Investigation of structural and optical characteristics of PVA/crystal violet dye composites for flexible smart optoelectronic applications

Abstract

Herein, composite films were fabricated using the solution casting route, incorporating different weight percentages of crystal violet (CV) into polyvinyl alcohol (PVA). To examine the final composites, a series of characterization approaches were used. Fourier-transform infrared spectroscopy (FTIR) elucidated PVA/CV molecules’ physicochemical interactions. The analysis through X-ray diffraction (XRD) pointed out a decrease in the semi-crystalline nature of the polymer matrix with a rise in the CV content, thereby enhancing transport mobility and electrical conductivity. The optical properties of PVA influenced by CV dopants were systematically studied in the range of 190–1400 nm. Notably, the PVA/CV composites exhibited improved UV-blocking capabilities in the 190–380 nm range, making them appropriate for uses including UV notch filters and laser hindering filters. An increase in CV doping percentage from 0.1 to 0.8 wt% resulted in a reduction of the indirect optical bandgap of PVA from 5.16 ± 0.013 eV to 4.77 ± 0.069 eV. Additionally, the Wemple-DiDomenico model revealed significant enhancements in the optical parameters. Specifically, the dispersion energy and oscillator energy of PVA/CV composites increased from 0.91 eV and 2.01 eV to 6.83 eV and 3.25 eV, respectively, along with an increase in the lattice dielectric constant (ε_L) from 1.71 to 3.47. These improvements in dispersion factors were attributed to the cross-linking of CV with the polymer matrix. Furthermore, the composite films demonstrated notable nonlinear optical properties, indicating their potential for practical applications in photonic and optoelectronic devices.