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Interplay between intrachain and interchain interactions in semiconducting polymer assemblies: the HJ-aggregate model
1Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA.
The Journal of Chemical Physics
|May 16, 2012
Summary
A new model analyzes polymer aggregate photophysics, considering exciton motion within and between chains. It reveals how intrachain and interchain couplings dictate H-aggregate or J-aggregate behavior in materials like PDA and P3HT.
Area of Science:
- Materials Science
- Physical Chemistry
- Polymer Science
Background:
- Polymer aggregates exhibit unique photophysical properties influenced by exciton dynamics.
- Understanding the interplay of intrachain and interchain interactions is crucial for controlling these properties.
Purpose of the Study:
- To introduce a novel model (HJ-aggregate model) for analyzing polymer aggregate photophysics.
- To investigate the competition between intrachain (Wannier-Mott) and interchain (Frenkel) excitons.
- To elucidate the factors governing H-aggregate and J-aggregate behavior in polydiacetylene (PDA) and poly(3-hexylthiophene) (P3HT) systems.
Main Methods:
- Development of a Holstein-based Hamiltonian in a multi-particle basis set.
- Detailed analysis of two model dimers: PDA and regioregular P3HT.
- Examination of the temperature dependence of photoluminescence (PL) and radiative decay rates.
Main Results:
- Photophysical properties critically depend on the relative magnitudes of intrachain and interchain exciton bandwidths.
- PDA dimers exhibit J-aggregate characteristics with a temperature-dependent PL ratio, showing an H to J transition.
- P3HT photoluminescence behavior (H or J) is tunable by morphology, with ordered nanofibers favoring J-aggregate behavior.
Conclusions:
- The HJ-aggregate model accurately predicts H-aggregate and J-aggregate behaviors based on exciton bandwidths.
- A thermally activated superradiance regime is predicted for systems with dominant intrachain coupling.
- Morphology control offers a pathway to tune the photophysical response of P3HT aggregates.
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