Cadby A, Dean R, Fox AM, Jones RAL, Lidzey DG. Mapping the fluorescence decay lifetime of a conjugated polymer in a phase-separated blend using a scanning near-field optical microscope.
NANO LETTERS 2005;
5:2232-7. [PMID:
16277459 DOI:
10.1021/nl051525y]
[Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We have studied a blend of the polymers poly(9,9-dioctylfluorene) (F8) dispersed in an inert matrix of polystyrene (PS) using time-resolved scanning near-field optical microscopy (SNOM). On spin-casting, phase separation occurs between the two polymers resulting in a thin film characterized by an F8-rich phase and a PS-rich phase. By spatially mapping the intensity of photoluminescence from the film, we find that there is a low concentration of F8 trapped within the PS-rich phase. We find that the fluorescence emission lifetime (measured at 440 nm) of F8 trapped within the PS-rich phase is significantly longer than that from the F8-rich phase (290 ps compared to 235 ps). Furthermore, spectral measurements indicate that the F8 emission from the PS-rich phase is characterized by a reduced fraction of emission from fluorenone defect states. Taken together, our measurements suggest that in the PS-rich phase interchain exciton diffusion between F8 molecules is suppressed significantly by the effect of dilution.
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