Comprehensive evaluation of the impact of ionic liquid incorporation on the optical properties, Urbach energy, thin film morphology, and surface roughness of poly(vinyl chloride) based on ionic materials

A newly synthesis composite thin films of poly(vinyl chloride) has been refinement with ionic liquid, where PVC dissolved in THF with various concentrations of IL by casting method to form the composite thin films, without any reaction and IL dangles within PVC matrix. The thin films were examined by the diffusive reflectance device under the wavelength range (238-1300 nm). The XRD, EDX, and AFM techniques were utilized to discover the structure of the PVC matrix after additive IL. The XRD analysis illustrated the amorphous structure of the films, while the EDS analysis illustrated the main composition of pure PVC and composite PVC/IL. The optical properties and optical parameters were studied. The reflectance, extinction factor, transmittance, and imaginary dielectric constant declined, the absorption value was between (80-89 %), and the refractive index, real dielectric constant, and optical conductivity were increased. The indirect energy gap declined from 4.2 eV to 2.2 eV and the direct energy gap declined from 3.7 eV to 2.6 eV. The Urbach energy was increased from 2.09 eV to 15.45 eV revealing an increase in the disorders of electrons. The E_d increased from 23.42 eV to 70.68 eV and E_o increased from 7.00 eV to 10.88 eV. AFM analysis illustrated the roughness of the films increased after additive IL to the PVC Matrix from 1.08 nm to 4.45 nm and the root mean square of the particles ranged from 1.57 nm to 5.56 nm. The PVC composite thin films are utilized in solar cell and sodium-ion battery applications.