Cadby A, Dean R, Fox A M, Jones R A L, Lidzey D G
Department of Physics and Astronomy, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, U.K.
Nano Lett. 2005 Nov;5(11):2232-7. doi: 10.1021/nl051525y.
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.
我们使用时间分辨扫描近场光学显微镜（SNOM）研究了分散在聚苯乙烯（PS）惰性基质中的聚（9,9-二辛基芴）（F8）聚合物共混物。旋涂时，两种聚合物之间会发生相分离，形成具有富F8相和富PS相的薄膜。通过对薄膜光致发光强度进行空间映射，我们发现富PS相中捕获了低浓度的F8。我们发现，富PS相中捕获的F8的荧光发射寿命（在440nm处测量）明显长于富F8相中的寿命（分别为290ps和235ps）。此外，光谱测量表明，富PS相中的F8发射的特征是芴酮缺陷态发射的比例降低。综合来看，我们的测量结果表明，在富PS相中，稀释效应显著抑制了F8分子之间的链间激子扩散。
