Role of Intermolecular Coupling in the Photophysics of Disordered Organic Semiconductors: Aggregate Emission in Regioregular Polythiophene

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Abstract
We address the role of excitonic coupling on the nature of photoexcitations in the conjugated polymer regioregular poly(3-hexylthiophene). By means of temperature-dependent absorption and photoluminescence spectroscopy, we show that optical emission is overwhelmingly dominated by weakly coupled H aggregates. The relative absorbance of the 0–0 and 0–1 vibronic peaks provides a powerfully simple means to extract the magnitude of the intermolecular coupling energy, of approximately 5 and 30 meV for films spun from isodurene and chloroform solutions, respectively.