Tailoring the properties of nebulizer spray pyrolysis coated FTO thin films through rare earth element terbium for optoelectronic applications

In optoelectronic device, transparent conducting oxide (TCO) acts as an electrode. In this work the rare earth element terbium (Tb) was doped with FTO by simple and inexpensive nebulizer spray pyrolysis (NSP) technique. Structural, optical end electrical properties were investigated for all the synthesized films. X-Ray diffraction (XRD) analysis confirmed that all the prepared films exhibited polycrystalline nature with tetragonal crystal structure and size of the crystalline reduced with increasing Tb concentration. Raman active doubly degenerate mode (E_g), IR active mode (E_u) and vibration mode (B_2g) were found from Raman analysis. Atomic force microscope (AFM) images visualises the granular sized particle and the roughness of the Tb doped films. Elememental analysis spectrum exhibited Sn, O, F and Tb elements for 1.5 wt.% Tb doped thin film. Photoluminacence (PL) analysis revealed that UV, blue and green (visible) emission and UV emission intensity was reduced systamatically for the doped films. From UV–Vis analysis, highest optical transmittace were deduced for 1.5 wt.% Tb doped film. Reflectance, absorbance and band gap also been observed for the prepared films. Refractive index, extinction coefficient and dielectric constant values were decreased with increasing Tb doping concentration. High electrical conductivity and carrier concentration were measured using four probe hall effect system. Figure of merit value for the 1.5 wt.% Tb doped film is 1.5 × 10⁻³ Ω^-1 and therefore the prepared film suits to be an electrode in optoelectronic devices.