Physical characteristics of polymer composites based on PVA doped with Mn2+ metal complexes synthesized by green approach: insights to linear and optoelectronic optical properties

In the current work, a novel methodology based on the green approach has been carried out to prepare polymer composites with declined optical band gap. The extracted dye of black tea was used to create Mn2+ metal complexes. The XRD outcomes establish that Mn2+ complexes disrupt the hydrogen bonding between polyvinyl alcohol (PVA) chains. The FTIR results confirm the occurrence of interactions among the components of PVA composites. The UV-visible spectroscopy study was carried out to measure the fundamental optical and optoelectronic parameters, including absorption edge, refractive index (n), dielectric loss (epsilon(i)), band gap energy (E-g), phase velocity, grouped velocity, sheet resistance (R-s), and thermal emissivity (epsilon(th)) of the pure PVA and composite films. The results showed that the doped PVA exhibits a band gap of 1.62 eV. Furthermore, Tauc's method was implemented to determine the possible types of electronic transitions. The ASF method was examined as an alternative to Tauc's approach to determine the E-g values. Increasing in band tail from 0.269 to 0.362 eV indicates a remarkable presence of disorder phases in composite films. The W-D model was used to evaluate the oscillator energy E-0. From Taucs model it was found that the optical band gap declines from 5.893 eV for pure PVA to 1.849 eV for PVA composites. The refractive index of PVA polymer was found to improve for PVA inserted with Mn-metal complexes. The results establish that polymer metal complexes are more efficient in increasing light-matter interactions.