The polyaniline was doped with sulfonic acid and functionalized with single-walled carbon nanotubes. The effects of single-walled carbon nanotubes (SWCNTs) inserting and thermal annealing at T = 393 K, during 24 h are carried out by optical and structural study. Structural characterizations of D-polyaniline (PANI) or D-PANI/SWCNTs compounds at both pristine and annealed states were obtained by Fourier Transform infrared analysis and scanning and transmission electron microscopies. Optical parameters including absorption coefficient, optical transition type, energy gaps, skin depth, and extinction coefficient have been also elucidated from optical absorption measurements. Moreover, the characteristics of the localized states introduced either by SWCNTs adding and/or annealing temperature are carried out. By referring to the starting material, the direct (indirect) optical band gap was found to be reduced from 3.91 (3.75) to 2.35 (2.24) eV, after SWCNTs inserting and annealing. Moreover, new localized states having a band width of 390 meV are created at 1.25 eV. The SWCNTS dispersion quality on the organic matrix and the PANI self-crosslinking lead to the charge transfer and the resulting interpenetrating network can be used as active layers for organic solar cells. POLYM. COMPOS., 40: E821-E831, 2019.

Polyaniline (PANI) was chemically doped and functionalized with single walled carbon nanotubes (SWCNTs). Various characterization methods were employed to study the structure and optical properties of PANI/SWCNTs nanocomposite, such as Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), optical absorption, and stationary photoluminescence. Additionally, a theoretical study using density functional theory calculations was also carried out. It has been demonstrated that the doping process may reduce the band gap without affecting the molecular structure, leading to a better compatibility with the solar spectrum. Moreover, the functionalization process with SWCNTs was able to significantly improve the properties of the resulting nanocomposite. The final interpenetrating network of PANI/SWCNTs exhibited an optical gap of nearly 2.28 eV, from which localized states induced by the charge transfer were created at nearly 1.70 eV. In addition, the resulting donor–acceptor network leads to a separation of electron holes pairs rather than their recombination, which can be used as an active layer in photovoltaic applications and a photocatalyst for advanced oxidation processes.