Synthesis of CuInS₂ by sulfide ion-exchange of CuIn(OH)₅ precursors

CuInS₂ semiconductor was synthesized from CuIn(OH)₅ precursors via facile anion exchange in aqueous Na₂S solution at room temperature. CuIn(OH)₅ was prepared from copper and indium salts and NaOH by co-precipitation in aqueous solution as a polycrystalline. The sulfide exchange reaction did not alter the copper to indium ratio. The reaction resulted in stoichiometric amounts of sulfur in the CuInS₂ sample at room temperature. Fourier transform infrared spectra and ion chromatography were used to analyze the impurities, including chloride and nitrate in the prepared samples. CuInS₂ showed a chalcopyrite crystal structure after annealing at 500°C under 4% hydrogen-mixed argon atmosphere. The bandgap of the CuInS₂ thin film device was estimated to be 1.46 eV.