Fabrication of CuInSe2 films and solar cells by the sequential evaporation of In2Se3 and Cu2Se binary compounds

Cu2Se/InxSe(x≈1) double layers were prepared by sequentially evaporating In2Se3 and Cu2Se binary compounds at room temperature on glass or Mo-coated glass substrates and CuInSe2 films were formed by annealing them in a Se atmosphere at 550°C in the same vacuum chamber. The InxSe thickness was fixed at 1 μm and the Cu2Se thickness was varied from 0.2 to 0.5 μm. The CuInSe2 films were single phase and the compositions were Cu-rich when the Cu2Se thickness was above 0.35 μm. And then, a thin CuIn3Se5 layer was formed on the top of the CuInSe2 film by co-evaporating In2Se3 and Se at 550°C. When the thickness of CuIn3Se5 layer was about 150 nm, the CuInSe2 cell showed the active area efficiency of 5.4% with Voc=286 mV, Jsc=36 mA/cm2 and FF=0.52. As the CuIn3Se5 thickness increased further, the efficiency decreased.