Assessment of thermal annealing on structural, electrical, optical and surface topographical features of titania films for solar cells

Titanium dioxide or titania has profoundly attracted the academia and industries due to its unique physical and chemical characteristics and diverse applications from solar cells to photocatalysts. The titania thin films have different roles in CdTe, perovskite, dye sensitized and organic solar cells as window/buffer layer, electron transport layer, photoelectrode etc. In order to further improve the stability and performance of these solar cells, tailoring the properties of titania films is essential which could be done by thermal annealing. The present work meticulously reports an assessment on thermal annealing induced structural, electrical, optical and topographical features of e-beam evaporated titania films which are annealed in temperature range of 100-500 degrees C for 1 h. The XRD analysis reveals phase transformation from amorphous to crystalline nature with annealing at 400 degrees C and 500 degrees C temperature. The electrical measurements unveil the Ohmic nature and increment in resistivity for annealed films vis-a-vis the pristine. Optical properties indicate high transparency for all the films where the optical energy band gap lies in range of 3.53-3.69 eV. Surface topographical study demonstrates changes in average and RMS roughness of films with annealing treatment. The assessment shows that titania films annealed at 500 degrees C exhibited crystalline nature with improved crystallinity, higher transmittance in visible region, suitable optical energy band gap and Ohmic nature, thus, these could be recommended for optical window and electron transport layer applications to the associated solar cell devices.