This paper presents the influence of thickness on physical properties of polycrystalline CdTe thin films. The thin films of thickness 450 nm, 650 nm and 850 nm were deposited employing thermal vacuum evaporation technique on glass and indium tin oxide (ITO) coated glass substrates. The physical properties of these as-grown thin films were investigated employing the X-ray diffraction (XRD), source meter, UV-Vis spectrophotometer, scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The structural analysis reveals that the films have zinc-blende cubic structure and polycrystalline in nature with preferred orientation (111). The structural parameters like lattice constant, interplanar spacing, grain size, strain, dislocation density and number of crystallites per unit area are calculated. The average grain size and optical band gap are found in the range 15.16–21.22 nm and 1.44–1.63 eV respectively and observed to decrease with thickness. The current-voltage characteristics show that the electrical conductivity is observed to decrease with thickness. The surface morphology shows that films are free from crystal defects like pin holes and voids as well as homogeneous and uniform. The EDS patterns show the presence of cadmium and tellurium elements in the as grown films. The experimental results reveal that the film thickness plays significant role on the physical properties of as-grown CdTe thin films and higher thickness may be used as absorber layer to solar cells applications.

Influence of thickness on physical properties of vacuum evaporated polycrystalline CdTe thin films for solar cell applications

The thickness and physical properties of electron beam vacuum evaporated CdZnTe thin films have been optimized in the present work. The films of thickness 300 nm and 400 nm were deposited on ITO coated glass substrates and subjected to different characterization tools like X-ray diffraction (XRD), UV‐Vis spectrophotometer, source meter and scanning electron microscopy (SEM) to investigate the structural, optical, electrical and surface morphological properties respectively. The XRD results show that the as-deposited CdZnTe thin films have zinc blende cubic structure and polycrystalline in nature with preferred orientation (111). Different structural parameters are also evaluated and discussed. The optical study reveals that the optical transition is found to be direct and energy band gap is decreased for higher thickness. The transmittance is found to increase with thickness and red shift observed which is suitable for CdZnTe films as an absorber layer in tandem solar cells. The current-voltage characteristics of deposited films show linear behavior in both forward and reverse directions as well as the conductivity is increased for higher film thickness. The SEM studies show that the as-deposited CdZnTe thin films are found to be homogeneous, uniform, small circle-shaped grains and free from crystal defects. The experimental results confirm that the film thickness plays an important role to optimize the physical properties of CdZnTe thin films for tandem solar cell applications as an absorber layer.

Effect of thickness on physical properties of electron beam vacuum evaporated CdZnTe thin films for tandem solar cells

Thermal annealing induced physical properties of electron beam vacuum evaporated CdZnTe thin films

Electrical, structural and optical properties of Cd 1-x Zn x Te thick polycrystalline films

Enhanced structural, electrical and optical properties of evaporated CdZnTe thin films deposited on different substrates

High quality polycrystalline CdZnTe films were prepared by aluminum induced crystallization (AIC) and radio frequency (r.f.) magnetron sputtering. The crystallinity, morphology and optical property of both as-deposited and AIC samples were investigated by X-ray diffraction (XRD), and atomic force microscopy (AFM), as well as Raman and ultraviolet–visible spectrometry. The results of XRD showed that AIC favours the preferential orientation [1 1 1], and promotes the crystallinity of the CdZnTe films. AFM micrographs show that the grain size was increased from 50 nm to 300 nm after AIC. In the Raman spectrum of CdZnTe films, the intensity of CdTe-like TO mode is enhanced after AIC. From the optical transmittance and absorption coefficient, the value of the band gap varied from 1.53 eV to 1.65 eV.

Effect of Al-induced crystallization on CdZnTe thin films deposited by radio frequency magnetron sputtering

The present invention relates to a preparation method for a metal aluminum induced polycrystalline cadmium zinc telluride film. The preparation method is characterized by comprising: cleaning a substrate; then under a vacuum degree condition, heating, introducing argon gas, and carrying out backwash cleaning; applying a sputtering power on a cadmium zinc telluride crystal target to carry out build-up of luminance; plating a cadmium zinc telluride forerunner film on the surface of the substrate; then sputtering a metal aluminum film on the surface of the cadmium zinc telluride forerunner film to prepare a cadmium zinc telluride forerunner film/induced metal Al film laminated structure; under a protection atmosphere of argon gas, carrying out a heat treatment on the cadmium zinc telluride forerunner film/induced metal Al film laminated structure; and finally adopting a sodium hydroxide solution with a pH value of 12 to remove aluminum material corrosion precipitated from the surface to obtain the polycrystalline cadmium zinc telluride film product. The method has advantages and effects of low cost, application for large area film deposition, high adhesion between the film and the substrate, good controllability, high raw material utilization rate, high production efficiency, good formed film quality, large grain size, and high carrier mobility.

Pan Songhai

Papers

Effect of Al-induced crystallization on CdZnTe thin films deposited by radio frequency magnetron sputtering

Preparation method for metal aluminum induced polycrystalline cadmium zinc telluride film