Electrodeposition of CdTe thin films using an acetate precursor for solar energy application: The effect of deposition voltage

Abstract

Cadmium Telluride (CdTe) thin films were synthesized using a low-cost two-electrode electrodeposition configuration in potentiostatic mode and from an aqueous acidic solution. More commonly used cadmium salts for electrodeposition of CdTe include CdSO4, CdCl2 and Cd (NO3)2. In the present work, a less commonly used salt, cadmium acetate, was used as a cadmium precursor for the growth of CdTe thin films. The thin films were deposited on a coated glass fluorine- doped tin oxide (FTO) substrates. The deposition voltage was varied from 1230 to 1270 mV with a 10 mV increment. The structure, optical, conductivity, surface morphological, elemental composition, and surface roughness properties of the as-deposited thin films were investigated by using X-ray diffraction (XRD), UV–VIS spectrophotometry, Photoelectrochemical cell analysis (PEC), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and scanning probe microscopy (SPM), respectively. The XRD results showed that the CdTe thin films displayed a higher intensity at 1250 mV deposition voltage. UV–VIS spectroscopy measurements revealed that the band gap of the CdTe thin films was near that of the bulk CdTe at 1250 mV deposition voltage. The PEC measurement indicated that at a low voltage of 1230 mV, the conductivity of the film was p-type and Te-rich. When the deposition voltage was 1270 mV, the CdTe films became n-type and Cd-rich. EDS results confirmed the presence of both Cd and Te with more stoichiometric values at the growth voltage of 1250 mV. The SEM images showed that the surface morphology changed with deposition voltage. SPM results indicated that the highest average surface roughness value of 94.9 nm was obtained with a deposition voltage of 1250 mV. These results indicate that the film prepared at a deposition voltage of 1250 mV, may have better potential application as an absorber layer in solar cell device.