Regensburg 2016 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 39: Focus: Triplet States in Organic Optoelectronics II

CPP 39.4: Vortrag

Mittwoch, 9. März 2016, 16:00–16:15, H37

The Nature of Fluorescence Quenching in Single Conjugated Polymer Chains vs. Mesoscopic Aggregates — •Florian Steiner, Jan Vogelsang, and John M. Lupton — Department of Experimental and Applied Physics, University Regensburg, Germany

The photophysics of isolated chains and a bulk film of conjugated polymers (CP) such as poly(3-hexylthiophene) (P3HT) differ substantially. Most prominently, the fluorescence quantum yield drops by at least one order of magnitude upon the transition from dissolved chains to bulk film. The mechanisms behind these differences however are still not fully understood. Here we show that we can clarify the question of fluorescence quenching in CP by using single-particle spectroscopy techniques which can be applied to single polymer chains as well as to isolated aggregates consisting of many polymer chains. By investigating the photon statistics from one single chain at a time, we show that the fluorescence quenching mechanism in P3HT can be attributed to the efficient formation of long-lived triplet states, which are able to quench the fluorescence of the total chain by singlet-triplet annihilation [1]. By applying solvent vapor annealing we are able to grow aggregates of CP. Subsequent single-aggregate photon correlation spectroscopy identifies additional "dark" states, which are more rapidly formed compared to the triplet state. We attribute these "dark" states evolving in the mesoscopic size regime of P3HT to charge transfer states, which play the main role in the strong quenching of the fluorescence at the transition from the single molecule to the bulk film.

[1] F. Steiner et al., PRL 112, 137402 (2014)