Optical Properties and Analysis of OJL Model’s Electronic inter-band Transition Parameters of TiO2 Films

Abstract

Titanium dioxide is a wide band gap semiconductor responsible for the bright white appearance in most substances. This material has many unique properties due to its extra-ordinary chemical stability. TiO 2 has a conduction band that closely matches the excited energy level of organic dyes hence it is used in fabrication of photo-anode electrode of dye sensitized solar cell. However, the optical properties and the density of states of TiO 2 thin films determine the performance of dye sensitized solar cell fabricated from TiO 2 photo-anode electrode. For this reason, the purpose of this study was to investigate the optical properties and the OJL electronic inter-band transition analysis of TiO 2 nanoparticle thin films. Under the OJL model, the expressions of density of states were specified for the optical transition from the valence band to the conduction band. The TiO 2 nanoparticles were prepared using sol-gel and hydrothermal methods and deposited on a conductive glass substrate by screen printing and spray pyrolysis techniques. SEM analysis revealed that TiO 2 nanoparticles were spongy and had unevenly sphere-shaped profile while TiO 2 nanotubes had a skein-like morphology with abundant number of nanotubes intertwined together. This study showed that TiO 2 thin films have both direct and indirect band-gaps. The OJL Gap energy ( E 0 ) values were observed to be between 30273.2356 and 31072.0000 wavenumbers which translated to band-gap energies between 3.744 and 3.843 eV. From these findings showed that TiO 2 films prepared could be used in the fabrication of high performing dye-sensitized solar cell.