Structural and optical properties of Zn doped CuInS2 thin films

Copper indium sulphide (CIS) films were deposited by spray pyrolysis onto glass substrates from aqueous solutions of copper (II) sulphate, indium chloride and thiourea using compressed air as the carrier gas. The copper/indium molar ratio (Cu/In) in the solution 1(1:1) and the sulphur/copper ratio (S/Cu) was fixed at 4. The structural properties of these films were characterized. The effects of Zn [(0%-5%) molecular weight compared with CuInS2 Source] and different substrate temperatures on films properties were investigated using X-ray diffraction (XRD) and optical transmission Spectra. Optical characteristics of the CuInS2 films have been analyzed using spectrophotometer in the wavelength range of 300-1100 nm. The absorption spectra of the films showed that this compound is a direct band gap material and gap values varied between 1.55-1.57 eV, depending on the substrate temperatures. The Zn-doped samples have band gap energy of 1.55-1.95 eV. It was observed that there is an increase in optical band gap with increasing Zn % molecular weight. The optical constants of the deposited films were obtained from the analysis of the experimental recorded transmission and absorption Spectral data The refractive index n and dielectric constants epsilon(1) and epsilon(2) were also discussed and calculated as a function of investigated wavelength range and found it dependent on Zn incorporation. We found that the Zn-doped CuInS2 thin films exhibit P-type conductivity and we predict that Zn species can be considered as suitable candidates for use as doped acceptors to fabricate CuInS2-based solar cells. The paper presents a study concerning the influence of deposition parameters (temperature of the substrate and concentration of Zn (1-5)% from 0.16 M ZnCl2) on the quality of CuInS2 thin films achieved by spray pyrolysis on glass substrate from solutions containing0.02 M CuCl2 center dot 2H(2)O, 0.16 M thiourea and 0.08 M In2Cl3 center dot 5H(2)O.