Solution-Processable Cu3BiS3 Thin Films: Growth Process Insights and Increased Charge Generation Properties by Interface Modification

Cu3BiS3 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 degrees 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 Cu3BiS3 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 TiO2/Cu3BiS3 heterojunctions can be significantly improved by the introduction of an In2S3 interlayer, and long-lived charge carriers (t50% of 10 mu s) are found.