Charge-carrier relaxation dynamics in highly ordered poly(p-phenylene vinylene): Effects of carrier bimolecular recombination and trapping
Charge-carrier relaxation dynamics in highly ordered poly(p-phenylene vinylene): Effects of carrier bimolecular recombination and trapping
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DOI：
10.1103/physrevb.72.245204
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发表时间：
2005-12
影响因子：
3.7
通讯作者：
C. Soci;D. Moses;Qing-Hua Xu;A. Heeger
中科院分区：
文献类型：
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作者：
C. Soci;D. Moses;Qing-Hua Xu;A. Heeger
我们使用快速 t 100 ps 瞬态光电导测量研究了在很宽的时间范围内高度有序的聚对亚苯基亚乙烯基中的载流子弛豫动力学。还通过在红外主动振动模式下探测的光致吸收来监测载流子密度t 100 fs。我们发现，在载流子光生过程中，初始极化子动力学由双分子复合控制，而随后在亚纳秒时间范围内载流子捕获导致光电流呈指数衰减。更灵敏的瞬态光电流测量表明，在低激发状态下，当光载流子的密度与捕获态 10 16 cm �3 相当时，载流子在陷阱之间的跳跃以及通过扩展态的传输决定了载流子弛豫，这种机制通过长寿命的光电流“尾部”来体现。通过降低温度和/或增加激发密度可以减少光电流尾部。基于这些数据，我们开发了一个综合动力学模型，该模型考虑了双极电荷传输、自由载流子双分子复合、载流子俘获以及涉及自由载流子和俘获载流子的载流子复合。
We have studied the charge-carrier relaxation dynamics in highly ordered polyp-phenylene vinylene over a broad time range using fast t 100 ps transient photoconductivity measurements. The carrier density was also monitored t 100 fs by means of photoinduced absorption probed at the infrared active vibrational modes. We find that promptly upon charge-carrier photogeneration, the initial polaron dynamics is governed by bimolecular recombination, while later in the subnanosecond time regime carrier trapping gives rise to an exponential decay of the photocurrent. The more sensitive transient photocurrent measurements indicate that in the low excitation regime, when the density of photocarriers is comparable to that of the trapping states 10 16 cm �3 , carrier hopping between traps along with transport via extended states determines the carrier relaxation, a mechanism that is manifested by a long-lived photocurrent “tail.” This photocurrent tail is reduced by lowering the temperature and/or by increasing the excitation density. Based on these data, we develop a comprehensive kinetic model that takes into account the bipolar charge transport, the free-carrier bimolecular recombination, the carrier trapping, and the carrier recombination involving free and trapped carriers.