Tailoring the physical properties of titania thin films with post deposition air and vacuum annealing

Abstract The present article carefully reports the influence of post deposition annealing on photophysical properties of titania (TiO2) thin films, which are developed employing the electron-beam deposition technique. The pristine films are annealed at 100 °C, 200 °C, 300 °C in air and vacuum conditions followed by the investigation of photophysical properties employing several characterization tools viz. XRD, SEM, AFM, EDS, PL, UV Vis. spectrophotometer and source meter. The films showed amorphous nature, whereas Ti and O peaks in the EDS pattern are evident for TiO2 films deposition. The increase in annealing temperature resulted into an increment in the transmittance (except for 100 °C) of air annealed films, whereas transmittance is decreased for vacuum annealed films. The obtained higher transmittance is suitable for TiO2 thin films to implicate as buffer layer for solar cell devices where the band gap is observed in a range of 3.06–3.13 eV for air annealed and 2.57–3.05 eV for vacuum annealed films. The electrical conductance of films is enhanced up to 200 °C during annealing possibly due to the removal of traps present in titania thin films. AFM analysis of air annealed films demonstrates a decrement in surface roughness and grain size. Room temperature photoluminescence spectra exhibited strong peaks at 400 nm and 621 nm corresponding to the band edge and Ti2+, Ti3+, Ti4+ surface state emissions, respectively. The higher transmittance, lower surface roughness, and ohmic nature of 300 °C air annealed films might attract kind attention for photoanode and optical window or buffer layer applications in dye-sensitized and Cd-based solar cells and charge transport layers in organic and perovskite solar cells.