One-pot thermolysis synthesis of CuInS2 nanoparticles with chalcopyrite-wurtzite polytypism structure

Abstract

CuInS 2 nanoparticles as the visible (wurtzite, 1.67 eV) or near infrared (chalcopyrite, 1.50 eV) light absorbing material in thin film solar cells, were synthesized using facile, one step heating up method by dissolving of CuCl, InCl 3 and SC(NH 2 ) 2 as precursors in oleylamine (OLA) alone or in combination with oleic acid (OA) and 1-octadecene (ODE) as solvent. The phase, size, morphology, and size distribution were controlled by the coordination ability between solvent molecules and metal precursors, reaction temperature and time. The presence of higher amounts of thiourea or OA to OLA led to the formation of chalcopyrite phase in comparison to wurtzite structure. Also, higher reaction temperatures ([240°C) resulted in favour of more chalcopyrite phase and higher crystallinity but the nanoparticles got agglomerated. As synthesized nanoparticles was characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, high resolution-transmission electronic microscopy, ultravioletvisible-near infrared, photoluminescence. The high resolution TEM confirmed the existence of chalcopyrite structure along with wurtzite structure in the nanocrystal (polytypism). Well controlled chalcopyrite CuInS 2 triangular pyramidal shape with an average size ranging from *10-20 nm size was obtained by using 20 ml OLA or 20 ml OLA along with 4 ml OA and ODE, respectively, with 210°C heating up and 4 h annealing time.

Oleic acid/oleylamine ligand pair: a versatile combination in the synthesis of colloidal nanoparticles

“…Increasing the thiourea to OAm ratio led to an enhancement in chalcopyrite production with respect to wurtzite. 187 In the case of the CuInS 2 system, it was reported that OAc could reduce the precursor reactivity, leading to a decrease in the population of nuclei formed during the nucleation step. Consequently, this would maintain the presence of a considerable quantity of precursors during the growth step, causing an increase in the NP size.…”