Cu doping effect on optical, structural and morphological properties of Cd0.9Zn0.1S thin films

Abstract

Undoped and Cu doped Cd0.9Zn0.1S thin films have been prepared on glass substrate by chemical bath deposition technique for different Cu concentrations from 0.01 to 0.04 at 80°C. Crystalline phases and optical absorption of the films have been studied by X-ray diffraction and UV–visible spectrophotometer. Elemental composition was studied by the energy dispersive X-ray (EDX) analysis and the microstructure was examined by scanning electron microscope. The average crystalline size of the films was calculated from X-ray line broadening and it is decreased from 3.2 to 1.6nm for x=0–0.04 which was confirmed by SEM studies. Energy band gap was calculated from optical studies and is varied from 2.41 to 2.45eV where Cu=0.02 has a minimum value as 2.41eV. The observed lower crystalline size (1.6nm) and higher energy gap (2.45eV) in Cd0.86Zn0.1Cu0.04S thin film is useful to design a suitable window material in fabrication for solar cells. The existence of functional groups and chemical bonding were confirmed by FTIR studies. The observed blue shift of both blue band (from 413 to 407nm) and green band (from 538 to 523nm) in photoluminescence spectra with enhanced intensity confirmed the substitution of Cu into Cd–Zn–S lattice.