Synthesis of oleic acid-capped CuInS2 nanocrystals from bimetallic hydroxide precursor

CuInS2 colloidal nanocrystals were synthesized via a facile solution-processed method, using a CuIn(OH)5 precursor. The Cu-In metal hydroxide precursor was prepared by co-precipitation in aqueous solution: an aqueous NaOH solution was reacted with a metal cation solution containing Cu2 + and In3 + ions at room temperature. Oleic acid was added as a surfactant and bis(trimethyldisilyl)sulfide was injected to provide a sulfur source for the formation of CuInS2 nanocrystals. The CuInS2 colloidal nanocrystals had mixed crystal structures of zincblende and wurtzite, confirmed by XRD and TEM. The CuInS2 nanoparticles were of average size 5.6 nm and had a 1:1:2 chemical composition. Paste of the as-prepared CuInS2 nanocrystals were coated as a thin film absorber layer for photovoltaic cells by doctor blading, yielding cell efficiency of 1.26%.