Optical, chemical, electrical, and morphological properties of PEO–Nb-doped KMnO4 thin films

We report on the optical, chemical, and morphological properties of Polyethylene oxide (PEO) with Nb doped with (1%, 2%, 4%, and 8%) of potassium paramagnets (KMnO₄) thin films. The as-prepared PEO–Nb–KMnO₄ thin films are deposited using the casting technique on a glass substrate. The transmittance T% (i) and reflectance R% (λ) of PEO–Nb–KMnO₄ thin films are measured at room temperature in the (250–700) nm spectral range. Interestingly, increasing the doping level of KMnO₄ decreases the transmittance slowly in the low-energy region and abruptly in the high-energy region. Furthermore, a redshift of the absorption edge is observed as the doping level of KMnO4 is increased, implying a significant reduction of the optical bandgap. Index of refraction n and extinction coefficient k for PEO–Nb–KMnO₄ thin film are reported. Furthermore, a combination of classical models, namely, Tauc, Wemple–DiDomenico, and Sellmeier models are employed to measure and interpret the optical behavior, optical bandgaps, dispersion parameters, and optoelectronic parameters of PEO–Nb and PEO–Nb-doped KMnO₄ thin films. The optical bandgap of PEO–Nb is found to be 4.00 eV. Incorporating 8% of KMnO4 into PEO–Nb matrix reduces the optical bandgap to 3.72 eV. To identify the major vibrational modes of the un-doped and doped thin films, Fourier transform infrared spectroscopy (FTIR) analysis is conducted. The major peak at 541 cm⁻¹ of PEO–Nb is associated with the Nb₃–O bond. Introducing KMnO₄ into PEO–Nb matrix leads to remarkable changes of the width, intensity, and the peak positions of the vibrational bands. Electrical properties of the investigated thin films are investigated and elucidated using the four-point probe. The measured conductivity of un-doped PEO–Nb is about\(1.82\times {10}^{-5} S/cm\). Introduction different dopant levels of KMnO₄ boosts the conductivity to \(8.00\times {10}^{-5} S/cm\) at the highest concentration of KMnO₄ (8%). The obtained Scanning Electron Microscopy (SEM) micrographs indicate that the amorphous PEO–Nb thin films exhibit a smooth surface. Inserting different concentrations of KMnO4 yields new aggregations on the constructed surfaces confirming the homogenous distribution of KMnO4 into PEO–Nb matrix. The drastic modifications of optical, chemical, and surface properties of PEO–Nb thin films caused by introducing KMnO4 imply that PEO–Nb–KMnO4 thin films indicate their potential for several optoelectronic applications.