Favorable Mixing Thermodynamics in Ternary Polymer Blends for Realizing High Efficiency Plastic Solar Cells
Favorable Mixing Thermodynamics in Ternary Polymer Blends for Realizing High Efficiency Plastic Solar Cells
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DOI：
10.1002/aenm.201803394
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发表时间：
2019-04
影响因子：
27.8
通讯作者：
Nicola Gasparini;S. Kahmann;M. Salvador;J. D. Perea;A. Sperlich;A. Baumann;Ning Li;S. Rechberger-S.-Rechbe
中科院分区：
文献类型：
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作者：
Nicola Gasparini;S. Kahmann;M. Salvador;J. D. Perea;A. Sperlich;A. Baumann;Ning Li;S. Rechberger-S.-Rechbe
具有宽光谱吸收的三元共混物有可能增加有机太阳能电池中的电荷产生，但由于有限的混合和电子失配而具有额外的复杂性。这里，提出了包含聚合物聚[5，5-双（2-丁基辛基）-（2，2-联噻吩）-4，4-二羧酸酯-alt-5，5 - 2，2-联噻吩]（PDCBT）和PTB 7-Th以及作为电子接受单元的PC 70 BM的模型系统。三元系统的功率转换效率（PCE）明显超过了二元系统的性能。该物理过程由从PDCBT到PTB 7-Th的快速能量转移过程控制，然后在PTB 7-Th：富勒烯界面进行电子转移。三元共混物中的形态基序的特征在于聚合物纤维。基于物理分析、GIWAXS测量和分子间参数计算的组合，后者表明PDCBT和PTB 7-Th之间具有非常有利的分子亲和力，提出有效的电荷产生机制是可能的，因为PTB 7-Th主要围绕PDCBT细丝定向，允许能量有效地从PDCBT传递到PTB 7-Th。富勒烯可以被非富勒烯受体取代，而不会牺牲电荷产生，从而实现11%以上的PCE。这些结果支持的想法，热力学混合和能量的聚合物-聚合物界面是实现高效的三元太阳能电池与可变电子受体的关键设计参数。
Ternary blends with broad spectral absorption have the potential to increase charge generation in organic solar cells but feature additional complexity due to limited intermixing and electronic mismatch. Here, a model system comprising the polymers poly[5,5‐bis(2‐butyloctyl)‐(2,2‐bithiophene)‐4,4‐dicarboxylate‐alt‐5,5‐2,2‐bithiophene] (PDCBT) and PTB7‐Th and PC70BM as an electron accepting unit is presented. The power conversion efficiency (PCE) of the ternary system clearly surpasses the performance of either of the binary systems. The photophysics is governed by a fast energy transfer process from PDCBT to PTB7‐Th, followed by electron transfer at the PTB7‐Th:fullerene interface. The morphological motif in the ternary blend is characterized by polymer fibers. Based on a combination of photophysical analysis, GIWAXS measurements and calculation of the intermolecular parameter, the latter indicating a very favorable molecular affinity between PDCBT and PTB7‐Th, it is proposed that an efficient charge generation mechanism is possible because PTB7‐Th predominantly orients around PDCBT filaments, allowing energy to be effectively relayed from PDCBT to PTB7‐Th. Fullerene can be replaced by a nonfullerene acceptor without sacrifices in charge generation, achieving a PCE above 11%. These results support the idea that thermodynamic mixing and energetics of the polymer–polymer interface are critical design parameter for realizing highly efficient ternary solar cells with variable electron acceptors.