The preparation and characterization of Ga-doped CuInS2 films with chemical bath deposition

Ga-doped CuInS2 films were prepared on indium–tin–oxide substrates by chemical-bath-deposition method. The XRD diffractograms demonstrate that CuInS2 is the major crystalline phase of the as-prepared films. In addition, the doping density and flat band potential of the Ga-doped CuInS2 electrodes were measured with impedance spectroscopy based on the Mott–Schottky equation. With Ga molar ratios in the bath solution higher than 0.2, the semiconductor property of the sample was changed from n- to p-type. Additionally, the values of energy band gap and carrier densities of the Ga-doped samples were found in the range of 1.50–1.51 eV and 2.07×1015–4.50×1015 cm−3, respectively. Furthermore, the maximum photocurrent density of the as-prepared film was −1.28 mA/cm2 (with an external potential set at −1.0 V) when subject to the illumination of a 300 Xe lamp. These visible-light responsive properties assure their promising applications in photo-absorbing layers for photovoltaic cells or photocatalysts for hydrogen production.