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N‐Type Organic Thermoelectrics of Donor–Acceptor Copolymers: Improved Power Factor by Molecular Tailoring of the Density of States
Advanced Materials ( IF 27.4 ) Pub Date : 2018-09-17 , DOI: 10.1002/adma.201804290 Jian Liu 1 , Gang Ye 1, 2 , Bas van der Zee 1 , Jingjin Dong 1 , Xinkai Qiu 1, 2 , Yuru Liu 1, 2 , Giuseppe Portale 1 , Ryan C. Chiechi 1, 2 , L. Jan Anton Koster 1
Advanced Materials ( IF 27.4 ) Pub Date : 2018-09-17 , DOI: 10.1002/adma.201804290 Jian Liu 1 , Gang Ye 1, 2 , Bas van der Zee 1 , Jingjin Dong 1 , Xinkai Qiu 1, 2 , Yuru Liu 1, 2 , Giuseppe Portale 1 , Ryan C. Chiechi 1, 2 , L. Jan Anton Koster 1
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It is demonstrated that the n‐type thermoelectric performance of donor–acceptor (D–A) copolymers can be enhanced by a factor of >1000 by tailoring the density of states (DOS). The DOS distribution is tailored by embedding sp2‐nitrogen atoms into the donor moiety of the D–A backbone. Consequently, an electrical conductivity of 1.8 S cm−1 and a power factor of 4.5 µW m−1 K−2 are achieved. Interestingly, an unusual sign switching (from negative to positive) of the Seebeck coefficient of the unmodified D–A copolymer at moderately high dopant loading is observed. A direct measurement of the DOS shows that the DOS distributions become less broad upon modifying the backbone in both pristine and doped states. Additionally, doping‐induced charge transfer complexes (CTC) states, which are energetically located below the neutral band, are observed in DOS of the doped unmodified D–A copolymer. It is proposed that charge transport through these CTC states is responsible for the positive Seebeck coefficients in this n‐doped system. This is supported by numerical simulation and temperature dependence of Seebeck coefficient. The work provides a unique insight into the fundamental understanding of molecular doping and sheds light on designing efficient n‐type OTE materials from a perspective of tailoring the DOS.
中文翻译：
施主-受主共聚物的N型有机热电学：通过分子密度调节态密度提高功率因数
结果表明，通过调整态密度（DOS），可将供体-受体（DA）共聚物的n型热电性能提高1000倍以上。通过将sp 2-氮原子嵌入D–A主链的供体部分来定制DOS分布。因此，电导率为1.8 S cm -1和功率因数为4.5 µW m -1 K -2实现。有趣的是，在中等高的掺杂剂负载下，未改性的D–A共聚物的塞贝克系数出现了不寻常的符号转换（从负到正）。对DOS的直接测量表明，在原始状态和掺杂状态下修改主链时，DOS分布都变得不那么宽。另外，在掺杂的未改性D–A共聚物的DOS中观察到掺杂诱导的电荷转移络合物（CTC）的状态在能量上位于中性带之下。建议通过这些CTC状态的电荷传输负责该n掺杂系统中的正塞贝克系数。塞贝克系数的数值模拟和温度相关性对此提供了支持。
更新日期：2018-09-17
中文翻译：
施主-受主共聚物的N型有机热电学：通过分子密度调节态密度提高功率因数
结果表明，通过调整态密度（DOS），可将供体-受体（DA）共聚物的n型热电性能提高1000倍以上。通过将sp 2-氮原子嵌入D–A主链的供体部分来定制DOS分布。因此，电导率为1.8 S cm -1和功率因数为4.5 µW m -1 K -2实现。有趣的是，在中等高的掺杂剂负载下，未改性的D–A共聚物的塞贝克系数出现了不寻常的符号转换（从负到正）。对DOS的直接测量表明，在原始状态和掺杂状态下修改主链时，DOS分布都变得不那么宽。另外，在掺杂的未改性D–A共聚物的DOS中观察到掺杂诱导的电荷转移络合物（CTC）的状态在能量上位于中性带之下。建议通过这些CTC状态的电荷传输负责该n掺杂系统中的正塞贝克系数。塞贝克系数的数值模拟和温度相关性对此提供了支持。
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