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

• The physical properties of vacuum evaporated CdTe thin films are invesigated.
• The XRD patterns show that the films have zinc-blende structure with cubic phase.
• The optical band gap is found in the range 1.44–1.63 eV and decreased with thickness.
• The electrical conductivity is found to be decreased with film thickness.
• The FESEM image shows that the films are uniform and free from crystal defects.

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.

The physical properties of CdTe films have been investigated and results reveal that films may be used as absorber layer in CdTe/CdS thin film solar cells.Figure optionsDownload as PowerPoint slide