Optical Absorption of Poly(thiophene vinylene) Conjugated Polymers. Experiment and First Principle Theory

TL;DR

This study combines experimental optical absorption measurements and first principles DFT calculations to analyze the electronic structure and interchain interactions in poly(thiophene vinylene) conjugated polymers, revealing new insights into their optical properties.

Contribution

It provides the first combined experimental and theoretical analysis of PTV polymers' optical absorption and atomic geometries, highlighting interchain interactions and phase-dependent absorption features.

Findings

Observed a dominant absorption peak at 577 nm and shoulders at 619 nm and 685 nm.

Theoretical DFT predicts two equilibrium geometries with different interchain distances.

Long-wavelength shoulder correlates with increased interchain interaction and phase changes.

Abstract

Optical absorption spectra of poly(thiophene vinylene) (PTV) conjugated polymers have been studied at room temperature in the spectral range of 450 to 800 nm. A dominant peak located at 577 nm and a prominent shoulder at 619 nm are observed. Another shoulder located at 685 nm is observed at high concentration and after additional treatment (heat, sonification) only. Equilibrium atomic geometries and optical absorption of PTV conjugated polymers have also been studied by first principles density functional theory (DFT). For PTV in solvent, the theoretical calculations predict two equilibrium geometries with different interchain distances. By comparative analysis of the experimental and theoretical data, it is demonstrated that the new measured long-wavelength optical absorption shoulder is consistent with new optical absorption peak predicted for most energetically favorable PTV phase in the solvent. This shoulder is interpreted as a direct indication of increased interchain interaction in the solvent which has caused additional electronic energy structure transformations.