Effect of temperature on structural, optical and photoluminescence properties of antimony (Sb) doped polycrystalline CuInS2 thin films prepared by spray pyrolysis

Copper indium disulphide (CuInS2) is an absorber material for solar cell and photovoltaic applications. By suitably doping CuInS2 thin films with dopants such as Zn, Cd, Na, Bi, Sn, N, P and As its structural, optical, photoluminescence properties and electrical conductivities could be controlled and modified. In this work, Sb (0.01 mole (M)) doped CuInS2 thin films are grown in the temperature range 300-400 deg. C on heated glass substrates. It is observed that the film growth temperature, the ion ratio (Cu/In = 1.25) and Sb-doping affects the structural, optical and photoluminescence properties of sprayed CuInS2 films.The XRD patterns confirm that the Sb-doping suppresses the growth of CuInS2 polycrystalline thin films along (1 1 2) preferred plane and in other characteristic planes. The EDAX results confirm the presence of Cu, In, S and Sb. About 60% of light transmission occurs in the wavelength range 350-1100 nm. The absorption coefficient (α) is found to be in the order of 105 cm-1. The band gap energy increases as the temperature increases from 300-400 deg. C (1.35-1.40 eV). SEM photographs depict that large sized crystals of Sb-doped CuInS2 (1 μm) are formed on the surface of the films. Well defined sharp blue and green band emissions are exhibited by Sb-doped CuInS2 thin films. Defects-related photoluminescence emissions are discussed. These Sb-doped CuInS2 thin films are prepared by the cost effective method of spray pyrolysis from the aqueous solutions of CuCl2, InCl3, SC(NH2)2 and SbCl3 on heated glass substrates.