Colloidal synthesis of wurtzite Cu2CoSnS4 nanocrystals and the photoresponse of spray-deposited thin films

Monodisperse nanocrystals of a new wurtzite phase of Cu2CoSnS4 (CCTS) have been synthesized using a simple solution-based method. The wurtzite CCTS nanocrystals grow in the shape of nanorods with an average length of 32 +/- 2.0 and width of 16 +/- 1.5 nm. The more stable stannite phase of CCTS has also been synthesized by increasing the reaction temperature or by a post-high-temperature annealing process. The band gap of wurtzite CCTS nanocrystals is determined to be 1.58 eV. Thin films prepared from the nanocrystal suspension display photoresponse behaviour with white light from a solar simulator, suggesting the potential use of CCTS as an active layer in low-cost thin-film solar cells.