Modulation of Structural, Optical and Electrical Properties of Polyaniline Through SnO ₂ Incorporation: A Synergistic Experimental and Density Functional Study

ABSTRACT Polyaniline (PANI) and tin oxide (SnO ₂ ) doped polyaniline (PANI/SnO ₂ ) composites were prepared using an in situ chemical polymerization route. The existence of sharp peaks of SnO ₂ in the PANI/SnO ₂ matrix, as observed in the x‐ray diffractogram, confirms the enhancement of order of crystallinity in the composites. Scanning electron microscopy (SEM) was employed to analyze the surface morphology, while UV–vis–NIR spectroscopy and Fourier transform infrared spectrum (FTIR) validated the molecular structures of the developed composites. Furthermore, the temperature‐dependent conductivities of the PANI and PANI/SnO ₂ complexes divulge that the nature of charge transport is semiconducting. The investigation of charge transport in PANI and PANI/SnO ₂ implies that the conduction of charge carriers in PANI mostly abides by the 3‐D Mott Variable range hopping (3D‐VRH) model throughout the experimental temperature range, whilst PANI/SnO ₂ obeys a thermally activated band conduction model (BCM) at high temperature. Density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) computations were carried out on a polaronic and bipolaronic model of emeraldine salt of PANI to obtain their stabilized geometries, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), the HOMO−LUMO energy gap, UV–vis–NIR, and FTIR spectra. Polaronic PANI shows a higher energy for the HOMO−LUMO transition, indicating the deficiency of conjugation compared to a bipolaronic structure. The cohesive experimental and theoretical analysis indicates that pure PANI primarily exhibits a polaronic structure, while doping with SnO ₂ enhances the bipolaronic content in the composites.