The effect of growth voltage on the structure, electrical and optical properties of CdTe thin films prepared by electrodeposition method

A.U Yimamu; M.A Afrassa; B.F Dejene; K.G Tshabalala; S.Z Werta; J.J Terblans; H.C Swart; S.J Motloung

Authors

A.U Yimamu Department of Physics, University of the Free State, Bloemfontein/QwaQwa Campus, South Africa and Department of Physics, Adama Science and Technology University, Adama, Ethiopia
M.A Afrassa Department of Physics, Adama Science and Technology University, Adama, Ethiopia
B.F Dejene Department of Physics, Walter Sisulu University (Mthatha), Mthatha, South Africa
K.G Tshabalala Department of Physics, University of the Free State, Bloemfontein/QwaQwa Campus, South Africa
S.Z Werta Department of Physics, College of Natural and Computational Sciences, Dire Dawa University, Dire Dawa, Ethiopia
J.J Terblans Department of Physics, University of the Free State, Bloemfontein/QwaQwa Campus, South Africa
H.C Swart Department of Physics, University of the Free State, Bloemfontein/QwaQwa Campus, South Africa
S.J Motloung Department of Physics, University of the Free State, Bloemfontein/QwaQwa Campus, South Africa

Keywords:

Electrodeposition, Thin film, CdTe, Two electrodes, deposition voltage, electrolytic solution

Abstract

Cadmium Telluride (CdTe) thin films were grown using a low-cost two-electrode electrodeposition method in an aqueous acidic solution. The solution contained 1 M of cadmium acetate dihydrate (Cd (CH3OO)2. 2H2O) as cadmium precursor and 2 ml of tellurium dioxide (TeO2) as tellurium precursor. The thin films were deposited on coated glass florin doped tin oxide (FTO) substrate with a sheet resistance of 8 ohm/square. The deposition voltage was varied from 1200 to 1450 mV with a 50 mV increment to investigate the range of deposition voltage. The X-ray diffraction (XRD) results show that CdTe thin films were polycrystalline cubic zinc blend structures, and the best crystallinity was observed at deposition voltage of 1250 mV with crystallite size of 26 nm. Ultraviolet-visible (UV-VIS) measurements revealed that the maximum absorbance was recorded at 1250 mV, and the energy band gap of CdTe thin films varies from (1.46 to 2.02) eV. At the voltage of 1250 mV, the band gap was 1.46, which is near the bulk energy band gap of CdTe (1.45 eV). Photoelectrochemical cell (PEC) measurement confirmed that the conductivity of CdTe varies with deposition voltage. It has exhibited a p-type conductivity due to Te-rich CdTe at low voltage and becomes n- type Cd-rich CdTe film at high voltage.