Controlling the dielectric and optical properties of polyvinyl alcohol/polyethylene glycol blends by adding copper oxide nanoparticles for application in energy storage devices

Copper oxide nanoparticles (CuONPs) were prepared using the sol–gel technique. Polyvinyl alcohol/polyethylene glycol (PVA/PEG) blend filled with different concentration of CuONPs were synthesized using the solution casting way. TEM micrograph indicated the polydisperse and quasi-spherical shapes of CuONPs with an average size of 21.4 nm. FT-IR measurement showed that the intensity of the spectra reduced with increasing concentration of CuONPs. XRD study showed that PVA/PEG blend had a semi-crystalline structure; adding CuONPs decreased the crystallinity degree, revealing the proper intercalation of CuO nanoparticles within PVA/PEG polymeric system. UV/vis analysis indicated that the addition of CuONPs resulted in improved optical absorption and narrowed the allowed direct/indirect optical gap of the polymeric samples. Using frequency-dependent AC conductivity and electrical modulus, the dynamic ionic activity and the type of relaxation process of electrolytes samples were studied. The dielectric constant (ε′) and dielectric loss (ε′′) increase with concentrations of CuONPs in the low-frequency part, indicating the effects of space charge polarization. The impedance parameters were analyzed using a Nyquist diagram, which showed a single semicircle for all samples whose radius of curvature reduced with increasing the nanofiller loading, as well as the appearance of inclined spike for the two samples with the highest concentration of CuONPs. These parameters can be best fitted to two models of equivalent circuits. The obtained results confirm that these PVA/PEG/CuO nanocomposites are candidates for optoelectronic applications, thin film capacitors, energy storage, and flexible nanoelectrics for frequency-operated microelectronic devices.