Influence of molecular designs on polaronic and vibrational transitions in a conjugated push-pull copolymer

Abstract

Electron-phonon interactions of free charge-carriers in doped pi-conjugated polymers are conceptually described by 1-dimensional (1D) delocalization. Thereby, polaronic transitions fit the 1D-Froehlich model in quasi-confined chains. However, recent developments in conjugated polymers have diversified the backbones to become elaborate heterocylcic macromolecules. Their complexity makes it difficult to investigate the electron-phonon coupling. In this work we resolve the electron-phonon interactions in the ground and doped state in a complex push-pull polymer. We focus on the polaronic transitions using in-situ spectroscopy to work out the differences between single-unit and push-pull systems to obtain the desired structural- electronic correlations in the doped state. We apply the classic 1D-Froehlich model to generate optical model fits. Interestingly, we find the 1D-approach in push-pull polarons in agreement to the model, pointing at the strong 1D-character and plain electronic structure of the push-pull structure. In contrast, polarons in the single-unit polymer emerge to a multi- dimensional problem difficult to resolve due to their anisotropy. Thus, we report an enhancement of the 1D-character by the push-pull concept in the doped state - an important view in light of the main purpose of push-pull polymers for photovoltaic devices.

Biofunctionalized conductive polymers enable efficient CO 2 electroreduction

“…3A ). These are signature infrared-activated vibrations originating from the strong electron-phonon coupling due to doping-induced distortions ( 47 , 48 ). We also synthesized nonconductive PDA, the spectrum of which lacked these kinds of features.…”

Anderson‐Localization and the Mott–Ioffe–Regel Limit in Glassy‐Metallic PEDOT

“…There exists a tremendous interest in metallic polymers as they combine facile processing, high conductivity and transparency. However, to date no straightforward method has been found to engineer a system that unites high doping and high order . The apparent conflict lies in the nature of doping of a conducting polymer, which occurs through a distinct mechanism compared to inorganic semiconductors.…”

“…However, to date no straightforward method has been found to engineer a system that unites high doping and high order. [1][2][3][4][5][6] The apparent conflict lies in the nature of doping of a conducting polymer, which occurs through a distinct mechanism compared to inorganic semiconductors. Severe lattice distortions arise in the doping of conducting polymers as a result of the penetration of ions into the system.…”

Molecular Doping of a Water‐Soluble Polythiophene Derivative

“…The broad band around 0.77 eV of the polaron transition P1 is less pronounced than in the ATR‐FTIR spectra (Figure b). The polaron transition P2, which would be expected at around 1.4 eV, overlaps with the dopant features, as in the UV/VIS‐NIR spectrum (Figure a). Overall, the spectroscopic results strongly support the IPA mechanism and the formation of polaronic sub‐gap states that we derived from the energy level alignment, as shown in Figure b.…”