Design of PVA based nanocomposite via tungsten trioxide Nanoparticles incorporation with low thermal emissivity and enhanced optical parameters

Abstract Poly (vinyl alcohol) (PVA) is a flexible and chemically durable polymer. However, the broad optical band gap and the insulating nature of PVA restrict its employment in sophisticated optoelectronic devices. In the present study, the solvent casting approach has been effectively used to manufacture eco-friendly PVA/WO₃ nanocomposite films comprising 0–7 wt.% of hydrothermally generated monoclinic WO₃ nanoparticles. X-ray diffraction and ATR-FTIR analyses verified the strong intermolecular hydrogen bonding between PVA and WO₃ that resulted in the decreased crystallinity and improved amorphous character of the polymer matrix. The surface morphology exhibited a more homogenous and interconnected distribution of the filler with increased WO₃ loading. Optical investigation indicated a large drop in the optical band gap from 5.25 eV for pure PVA to 2.65 eV for the 7 wt% WO₃ nanocomposite and an increase in the Urbach energy from 0.202 eV to 0.589 eV, which implies the generation of localized states inside the band gap. With increasing WO₃ content, a change from direct authorized to direct banned electronic transfer was observed. Also, the refractive index, dielectric constant, and free charge carrier concentration to effective mass ratio (N/m*) were enhanced from 12.76 × 10 55 to 281.63 × 10 55 m 3 kg − 1 , while the sheet resistance dropped substantially. The thermal emissivity was lowered to around 10 − 9 , exhibiting very good low-emissivity features. These results suggest that WO₃ is a good nanofiller for tuning the structural, optical, dielectric, and electrical properties of PVA, and the prepared nanocomposites are promising materials for flexible optoelectronic devices, solid polymer electrolytes, low-emissivity coatings, and energy-efficient smart window applications.