Solution-Processable Cu 3 BiS 3 Thin Films: Growth Process Insights and Increased Charge Generation Properties by Interface Modification.

Cu 3 BiS 3 thin films are fabricated via spin coating of precursor solutions containing copper and bismuth xanthates onto planar glass substrates or mesoporous metal oxide scaffolds followed by annealing at 300 °C to convert the metal xanthates into copper bismuth sulfide. Detailed insights into the film formation are gained from time-resolved simultaneous small and wide angle X-ray scattering measurements. The Cu 3 BiS 3 films show a high absorption coefficient and a band gap of 1.55 eV, which makes them attractive for application in photovoltaic devices. Transient absorption spectroscopic measurements reveal that charge generation yields in mesoporous TiO 2 /Cu 3 BiS 3 heterojunctions can be significantly improved by the introduction of an In 2 S 3 interlayer, and long-lived charge carriers ( t 50% of 10 μs) are found.