Structural and optical properties of CdTe thin films obtained by electrodeposition

Abstract

Thin films of CdTe have been obtained by electrodeposition in the presence of tartaric acid on fluorine-doped tin oxide (FTO)-coated glass substrates, under a constant voltage of 1.40 V. In order to determine the deposition parameters of CdTe, cyclic voltammetry has been performed. The films were annealed at Т= 200 oС, Т= 300oС, Т= 400oС and Т= 450oС, in air atmosphere. The X-ray diffractograms show that the films obtained at 90oC are nanocrystal with cubic structure and with grain size of 6 nm. The thermal treatment of CdTe films contributes to grain growth and obtaining polycrystalline films. Atomic Force Microscope shows that the films are smooth and uniform with columnar grains. The optical properties of the CdTe films have been investigated by measurements of wavelength-dependent transmission. The optical band gap of as-deposited films is 1.48 eV and is decreasing up to 1.45 eV, for films annealed at temperature of 300оС, and increasing again at temperature of 450оС. Lastly, SnO2-CdS-CdTe-electrolyte-graphite type photoelectrochemical solar cells have been made, using the 0.1 М NaOH-Na2Sx electrolyte. From the measured current-voltage characteristics, open circuit voltage of Voc= 500 mV and short circuit current of Isc= 1.2 mA/cm2 have been determined.