Carrier Screening Controls Transport in Conjugated Polymers at High Doping Concentrations
Carrier Screening Controls Transport in Conjugated Polymers at High Doping Concentrations
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载流子筛选控制高掺杂浓度共轭聚合物中的输运
DOI：
10.1103/physrevlett.131.248101
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发表时间：
2023
影响因子：
8.6
通讯作者：
Akšamija, Zlatan
中科院分区：
文献类型：
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作者：
Duhandžić, Muhamed;Lu-Dìaz, Michael;Samanta, Subhayan;Venkataraman, Dhandapani;Akšamija, Zlatan
掺杂共轭聚合物的输运性质已经被广泛地用高斯无序模型（GDM）结合局域态之间的跳跃输运来分析。这些模型表明，即使在高度掺杂的CP中，大多数载流子仍然是局部的，因为CP的介电常数远低于无机材料的介电常数，使得载流子和掺杂剂反离子之间的库仑相互作用更加明显。然而，以前的研究中的GDM没有考虑的载体筛选介电相互作用的作用。在这里，我们实现了载流子屏蔽在德拜-休克尔形式主义在我们的计算掺杂剂引起的高能无序，修改高斯态密度（DOS）。然后，我们解决泡利主方程使用米勒-亚伯拉罕跳跃率与状态从所产生的屏蔽DOS，以获得电导率和塞贝克系数在很宽的范围内的载流子浓度，并比较它们的测量。我们的研究结果表明，筛选有显着的影响的DOS的形状，从而对载流子输运，特别是在高掺杂。我们证明，塞贝克系数与电导率的斜率，这是以前被认为是普遍的，是受筛选和减少系统与小的掺杂剂载体分离，解释我们的测量。我们还表明，热电功率因数被低估的一个因素，在较高的掺杂浓度，如果屏蔽被忽略。我们的结论是载体筛选起着至关重要的作用，在减少掺杂剂引起的充满活力的障碍，特别是在高载流子浓度。
Transport properties of doped conjugated polymers (CPs) have been widely analyzed with the Gaussian disorder model (GDM) in conjunction with hopping transport between localized states. These models reveal that even in highly doped CPs, a majority of carriers are still localized because dielectric permittivity of CPs is well below that of inorganic materials, making Coulomb interactions between carriers and dopant counterions much more pronounced. However, previous studies within the GDM did not consider the role of screening the dielectric interactions by carriers. Here we implement carrier screening in the Debye-Hückel formalism in our calculations of dopant-induced energetic disorder, which modifies the Gaussian density of states (DOS). Then we solve the Pauli master equation using Miller-Abrahams hopping rates with states from the resulting screened DOS to obtain conductivity and Seebeck coefficient across a broad range of carrier concentrations and compare them to measurements. Our results show that screening has significant impact on the shape of the DOS and consequently on carrier transport, particularly at high doping. We prove that the slope of Seebeck coefficient versus electric conductivity, which was previously thought to be universal, is impacted by screening and decreases for systems with small dopant-carrier separation, explaining our measurements. We also show that thermoelectric power factor is underestimated by a factor ofat higher doping concentrations if screening is neglected. We conclude that carrier screening plays a crucial role in curtailing dopant-induced energetic disorder, particularly at high carrier concentrations.