Abstract
Thin films of CdTe semiconductor materials were grown on fluorine doped tin oxide (FTO) conducting glass substrates using the technique of electrodeposition. CdSO 4 at high concentrations and CdCl 2 , TeO 2 at low concentrations were used as precursor salts for electrodeposition. The range of deposition potentials was estimated using cyclic voltammetric measurements. The electrical, optical, structural and morphological characteristics of as-deposited and annealed CdTe thin films were characterized using photo-electrochemical (PEC) cell studies, UV-Vis spectrophotometry, X-ray diffraction (XRD) and scanning electron microscopy (SEM). These particular samples were converted from n-type into p-type after heat treatment. UV-Vis spectrometric measurements for CdTe layers indicated that, the energy band gaps of 1.45±0.02 eV for both as-deposited and annealed samples which exhibited the required optical property for fabricating CdS/CdTe solar cells. Little increase in (220) and (311) peaks of XRD spectra were observed for annealed layers compared to the as-deposited material. However, annealing exhibited a small reduction of cubic phase preferential orientation (111). The optical transmission for both as-deposited and annealed CdTe samples were about 60% for wavelengths longer than about 850 nm.
Highlights
Cadmium telluride (CdTe); a (II-VI) semiconductor material with a direct energy band gap of 1.45 eV possessing a high light absorption coefficient is suitable for efficient solar energy conversion (Chu, et al, 1993)
A mechanism proposed for electrodeposition of CdTe thin films from acidic electrolyte is described below (Engelken, et al, 1985): Cd2+(aq) + 2e
CdTe films were grown by electrodeposition on glass/fluorine doped tin oxide (FTO) substrates using an aqueous solutions containing 1.50 M CdSO4, 1000 ppm CdCl2 and 150 ppm TeO2 at pH 2.00±0.02 and at ~70°C temperature for 5 hour deposition time at a voltage of -650 mV
Summary
Cadmium telluride (CdTe); a (II-VI) semiconductor material with a direct energy band gap of 1.45 eV possessing a high light absorption coefficient is suitable for efficient solar energy conversion (Chu, et al, 1993). Cyclic voltammetry was used to determine the deposition potential range for growing of thin film CdTe materials. Ceylon Journal of Science 45(2) 2016: 53-59 used to obtain (I-V) characteristics, band gaps, crystal types and surface morphologies respectively of the electrodeposited CdTe thin films.
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