Light-Induced ESR Studies of Quadrimolecular Recombination Kinetics of Photogenerated Charge Carriers in Regioregular Poly(3-alkylthiophene)/C60 Composites: Alkyl Chain Dependence
Light-Induced ESR Studies of Quadrimolecular Recombination Kinetics of Photogenerated Charge Carriers in Regioregular Poly(3-alkylthiophene)/C60 Composites: Alkyl Chain Dependence
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DOI：
10.1143/jjap.46.5187
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发表时间：
2007-08
影响因子：
1.5
通讯作者：
Hisaaki Tanaka;Naoki Hasegawa;Tomotaka Sakamoto;K. Marumoto;S. Kuroda
中科院分区：
文献类型：
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作者：
Hisaaki Tanaka;Naoki Hasegawa;Tomotaka Sakamoto;K. Marumoto;S. Kuroda
用具有不同烷基链的聚合物(CmH_2m+1，m=6，8，10，12)，对区域规整聚(3-烷基噻吩基)(RR-P3AT)与C60的复合材料进行了光诱导ESR(LESR)测量。以前报道过的光生载流子的四分子复合(QR)动力学已经从激发功率(IEX)与LESR强度的关系中得到证实，表现出∼Iex0.25的依赖关系。LESR强度的时间衰减也符合QR模型。考虑到在区域随机聚合物复合材料中只观察到双分子复合，QR的出现强烈地表明区域规则聚合物链上形成了双电荷态，即双极化子对或极化子对。另一方面，QR速率常数γ表现出弱的烷链依赖性，与具有系统烷链依赖性的纯区域规则聚合物的场效应迁移率相反。这意味着聚合物和富勒烯界面在测定γ方面做出了重大贡献。
Light-induced ESR (LESR) measurements have been performed on the composites of regioregular poly(3-alkylthiophene) (RR-P3AT) and C60 by using polymers having different alkyl chains (CmH2m+1 with m=6, 8, 10, 12). The quadrimolecular recombination (QR) kinetics of photogenerated charge carriers, previously reported, have been confirmed for all the composites from the excitation power (Iex) dependence of the LESR intensity showing an ∼Iex0.25 dependence. The time decay of LESR intensity is also consistent with the QR model. Considering that only bimolecular recombination is observed in regiorandom polymer composites, the occurrence of QR strongly suggests the formation of doubly charged states, either bipolarons or polaron pairs on the regioregular polymer chains. On the other hand, the QR rate constant γ has been found to exhibit weak alkyl chain dependence, contrary to the case of the field-effect mobility of pure regioregular polymers with systematic alkyl chain dependence. This implies the significant contribution of the polymer and fullerene interface in determining γ.