Correlated-electron description of the photophysics of thin films of $\pi$-conjugated polymers

Abstract

We extend Mulliken's theory of ground state charge transfer in a donor-acceptor complex to excited state charge transfer between pairs of identical $\pi$-conjugated oligomers, one of which is in the optically excited state and the other in the ground state, leading to the formation of a charge-transfer exciton. Within our theory, optical absorptions from the charge-transfer exciton should include a low energy intermolecular charge-transfer excitation, as well as distinct intramolecular excitations from both the neutral delocalized exciton component and the Coulombically bound polaron-pair component of the charge-transfer exciton. We report high order configuration-interaction calculations for pairs of oligomers of poly-paraphenylenevinylene (PPV) that go beyond our previous single configuration-interaction calculation and find all five excited state absorptions predicted using heuristic arguments based on the Mulliken concept. Our calculated excited state absorption spectrum exhibits strong qualitative agreement with the complete wavelength-dependent ultrafast photoinduced absorption in films of PPV derivatives, suggesting that a significant fraction of the photoinduced absorption here is from the charge-transfer exciton. We make detailed comparisons to experiments, and a testable experimental prediction.

References in corpus (4)

• The role of intermolecular coupling in the photophysics of disordered organic semiconductors: Aggregate emission in regioregular polythiophene
• Exciton Regeneration at Polymeric Semiconductor Heterojunctions
• Theory of excited state absorptions in phenylene-based $\pi$-conjugated polymers
• Photophysics of charge-transfer excitons in thin films of π-conjugated polymers

Cited by in corpus (8)

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• Analysis of the excited-state absorption spectral bandshape of oligofluorenes
• Optical Probes of the Quantum-Entangled Triplet-Triplet State in a Heteroacene Dimer
• Charge-transfer excitons in strongly coupled organic semiconductors
• A Fortran 90 Hartree-Fock program for one-dimensional periodic $\pi$-conjugated systems using Pariser-Parr-Pople model
• Manipulation of Charge Delocalization in a Bulk Heterojunction Material Using a Mid-Infrared Push Pulse