Effect of molar ratio TTIP:Acetylacetone stabilizer on structural and optoelectronics properties of TiO₂ thin films for DSSC solar cell

This work investigates the effect of the molar ratio between the titanium precursor titanium tetraisopropoxide (TTIP) and the stabilizer acetylacetone (Act-ac) on the structural and optoelectronic properties of TiO₂ thin films, prepared by sol-gel for DSSC. Four (4) TiO₂ samples were prepared: one without stabilizer and three others with different TTIP:Act-ac molar ratios of 0.7:1, 0.6:1, and 0.5:1. X-ray diffraction (XRD) analysis revealed a polycrystalline anatase structure with a preferred orientation along the (101) plane. The estimated crystallite sizes ranged from 12.40 to 18.15 nm. Raman spectroscopy confirmed the presence of a pure anatase phase unique in all four samples. The optical properties, analyzed by UV-Visible spectrophotometry confirmed an transparency of the samples in the visible range, between 72% and 80%. The estimated indirect bandgap energies ranged from 3.18 to 3.42 eV. The refractive index of the samples prepared with the acetylacetone stabilizer ranged between 2.204 and 2.554. Electrical properties, assessed by the four-point probe method, revealed a resistivity ranging from 42.897 to 49.882 Ω·cm, and an electrical conductivity between 2.005 × 10⁻² and 2.331 × 10⁻² S·cm⁻¹. The addition of the stabilizer and with the reduction of the TTIP:Act-ac molar ratio improve the structural and optoelectronic properties of TiO₂ thin films. These results demonstrate the significant impact of the Act-ac stabilizer and the TTIP:Act-ac molar ratio on enhancing the properties of pure TiO₂ thin films, intended for use as photoanode in DSSC.