Design of a smart optical sensor employing Toluidine Blue dye as an effective laser optical limiter integrated into (PVA) composite films: Electrical conductivity and dielectric characteristics improvement

Abstract

Poly(vinyl alcohol), PVA doped with (0, 0.11, 0.55, 1.11, and 5.5) wt% of Toluidine Blue dye (TB dye) was prepared by the traditional casting method. The influence of Toluidine Blue dye concentration on spectroscopic, optical, and dialectical properties was investigated. Fourier transform infrared (FTIR) spectroscopies and X-ray diffraction were used to study the molecular and crystalline structure of PVA/Toluidine Blue dye composites. A UV–Visible spectrophotometer was used to investigate the optical characteristics. For all samples, the full-width half-maximum absorption spectra were determined. The direct and indirect allowed transitions have a multi-graded bandgap structure. Within the frequency range of 3 kHz to 10 MHz, the dielectric constant (ε′) and dielectric loss (ε″) were investigated and found to be dependent on the weight percent of TB dye. The correlated barrier hopping can describe the conduction mechanism for the studied samples. Furthermore, the PVA/5.5 wt% TB film demonstrated excellent optical CUT-OFF properties with a low transmission value in the spectral range (200–1300 nm), which is a favorable result for the fabrication of long-blocking optical filters and protective windows for optoelectronic and photonic devices like organic/polymer light-emitting devices, dye-sensitized solar cells, optical limiters, and optical switches.