Synthesis of CuInSe2 films via selenizing the Cu–In alloy-containing nanopowders

CuInSe2 thin films were prepared employing nanopowders consisting of Cu–In alloys and In as the precursors of selenization. The nanopowders were synthesized via the chemical reduction method using NaBH4 as the reductant and water as the solvent. On selenization at 350 °C, CuInSe2 started to form along with the intermediate compounds of copper selenides. The sizes of the grains in the thin films were significantly increased at 450 °C because of the existence of Cu–Se phases. When the selenization temperature was raised to 550 °C, the densified CuInSe2 films with a grain size of around 2 μm were observed. The formation and uniformity of single-phase CuInSe2 throughout the thin film were verified via grazing incident X-ray diffraction. The Raman spectroscopy and the Rietveld refinement method confirmed the pure chalcopyrite phase of CuInSe2. The band gap of the CuInSe2 thin film was measured to be 0.97 eV via the UV–visible–NIR spectroscopy. The CuInSe2 thin-film solar cells exhibited a photovoltaic conversion efficiency of 1.47% under AM 1.5 G illumination.

► A non-vacuum process using nanopowders was developed for preparing CuInSe2.
► These nanopowders were obtained at low temperatures in ambient atmosphere.
► The densified CuInSe2 films with a grain size of around 2 μm were prepared.
► Raman analysis and Rietveld refinement method confirmed the pure phase of CuInSe2.
► The photovoltaic conversion efficiency of CuInSe2 thin-film solar cells was 1.47%.