Ultrafast Energy Transfer between Disordered and Highly Planarized Chains of Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)

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Unger, Thomas ; Panzer, Fabian ; Consani, Cristina ; Koch, Federico ; Brixner, Tobias ; Bässler, Heinz ; Köhler, Anna:
Ultrafast Energy Transfer between Disordered and Highly Planarized Chains of Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV).
In: ACS Macro Letters. Bd. 4 (2015) Heft 4 . - S. 412-416.
ISSN 2161-1653
DOI: https://doi.org/10.1021/acsmacrolett.5b00133

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Abstract

Upon cooling a solution of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), a phase transition occurs, leading to the formation of aggregates. We have studied the dynamics of singlet excitons in MEH-PPV solution below the critical temperature of the phase transition using steady-state photoluminescence measurements and pump–probe fs-spectroscopy at different temperatures. Spectral analysis indicates the coexistence of disordered chromophores with highly planarized chromophores. The high planarity is evidenced by a remarkably high 0–0/0–1 peak ratio in the spectra. By spectrally separating the contributions of either type of chromophore to the pump–probe signal we find that energy transfer takes place within less than 1 ps from disordered, unaggregated chain segments to highly planarized, aggregated chain segments. The short time scale of the energy transfer indicates intimate intermixing of the planarized and disordered polymeric chromophores.