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

Semiconducting polymers, especially polyindole, have become a significant area of research due to their superior electrical, optical, and electrochemical properties. These properties qualify it for a wide range of potential applications, including transistors, Schottky diodes, light-emitting diodes, and rechargeable batteries. 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), have been prepared by the radical polymerization process. Characterization techniques, such as XRD, SEM, and TGA/DSC, have been employed to investigate the structural, morphological, and thermal properties of the prepared compounds. The optical properties were investigated by measuring absorbance using a UV-visible spectrophotometer in the range of 200–1200 nm. Several optical parameters, including the refractive index n(λ), optical conductivity (σopt), extinction coefficient (k), dissipation factor (tan δ), and relaxation time (τ), are calculated from the absorpance spectrum A(λ). A PAITTD and PACBSITTD depict three semi-sharp absorption peaks at (212 -352- 412 nm) and (212–478–700 nm), respectively. These three absorption peaks of PAITTD increase to five (212–352 – 412–498–700 nm) for PABBITTID. The absorption spectra are analyzed using multiple peak analysis techniques. The lowest evaluated optical gaps for PACBSITTD (Eg = 1.53–2.05 ± 0.05 eV) are confirmed through various methods. First, it was calculated from the intersections of the linear plot (αh ν ) ² with the h ν -axis. Second, it was determined from the extrapolation of the straight line of the ε’ and ε” curves to the h ν -axis. Third, the intercept of the dielectric relaxation time with hν was used as a disjunctive method. Finally, it was ascertained from the cross-point between the curves of σ _opt and σ _e . PACBITTD, with the lowest band gap, broad spectral coverage and high photon harvesting efficiency, is a very promising material for solar cells, photodiodes, and other cutting-edge light-harvesting technologies.