Effect of Solution Concentrations on the Structural, Morphological, Optical, and Electrical Properties of SnO2:F Thin Films Prepared by Spray Pyrolysis Method

Fluorine-doped tin dioxide (SnO₂:F) films were deposited onto glass substrates using a facile spray pyrolysis method. The effect of solution concentrations on the structural, morphological and optical properties of SnO₂:F films is investigated using various characterization studies. All films exhibited tetragonal rutile structures with a preferred orientation in the (110) plane, which changes to the (211) plane gradually with increasing solution concentration. The average crystallite size of SnO₂:F films decreased as the solution concentration increased, ranging from 40.29 to 38.05 nm. Atomic Force Microscopy (AFM) analyses revealed a marked improvement in grain distribution with increasing solution concentration, accompanied by a corresponding enhancement in surface pressure and decreased roughness. All the regions, produced samples exhibited high transparency from 70 to 82%. The SnO₂:F (0.4 mol/L) film has the best transparency (≈82%). The band gap values of SnO₂:F films with different solution concentrations (0.2, 0.3, and 0.4 mol/L) are 3.84, 3.93 and 3.97 eV respectively, with a high band gap of 3.97 eV for the SnO₂:F (0.4 mol/L) films. Hot probe studies reveal that all films exhibit n-type conductivity. The lowest resistivity of 8.4 × 10^–4 Ohm cm was found for films deposited at 0.4 mol/L. The figure of merit (\({{\phi }_{{{\text{TC}}}}}\)) of SnO₂:F thin films revealed a maximum value of about 9.757 × 10^–3 Ohm^–1 at the wavelength of 500 nm. These results suggest that SnO₂:F films fabricated by spray pyrolysis can be considered effective candidates for integration into optoelectronic devices, particularly as transparent conductive layers in photovoltaic applications.