Aqueous‐Based Low‐Temperature Synthesis and Thin‐Film Properties of Oxysulfide BiCuOS Nanoparticles

BiCuOS is a nontoxic p‐type semiconductor that is a promising candidate for photoelectric applications. The formation of thin films with a good electronic transport at the grain boundaries, while avoiding thermal treatment detrimental to its chemical stability is a challenge. We have developed a chemical method for the direct synthesis of stable colloidal suspensions of BiCuOS nanoparticles from soluble precursors. These colloidal solutions were stabilized with a catechol functionalized poly‐3‐hexylthiophene that allows easy spin‐coating deposition and favors electronic transport along the grain boundaries. Stacking of ZnO–BiCuOS layers were achieved, allowing preparation of n–p junctions. These act as rectifying diodes and are strongly photosensitive, with Iph/Idark=85 corresponding to an enhancement of the photocurrent of more than two orders of magnitude compared to that of BiCuOS alone. This energy‐efficient and low‐cost method is a further step in the development of new sulfide semiconductor devices. Nanoparticles for diodes: Oxysulfide BiCuOS nanoparticles were synthesized through a well‐controlled wet‐chemistry route at low temperature in water. A thin film of these nanoplatelets was then obtained by the deposition of a colloidal ink onto an FTO/ZnO substrate to form a p‐n junction. This acts as a strongly photosensitive diode with Iph/Idark=85, corresponding to an increase of more than two orders of magnitude compared to that of BiCuOS alone.