Thermally activated motion of cold excitons in conjugated polymers

Köse, Muhammet E.; Köse, Esra Özay

doi:10.1002/qua.27088

Cited by 2 publications

(1 citation statement)

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“…After formation of hot excitons upon photoexcitation, excitons can relax and form relaxed singlet excitons, and at some special circumstances, conversion of singlet excitons into triplet excitons are possible. The relaxation of hot excitons is usually accompanied by the structural rearrangement of the conjugated backbone. , It is generally observed that double bonds in the ground state adopt more single bond character and single bonds adopt more double bond character during relaxation of either singlet or triplet excitons. One salient outcome of this is the planarization of the conjugated backbone due to more double bond character of single bonds connecting ring structures.…”

Section: Resultsmentioning

confidence: 99%

Activation Energies of Diffusion for Relaxed Singlet and Triplet Excitons over Conjugated Polymer Chains

Erzurumluoglu,

Köse,

Köse

et al. 2024

J. Phys. Chem. C

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Exciton diffusion in nonadiabatic regime can be modeled using an activated expression for relaxed singlet and triplet excitons formed on conjugated chains. A displaced but undistorted harmonic oscillator model has been used to predict the energy required for an exciton to hop to the nearest site on a chain. The activation energies of diffusion for excitons are estimated for some well-known conjugated polymers used in organic electronics. On average, the activation energies for triplet exciton migration have been found to be almost three times larger than those for singlet exciton migration. The activation energies for singlet excitons in a perfectly planar conjugated chain without torsional disorder have been found to be usually lower than the thermal energy available at room temperature. Inclusion of torsional energetic barriers can significantly increase the total activation energy of exciton transport over conjugated chains. The results provide an explanation for longrange exciton transport observed in ordered phases of conjugated polymer films. The theoretical findings also suggest that the activation barriers for exciton diffusion are not very dependent on the electronic structure of the conjugated units but mostly affected by the presence of torsional disorder, which has to be dealt with carefully in computational studies.

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Section: Resultsmentioning

confidence: 99%

Activation Energies of Diffusion for Relaxed Singlet and Triplet Excitons over Conjugated Polymer Chains

Erzurumluoglu,

Köse,

Köse

et al. 2024

J. Phys. Chem. C

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Photoexcited Polaron Relaxation as a Structurally Sensitive Reporter of Charge Trapping in a Conducting Polymer

Umar,

Dorris,

Grieco

2024

Adv Funct Materials

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Conjugated polymers (CPs) play a central role in electronic applications due to their easily tuned electronic and ionic conductivities via chemical or electrochemical doping. Although doping improves charge conduction by introducing high densities of carriers into the CP, the accompanying structural changes and their impact on carrier mobility remain elusive. Methods capable of probing carrier distributions and their dependence on polymer morphology are needed to better understand how to improve conductivity. Here, a transient absorption (TA) spectroscopy approach is demonstrated, capable of directly probing mobile and trapped carriers in doped CPs and that is also sensitive to polymer nanostructure by using a model polythiophene system with tuned crystallinity. Exciting polarons in the polymer films produces distinct photoinduced absorption signals in the near‐infrared spectrum that decay during the picosecond timescale in the form of biphasic, stretched exponential kinetics, which reflect a distribution of mobile (free) and trapped polarons. The kinetic analysis provides evidence for mobile polarons irrespective of polymer film crystallinity, whereas polarons located in impure amorphous phases with reduced chain ordering exist within a deeper distribution of trap states. Altogether, these observations suggest a stronger correlation of carrier trapping with local chain ordering (planarity or aggregation) rather than polymer crystallinity.

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Thermally activated motion of cold excitons in conjugated polymers

Cited by 2 publications

References 37 publications

Activation Energies of Diffusion for Relaxed Singlet and Triplet Excitons over Conjugated Polymer Chains

Activation Energies of Diffusion for Relaxed Singlet and Triplet Excitons over Conjugated Polymer Chains

Photoexcited Polaron Relaxation as a Structurally Sensitive Reporter of Charge Trapping in a Conducting Polymer

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