Exciton-Exciton Annihilation in Mixed-Phase Polyfluorene Films

Paul E. Shaw, Arvydas Ruseckas, Jeffrey Peet, Guillermo C. Bazan, Ifor D. W. Samuel

Research output: Contribution to journalArticlepeer-review

58 Citations (Scopus)

Abstract

Singlet-singlet annihilation is studied in polyfluorene (PFO) films containing different fractions of beta-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 beta-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 beta-phase present, indicating enhanced exciton diffusion. The observed trend agrees well with a model of fully dispersed beta-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 beta-phase chromophores are intimately mixed rather than clustered or phase-separated.

Original languageEnglish
Pages (from-to)155-161
Number of pages7
JournalAdvanced Functional Materials
Volume20
Issue number1
DOIs
Publication statusPublished - 8 Jan 2010

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