Assessing the Optical Features of Electrodeposited Ti-Doped ZnSe Thin Films for Solar Cell Window Layer Applications

In this article, titanium doped zinc selenide (Ti-ZnSe) thin films have been successfully fabricated onto fluorine doped tin oxide substrate using an electrodeposition method. Zinc acetate, selenium oxide and titanium oxide were used as sources of Zn, Se and Ti ions respectively. The films were characterized for their optical properties using UV-Vis spectrometry technique. The results showed that the absorbance increase as Ti doping concentration increased while transmittance decreased at the affected wavelength ranges. Peak absorbance values in the range of 0.5-0.7 occurred at (250 nm and 350 nm), 0.3 – 0.4 at (600 – 700 nm) and 0.4 – 0.5 at (800 – 900 nm) for the films fabricated with higher concentration of Ti ion source. The films exhibited high refractive index value and increase as Ti concentrations increased with peak values of 2.25 – 3.75 occurring at 250 nm, 4.00 at 350 nm, 2.50 – 2.75 at (600 – 700 nm) and 3.00 – 3.25 (800 – 900 nm) wavelengths. The extinction coefficient of the films is generally low but increase as concentration of Ti increased. The bandgap energies of the deposited thin films are in the order of 3.0 eV, 3.10 eV, 2.70 eV and 2.70 eV for the films deposited with 4ml, 6ml, 8ml and 10ml Ti ions respectively. These bandgaps and other properties of the films are in the range suitable for many device fabrications such solar cell buffer layers and high temperature devices and the trend of the bandgaps are good mainly for photovoltaic cells fabrication for conversion of solar energy to electricity.