Exciton-Exciton Annihilation in Mixed-Phase Polyfluorene Films
Exciton-Exciton Annihilation in Mixed-Phase Polyfluorene Films
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DOI：
10.1002/adfm.200900879
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发表时间：
2010-01-08
影响因子：
19
通讯作者：
Samuel, Ifor D. W.
中科院分区：
文献类型：
--
作者：
Shaw, Paul E.;Ruseckas, Arvydas;Samuel, Ifor D. W.
用时间分辨荧光研究了不同β相链含量的聚芴（PFO）薄膜中的单重态-单重态湮灭。在激发后>15 ps的时间尺度上，结果与时间无关的湮灭速率很好地拟合，这表明湮灭受三维激子扩散控制。在玻璃相和β相富膜中的前15 ps期间观察到随时间变化的湮灭率，这可以通过激子到达低能位点后激子扩散的减缓来解释。混合相薄膜中的湮灭率随着β相存在的分数的增加而增加，表明增强的激子扩散。所观察到的趋势与模型完全分散的β-相发色团在周围的玻璃相与激子扩散使用线偶极子近似的激子波函数延伸超过2.5 nm。结果表明，玻璃态和β相发色团是紧密混合的，而不是聚集或相分离。
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.