Optical Band Energy, Urbach Energy and Associated Band Tails of Nano Crystalline TiO<sub>2</sub> Films at Different Annealing Rates

Increase in world population has led to more energy demand. Therefore, there is need for utilization of green and renewable energy. Dye sensitized solar cells (DSSCs) based on TiO2 have attracted a lot attention as an alternative source compared current silicon technology. In this study, thin films were deposited doped fluorine tin oxide layer (FTO) glass substrates using sol-gel doctor blading technique. The annealed at different rates (1step, 2°C/min 1°C/min) up temperature 450°C followed by sintering 30 minutes. UV-VIS spectrophotometry was employed probe the absorbance reflectance films. It found that, optical parameters, such reflectance, real (ε1) imaginary (ε2) parts dielectric constant, skin depth, Urbach gap; all depend annealing rate. depth samples visible region increase from 6.319 x 10-5 11.968 cm-1 due annealing. Optical band (Eg) decreased 5.04eV film 4.35eV rate 1°C/min direct allowed 2.76 2.56 eV indirect transitions. tails weak absorption with energies (Eu) range 432-505 meV This used account disorder An inverse relation between result reported.