Complex optical studies on a semiconducting derivative of polyindole as-synthesized through a chemical route

Semiconducting polymers have become a significant area of research, as their electrical and electrochemical properties suggest a wide range of potential applications, including transistors, Schottky diodes, light-emitting diodes, and rechargeable batteries. This study aims to explore the novel optical characteristics of as-synthesized semiconducting poly(2-amino-5-(1H-indolyl)-5H-thiazolo[4,3-b]-1,3,4-thiadiazole) (PAITTD) and its N-substituted indole derivatives, which include a side chain containing chlorobenzene (PACBITTD) and bromobenzene (PABBSITTD). Several optical parameters, including the refractive index n(λ), optical conductivity (σ _opt ), extinction coefficient (k), dissipation factor (tan δ), and relaxation time (τ) are calculated from the absorpance spectrum A(λ) recorded in the range of 200 to 1200 nm. The synthesized polymer samples demonstrated absorption in the range of 250 to 1000 nm. The absorption spectra are analyzed using multiple peak analysis techniques. The evaluated optical gaps (E _g = 1.53-2.05 eV) are confirmed through various methods. It calculated from the intersections of the linear plot (αh ν ) ² with the h ν -axis, the extrapolation of the straight line of the e' and e" curves of the dielectric constant to the abscissa-axis (photon energy), the intercept of the dielectric relaxation time and hν and the cross-point between the curves of σ _opt and σ _e . Notably, the optimized polyindole derivatives exhibited a reduced optical band gap of 1.53 eV in the visible region. This estimated optical band gap indicates that these materials have considerable potential for applications in photocatalysts and optoelectronic devices.