SnO₂ thin films were prepared using a dip-coating sol–gel process on the glass substrates with different precursor molar concentrations (0.3, 0.6, 0.8 and 1 M). X-ray diffraction (XRD) analysis showed that all samples are polycrystalline and crystallize in a tetragonal rutile structure. With the increase of the molarity, the crystallite size increased. The molarity strongly dictates the film texture, with clear changes in the preferred growth orientation (quantified by \({\text{TC}}_{\text{hkl}})\) .UV–visible optical measurements indicated that all films are highly transparent (∼ 84–87% in the visible region) upon annealing at 500 °C. The optical band gap exhibited an apparent blue shift up to a concentration of 0.6 M, reaching a value of 3.82 eV, followed by a slight decrease at higher concentrations. It is noteworthy that a minimum refractive index of 2.133 was also observed at the same concentration. AFM analysis shows that the 0.6 M film presents the lowest surface roughness, a condition that correlates with the maximum band gap and reduced light scattering at low molarities transmittance. Room temperature photoluminescence studies showed broad UV emission with intensity being dependent on the molarity of the precursors. Hall Effect measurement revealed an n-type conduction for all samples. Among them, the 0.6 M-prepared film showed the lowest resistivity (0.186 Ω·cm), the highest conductivity (5.56 (Ω·cm) ⁻1) and the best figure of merit (4.9 × 10⁻5Ω⁻1). Finally, The 0.6 M film has been identified as a sweet spot that compromises on nanostructures, wide bandgap, high transparency, and excellent optoelectronic performances, rendering it a promising candidate for transparent electronics and optoelectronics.
