Hole-induced quenching of triplet and singlet excitons in conjugated polymers
Hole-induced quenching of triplet and singlet excitons in conjugated polymers
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DOI：
10.1021/ja051271i
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发表时间：
2005-07-06
影响因子：
15
通讯作者：
Barbara, PF
中科院分区：
文献类型：
--
作者：
Gesquiere, AJ;Park, SJ;Barbara, PF
采用荧光电压时间分辨单分子光谱（FV-TR-SMS）技术，定量研究了共轭聚合物聚[2-甲氧基-5-（2 '-乙基己氧基）-对苯乙炔]中空穴（自由基阳离子）诱导的三重态和单重态激子猝灭的机理和速率。FV-TR-SMS测量嵌入在电容器样装置中的单个共轭聚合物分子的荧光强度，同时调节装置上的偏压和照射强度。结果表明，在共轭聚合物中，空穴密度> 10（16）电荷/cm（3）时，三重态激子被空穴有效地猝灭，而单重态激子被猝灭的效率低得多。详细的动力学分析表明，空穴对三重态的淬灭效率更高（与单重态相比）是由于三重态的激子寿命长10（6）倍。事实上，这些结果表明，虽然由于单线态寿命短得多，单线态淬灭的效率较低，但空穴对单线态淬灭的速率常数实际上超过了三重态淬灭的速率常数几个数量级。
Quantitative information on the mechanisms and rates of hole (radical cation)-induced quenching of triplet and singlet excitons in the conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] has been acquired by a new technique, fluorescence-voltage time-resolved single molecule spectroscopy (FV-TR-SMS). FV-TR-SMS measures the fluorescence intensity of a single conjugated polymer molecule that is embedded in a capacitor-like device while simultaneously modulating the bias on the device and the irradiation intensity. The results demonstrate that triplet excitons are efficiently quenched by holes in conjugated polymers for hole densities > 10(16) charges/cm(3), while singlet excitons are quenched with a much lower efficiency. Detailed kinetic analysis shows that the greater efficiency for quenching of triplets by holes (compared to that for singlets) is due to a > 10(6) times longer exciton lifetime for triplets. In fact, the results suggest that while singlet quenching is less efficient due to a much shorter singlet lifetime, the rate constant for the quenching of singlets by holes actually exceeds that for triplets by several orders of magnitude.