production.