Direct Synthesis of Highly Conductive tert-Butylthiol-Capped CuInS2 Nanocrystals

Abstract : tert-butylthiol (tBuSH) is used as the sulfur source, surface ligand and co-solvent in the synthesis of CuInS2 nanocrystals (NCs). The presented method gives direct access to short-ligand-capped NCs without post-synthetic ligand exchange. The obtained 5nm CuInS2 NCs crystallize in the cubic sphalerite phase with space group F-43m and a lattice parameter a=5.65 angstrom. Their comparably large optical and electrochemical band gap of 2.6-2.7eV is attributed to iodine incorporation into the crystal structure as reflected by the composition Cu1.04In0.96S1.84I0.62 determined by EDX. Conductivity measurements on thin films of the tBuSH-capped NCs result in a value of 2.5(.)10(-2)Sm(-1), which represents an increase by a factor of 400 compared to established dodecanethiol-capped CuInS2 NCs.