Copper indium gallium disulphide (CuInGaS2) thin films deposited by spray pyrolysis for solar cells: influence of deposition time in controlling properties of sprayed CuInGaS2 absorbers

CuInGaS2 (CIGS) multi-component semiconductors thin films were elaborated by spray pyrolysis on glass substrates using different spray times. The structural, optical and electrical properties of CuInGaS2 thin films were investigated. The obtained films were characterized using X-ray diffraction, Raman spectroscopy (RS), UV-Vis spectrophotometer and Hall Effect measurement. Thin films were formed by varying deposition time in the range, 30-50 min, keeping other deposition parameters as constant. The X-ray spectra revealed that the CuInGaS2 thin films have chalcopyrite structures with a highly (112) preferential orientation. The best crystallinity is obtained for HK-50 the maximum (112) peak intensity. RS also confirmed this structure. Optical constants such as band gap (Eg), extinction coefficient (k), refractive index (n), dielectric constants (epsilon(r)) and (epsilon(i)) and optical conductivity (sigma(opt)) were calculated from the measured transmittance and absorption spectra in the wavelength range between 550 and 900 nm. The bulk concentration, mobility (mu), conductivity (sigma), resistivity (rho) and conduction type of thin films obtained at different deposition times were determined using Hall Effect measurements. It has been observed that the optimum time of spray was 50 min for best performed CuInGaS2 thin films with low resistivity and high mobility. Deposition time has been discussed to obtain the high quality thin film absorbers for solar cell applications. Here, we report a study on structural, optical and electrical properties of CuInGaS2 films grown by chemical spray pyrolysis in view of its application as an absorber in thin film solar cells.