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Exciton–Exciton Annihilation in Mixed‐Phase Polyfluorene Films
Author(s) -
Shaw Paul E.,
Ruseckas Arvydas,
Peet Jeffrey,
Bazan Guillermo C.,
Samuel Ifor D. W.
Publication year - 2010
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200900879
Subject(s) - exciton , annihilation , materials science , polyfluorene , chromophore , phase (matter) , biexciton , molecular physics , singlet state , photoluminescence , quenching (fluorescence) , diffusion , chemical physics , condensed matter physics , photochemistry , fluorescence , atomic physics , optoelectronics , optics , physics , nanotechnology , chemistry , thermodynamics , layer (electronics) , quantum mechanics , electroluminescence , excited state
Singlet–singlet annihilation is studied in polyfluorene (PFO) films containing different fractions of β ‐phase chains using time‐resolved fluorescence. On a timescale of >15 ps after excitation, the results are fitted well by a time‐independent annihilation rate, which indicates that annihilation is controlled by 3D exciton diffusion. A time‐dependent annihilation rate is observed during the first 15 ps in the glassy phase and in the β ‐phase rich films, which can be explained by the slowdown of exciton diffusion after excitons reach low‐energy sites. The annihilation rate in the mixed‐phase films increases with increasing fraction of β ‐phase present, indicating enhanced exciton diffusion. The observed trend agrees well with a model of fully dispersed β ‐phase chromophores in the surrounding glassy phase with the exciton diffusion described using the line‐dipole approximation for an exciton wavefunction extending over 2.5 nm. The results indicate that glassy and β ‐phase chromophores are intimately mixed rather than clustered or phase‐separated.