Promising naphthol green B dye doped (PVOH-PEG) composite films as a multifunctional material with engineered optical band gap, tunable dielectric properties and nonlinearJ-E characteristics

Polymer composite films of polyvinyl alcohol (PVOH)-polyethylene glycol (PEG)/naphthol green B dye (NGB) were prepared using the solution cast technique with different concentrations of NGB (0-25 wt. (%)). XRD emphasized the semi-crystalline nature of the base polymer blend (PVOH-PEG) which increased by NGB addition. FTIR spectra of the investigated samples confirmed the formation of hydrogen bonds between the polymer blend hydroxyl groups and the NGB molecules. Optical properties are studied within wavelengths ranged from 245 nm to 1500 nm. Multi-optical energy band gaps (E-g) were observed in (PVOH-PEG) doped with NGB dye for the allowed indirect and direct transitions and showed a decrease with the addition of NGB dye. Analysis of the refractive index n offered a normal dispersion within the investigated wavelength region. The dependence of the dielectric constant epsilon', loss epsilon '' and ac conductivity sigma(ac) on frequency (100 Hz-1 MHz) and NGB content were investigated at room temperature (RT). The addition of NGB tends to increase sigma(ac) of the (PVOH-PEG) blend, that serve in various semiconductor devices. The values of the frequency exponent s and the charge carriers binding energy W-M decrease in the presence of NGB dye and are interpreted by the correlated barrier hopping (CBH) model. Electric modulus formalism clarified the presence of a single relaxation peak with a relaxation time tau depends on the NGB wt. (%). The (current density J - electric field E) characteristics were studied at RT and showed a non-ohmic behavior. The current density I increased with the addition of NGB dye and the dc conduction is discussed in view of Schottky-Richardson and Poole-Frenkel theoretical models.