Tunability of conductivity type and energy band gap of CdTe thin film in the electrodeposition technique

Abstract

In this research, cadmium telluride (CdTe) thin films were fabricated using electrodeposition technique at 1400 mV cathodic potential. CdTe films were deposited on fluorine doped tin oxide (FTO) substrate of dimension 2.3 by 2.4 cm2 at varied time of deposition. X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet visible spectrophotometer (UV-vs), photoelectrochemical cell measurement (PEC), and energy dispersive X-ray spectroscopy (EDX) were used to characterize the structural, morphological, optical, electrical conductivity and elemental composition of electrodeposited films respectively. The particle average crystallite size was estimated as 11.98 nm. The energy band gap of as deposited films decreases as the period of deposition increases for both annealed and unannealed samples. Furthermore, the period of deposition was found to constitute major factor in the dominance of the constituent elements, thereby influencing the electrical conductivity and band gap properties of the films. Consequently, the conductivity of CdTe can be reasonably tuned when heat-treated and the tunability of the energy band gap can be achieved by varying the period of deposition in the electrodeposition technique. Despite the potential of electrodeposited CdTe in solar cells applications, synthesis of p-type CdTe in a stable way place a bottleneck to the utilization of CdTe as a good absorber layer in preventing front surface recombination when CdTe form a heterojunction with any window layer material.