Effect Of Annealing Temperature On The Optical And Structural Properties Of Zinc-Doped Cd2SnO4 Thin Films Prepared By Dip-Coating Method

As demand for solar PV modules steadily increases studies on cheaper alternative TCO materials, with low resistivity and high transmittances in the visible spectrum to replace ITO are been undertaken. Among TCO materials considered as alternative to Indium Tin Oxide (ITO) is Cd2SnO4, owing to its availability in large quantities at relatively lower costs. Studies on optical properties of N2 and F2 doped Cd2SnO4 films have revealed increased transmittance 99%, and reduced band gap 3.3 eV. On the other hand Fe doped films have been observed to exhibit higher refractive indices, extinction and absorption coefficients with lower transmittance and optical band gap. Although studies have been carried out on Zinc doped Cd2SnO4 films, the effect of annealing temperature on the properties of the films have not been reported. This study investigated the effect of annealing temperature on the optical and structural properties of Zinc-doped Cd2SnO4 films. Thin films of Zincdoped Cd2SnO4 were prepared by mixing 0.1 M Cadmium Acetate with 0.1 M Tin II Chloride in ratio 1:1 to prepare Cd2SnO4 which was doped with 0.1 M Zinc Nitrate then dip-coated on clean glass substrates. The coated substrates were dried at room temperature and annealed in air the films annealed at 350 o C, 400 o C and 450 o C for 90 minutes Optical transmittance and reflectance were measured in wavelength range 200-1200 nm and with the results: prominent XRD peak oriented in the (2 0 0) direction, transmittance of 78.7% at 700 nm wavelength, absorption coefficient of 3.891 - 5.591 x 104 cm-1 , extinction coefficient of 0.1852 - 0.2126, refractive indices of 1.983-2.121 at 588 nm wavelength and band gap values range 3.45-3.65 eV. Annealing was observed to reduce refractive index and does not affect transmittance therefore doesn’t enhance suitability of films as TCO materials for Photovoltaic applications.