Coexisting Glassy Phases with Different Compositions in NFA-Based Bulk Heterojunctions
Coexisting Glassy Phases with Different Compositions in NFA-Based Bulk Heterojunctions
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DOI：
10.1021/acsmaterialslett.2c00625
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发表时间：
2022-09
影响因子：
11.4
通讯作者：
Oded Nahor;Aditi Khirbat;S. Schneider;M. Toney;N. Stingelin;G. Frey
中科院分区：
文献类型：
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作者：
Oded Nahor;Aditi Khirbat;S. Schneider;M. Toney;N. Stingelin;G. Frey
有机太阳能电池（OSC）本体异质结（BHJ）通常具有丰富的相形态，其相组成和分布显着影响电荷产生、复合和提取等过程，进而影响器件性能。虽然基于富勒烯的 BHJ 在结构上相对较好地理解，特别是当使用与柔性链供体的共混物时，但供体：非富勒烯受体 (NFA) 共混物更难以阐明。原因是 NFA 经常表现出不同的多晶型物；此外，它们的玻璃态可能很复杂。重点关注广泛研究的供体聚合物聚(3-己基噻吩-2,5-二基) (P3HT) 和原型 NFA 的共混物， 3,9-双(2-亚甲基-(3-(1,1-二氰亚甲基)-茚满酮))-5,5,11,11-四(4-己基苯基)-二噻吩并[2,3-d:2′,3′-d′]-s-茚并烯基[1,2-b:5,6-b′]二噻吩(ITIC),我们在这里揭示了两种玻璃态的共存相：分子混合且富含 ITIC 的相。在富含 P3HT 的共混物中，两种玻璃相均以纳米级域的形式存在，均匀分布在 BHJ 中，如通过气相渗透 (VPI)“染色”所观察到的。相比之下，1:1（按重量计）和富含 NFA 的共混物在玻璃相的大域（>500 nm）和不受退火影响的较薄的富含聚合物域之间显示出清晰的横向相分离。我们的观察有助于解释早期的 P3HT：ITIC 设备研究；还强调了基于 NFA 的 BHJ 的复杂性，强调需要更深入地了解此类系统的相行为。
Organic solar cell (OSC) bulk heterojunctions (BHJ) typically feature a rich phase morphology with the phase composition and distribution significantly affecting processes such as charge generation, recombination and extraction, and in turn, device performance. While fullerene-based BHJs are relatively well understood structurally, especially when blends with a flexible-chain donor are employed, donor: non-fullerene acceptor (NFA) blends are more challenging to elucidate. The reason is that NFAs often display different polymorphs; moreover, their glassy states can be complex. Focusing on blends of the widely investigated donor polymer, poly(3-hexylthiophene-2,5-diyl) (P3HT), and the prototype NFA, 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC), we reveal here the coexistence of two glassy phases: a molecularly intermixed and an ITIC-rich one. In P3HT-rich blends, both glassy phases are present as nanosized domains, evenly distributed in the BHJ, as visualized via vapor phase infiltration (VPI) “staining”. In contrast, the 1:1 (by weight) and NFA-rich blends show clear, lateral phase separation between large (>500 nm) domains of the glassy phases and thinner polymer-rich domains that are unaffected by annealing. Our observations help to explain earlier P3HT: ITIC device studies; and also highlight the complexity of NFA-based BHJs, emphasizing the need for a deeper understanding of the phase behavior of such systems.