Synthesis and Characterization of Nanostructured Wurtzite CuInS2: A New Cation Disordered Polymorph of CuInS2

A new wurtzite (WZ) structure CuInS2, space group P6(3)mc, a = 3.90652(13) angstrom, c = 6.42896(23) angstrom, has been synthesized by a one-step solvothermal method. Analogous with the disordered zinc-blende structure, wurtzite structure is metastable at room temperature and considered as a disordered polymorph of chalcopyrite (CH) structure, where Cu and In atoms randomly occupy the cation sublattice positions. It is believed that the solvent of ethanolamine plays an important role in the synthesis of WZ-CuInS2. The coordination between Cu2+ and -NH2 of ethanolamine molecules favors the nucleation and growth of WZ-CuInS2. Differential scanning calorimeter, together with X-ray diffraction analysis, revealed a phase transition from WZ-CuInS2 to CH-CuInS2 when WZ-CuInS2 was heated to certain temperature. The visible and near-infrared absorption spectra show that the as-prepared nanostructured WZ-CuInS2 has distinct optical properties compared with conventional CH-CuInS2.