Molecular Control of Charge Carrier and Seebeck Coefficient in Hybrid Two-Dimensional Nanoparticle Superlattices
Molecular Control of Charge Carrier and Seebeck Coefficient in Hybrid Two-Dimensional Nanoparticle Superlattices
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DOI：
10.1021/acs.jpcc.9b08185
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发表时间：
2020-01-09
影响因子：
3.7
通讯作者：
Hihath, Joshua
中科院分区：
文献类型：
--
作者：
McCold, Cliff E.;Domulevicz, Lucas;Hihath, Joshua
高效热电材料的发展将使能量收集能力发生革命性的变化，并将在大量应用中发挥作用。有机-无机混合纳米结构材料是开发高效热电系统的一个有趣的平台，因为它可以通过智能选择材料成分来独立控制材料的热导率和电导率。在这项研究中，我们通过系统地改变分子的性质来控制二维纳米粒子-分子杂化超晶格的热电势。五个共轭的梯形杂二烯分子被用来连接金纳米颗粒和控制薄膜的性质。有趣的是，我们测量了Seebeck系数符号的变化，对应于大多数电荷载流子(从空穴到电子)的交叉。霍尔效应测量被用来证实这些系统的主要载流子的变化。将密度泛函理论(DFT)与基于格林函数的输运计算相结合，考察了系统中的能级排列。由这些结果预测的单分子Seebeck系数与分子阵列的实验结果相吻合，并为揭示体系中载流子符号变化的根源提供了潜在的见解。此外，对于混合系统，热电功率因数σS-2被发现在高于预测值的范围内，并且偏离了传统材料的优化策略。重点介绍了进一步增加西格玛S-2的简单策略。讨论了模型的局限性和实验结果的变异性来源。我们的发现加深了对分子-纳米颗粒杂化薄膜中电荷传输的理解；证明了这些杂化材料可以方便地控制材料的载流子类型和功率因数，这两者对于最大化功能热电设备的效率都很重要；并为继续最大限度地提高这些材料的热电效率建立了框架。
The development of high efficiency thermoelectric materials would revolutionize energy harvesting capabilities and be useful for a large number of applications. Hybrid organic-inorganic nanostructured materials are an intriguing platform for developing efficient thermoelectric systems due to the possibility of independently controlling the thermal and electrical conductivity of the material with intelligent choices for material components. In this study we control the thermopower of hybrid 2-dimensional (2D) nanoparticle-molecule superlattices by systematically modifying molecular properties. Five conjugated, ladder-type, heteroacene molecules are used to interlink gold nanoparticles and control the thin films' properties. Interestingly, we measure a change in the sign of the Seebeck coefficient, corresponding to a crossover of the majority charge carrier (from hole to electron). Hall-effect measurements are used to confirm the change in dominant carrier for these systems. And density functional theory (DFT) is used in combination with Green's function-based transport calculations to examine the energy level-alignments in the system. The single-molecule Seebeck coefficient predictions from these results compare favorably with the experimental results of the molecular arrays and provide potential insights into the origins of the sign-change of the carriers in the system. In addition, the thermoelectric power factor sigma S-2 is found to range above predicted values for hybrid systems and to deviate from optimization strategies for conventional materials. A simple strategy to further increase sigma S-2 is highlighted. Limitations of the model and sources of variability in the experimental results are discussed. Our findings develop a stronger understanding of charge transport in molecule-nanoparticle hybrid films; demonstrate that these hybrid materials allow facile control over both the carrier type and the power factor of the material, both of which are important for maximizing the efficiency of functional thermoelectric devices; and establish a framework for continuing to maximize the thermoelectric efficiency of these materials.