Combined experimental and TDDFT computations for the structural and optical properties for poly (ortho phenylene diamine) thin film with different surfactants

Poly(ortho-phenylenediamine) micro-rods (PoPD) are synthesized in the acidic medium at 25 °C by an oxidative polymerization method in the absence or the presence of a soft template including the following surfactants para toluene sulfonic acid (PoPD-PTS) and trisodium citrate (PoPD-TSC). Then, the thin films of poly(ortho-phenylenediamine) (PoPD)^F, toluene sulfonic acid (PoPD-PTS)^F, and trisodium citrate (PoPD-TSC)^F are fabricated using the physical vapor deposition method (PVD). The fabricated thin films are characterized by several techniques includes Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction analysis (XRD), UV–Vis spectroscopy (UV–Vis), scanning electron microscopy (SEM), and optical properties are interpreted in-depth. The optimization for the samples is carried out by applying density functional theory (DFT) with DMol³ and Cambridge Serial Total Energy Package (CASTEP) program. XRD measurements of thin film showed a crystal structure of monoclinic 2, and there is an increase of polymer crystallite size when used PTS and TSC surfactants in the preparation of the polymer. The study of surface morphology shows a smooth surface with uniform micro-rods for the resulting polymer. The optical constants including refractive index (n), absorption index (k) are calculated. Based on the optical measurements, the optical constants decrease with increasing photon energy while optical conductivity, and dielectric constants increase. Following the experimental analysis, the optical properties of simulated FT-IR, XRD, and CATSTEP are in good agreement with the experimental ones. (PoPD-PTS)^F and (PoPD-TSC)^F films are a good applicant for optoelectronics and solar cells.