Carrier generation process on photoconductive polymer films as studied by magnetic field effects on the charge-transfer fluorescence and photocurrent
Carrier generation process on photoconductive polymer films as studied by magnetic field effects on the charge-transfer fluorescence and photocurrent
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DOI：
10.1021/jp0453212
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发表时间：
2005-05-12
影响因子：
3.3
通讯作者：
Tero-Kubota, S
中科院分区：
文献类型：
--
作者：
Ito, F;Ikoma, T;Tero-Kubota, S
研究了磁场对1，2，4，5-四氰基苯掺杂聚（N-乙烯基咔唑）薄膜的电荷转移荧光和瞬态光电流的影响，它们分别反映了载流子的复合和逃逸产率.复合产量的外部磁场（B）的依赖性清楚地显示了两种类型的MFE，增长与增加B由于超精细机制（HFM）和负倾角由于水平交叉机制（LCM）。另一方面，逃逸产率表明互补MFE的产率随着B的增加而急剧下降，然后出现正下降。同时观察的HFM和LCM-MFE证明了逐步空穴跳跃机制，而不是远程空穴跳跃之一。利用随机Liouville方程（SLE）对自旋守恒条件下最近邻咔唑单元间空穴跳跃的一维晶格模型进行了复合和逃逸MFE的定量分析. SLE分析提供的复合和空穴传输速率常数分别为7.0 × 10（7）和4.5 × 10（8）s（-1）。在一维模型中的离子对的边界网站数估计的最佳拟合的实验结果。一维八位模型中边界离子对的电子距离与Onsager模型中的热化距离一致。因此，可以得出结论，在Onsager模型中的基本过程适用于分子无定形固体是逐步的空穴跳跃，而不是一个远程空穴跳跃。
We have studied the magnetic field effects (MFEs) on the charge-transfer fluorescence and transient photocurrent of a 1,2,4,5-tetracyanobenzene-doped poly(N-vinylcarbazole) film, which reflect the recombination and escape yields of the carriers, respectively. The recombination yield dependence of the external magnetic field (B) clearly shows two types of the MFEs, growth with increasing B due to the hyperfine mechanism (HFM) and a negative dip due to the level-crossing mechanism (LCM). On the other hand, the escape yield indicates complementary MFEs with a sharp decrease in yield with increasing B and then a positive dip. Simultaneous observation of the HFM- and LCM-MFEs proves the stepwise hole-hopping mechanism rather the long-range hole-jumping one. The quantitative analysis of the recombination and escape MFEs is performed using the stochastic Liouville equations (SLE) for a one-dimensional lattice model in which the stepwise hole hops take place between the nearest neighbor carbazole units with spin conservation. The SLE analysis provides the recombination and hole transfer rate constants of 7.0 x 10(7) and 4.5 x 10(8) s(-1), respectively. The boundary site number for the ion pairs in the one-dimensional model is estimated by the best fit to the experimental results. The interionic distance of the boundary ion pair in the one-dimensional model including eight sites agrees with the thermalization distance in the Onsager model. Hence, it is concluded that the elementary processes in the Onsager model applied to molecular amorphous solids are the stepwise hole hops rather than a long-range hole jump.