DOI: https://doi.org/10.55373/mjchem.v28i3.274

Keywords: Polycarbazole, SnO₂ nanocomposites, TiO₂ nanocomposites, optical band gap, photoluminescence quenching

Abstract

This study explores the optical properties of Polycarbazole (PCz) polymer nanocomposites incorporating tin oxide (SnO₂) and titanium oxide (TiO₂) nanofillers. The influence of nanofiller content on the optical characteristics, including absorption and photoluminescence (PL) behavior, was systematically examined. UV-Vis absorption spectra show that the absorption edge of the nanocomposites shifts to longer wavelengths (red shift) as the concentration of SnO₂ and TiO₂ increases. This shift is attributed to the formation of defect-related energy states and changes in the polymer's conjugation length due to interactions between the polymer chains and nanofillers. Tauc plot analysis was used to estimate the direct and indirect optical band gaps of the nanocomposites. It was observed that both direct and indirect band gaps decrease with increasing nanofiller content. For PCz/SnO₂, the direct band gap reduces from 3.93 eV (pure PCz) to 3.84 eV with 20% SnO₂, while for PCz/TiO₂, the direct band gap decreases from 3.93 eV to 3.81 eV. These decreases are attributed to the modification of the polymer's electronic structure and the creation of defect-related energy levels within the band gap. Photoluminescence spectra reveal a shift in emission peaks to longer wavelengths and a decrease in fluorescence intensity, indicating quenching effects due to the strong interaction between the polymer and the nanofiller. Fluorescence decay measurements show a decrease in carrier lifetime with increasing nanofiller concentration, supporting the hypothesis of enhanced charge transfer and dynamic quenching. These findings highlight the potential of PCz/SnO₂ and PCz/TiO₂ nanocomposites for applications in optoelectronics and photonics.