Song Kyu Chan, Sung Woong, Lee Dong Chan, Chung Sein, Lee Hansol, Lee Jaewon, Cho Shinuk, Cho Kilwon
Department of Chemical Engineering, Pohang University of Science and Technology, Pohang37673, Korea.
Department of Physics and EHSRC, University of Ulsan, Ulsan44610, Korea.
ACS Appl Mater Interfaces. 2022 Nov 23;14(46):52233-52243. doi: 10.1021/acsami.2c13304. Epub 2022 Nov 10.
Nonfused-ring electron acceptors (NFREAs) have received increasing attention for use in organic solar cells (OSCs) because of their synthetic simplicity and tunable optical spectra. However, their fundamental molecular interactions and the mechanism by which they govern the property-function relations of OSCs remain elusive. Here, to investigate the effects of the structural symmetry of NFREAs, two acceptor-donor-acceptor'-donor-acceptor (A-D-A'-D-A)-type NFREAs, 2,2'-(((naphtho[1,2-:5,6-']bis[1,2,5]thiadiazole-5,10-diylbis(4,4-bis(2-butyloctyl)-4-cyclopenta[2,1-:3,4-']dithiophene-6,2-diyl))bis(methaneylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1-indene-2,1-diylidene))dimalononitrile (NTz-4F) and 2,2'-(((benzo[][1,2,5]thiadiazole-4,7-diylbis(4,4-bis(2-ethylhexyl)-4-cyclopenta[2,1-:3,4-']dithiophene-6,2-diyl))bis(methaneylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1-indene-2,1-diylidene))dimalononitrile (BT-4F), are designed and synthesized. They have different A' cores: NTz-4F has a modified centrosymmetric NTz core, whereas BT-4F has a modified axisymmetric BT core. In pristine films, the NTz-4F, which has a centrosymmetric core, shows substantially enhanced intermolecular interaction and microstructural crystalline ordering compared with BT-4F, which has an axisymmetric core. Even in blends with poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-:4,5-']dithiophene))--(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-:4',5'-]dithiophene-4,8,-dione))] (PBDB-T), NTz-4F retains its highly crystalline structure, whereas BT-4F loses crystalline packing. These changes in NTz-4F result in increased electron transport and suppressed nonradiative voltage loss, resulting in a power conversion efficiency of 9.14% for PBDB-T:NTz-4F vs 7.18% for PBDB-T:BT-4F. This work demonstrates that centrosymmetric-structured cores are promising building blocks for high-performance NFREA-based OSCs.
非稠环电子受体（NFREAs）因其合成简便且光谱可调，在有机太阳能电池（OSCs）中的应用受到越来越多的关注。然而，它们基本的分子相互作用以及调控有机太阳能电池性能 - 功能关系的机制仍不明确。在此，为了研究NFREAs结构对称性的影响，设计并合成了两种受体 - 给体 - 受体'-给体 - 受体（A - D - A'-D - A）型NFREAs，即2,2'-(((萘并[1,2 - :5,6 - ']双[1,2,5]噻二唑 - 5,10 - 二基双(4,4 - 双(2 - 丁基辛基)-4 - 环戊并[2,1 - :3,4 - ']二噻吩 - 6,2 - 二基))双(亚甲基))双(5,6 - 二氟 - 3 - 氧代 - 2,3 - 二氢 - 1 - 茚 - 2,1 - 二亚基))二丙二腈（NTz - 4F）和2,2'-(((苯并[][1,2,5]噻二唑 - 4,7 - 二基双(4,4 - 双(2 - 乙基己基)-4 - 环戊并[2,1 - :3,4 - ']二噻吩 - 6,2 - 二基))双(亚甲基))双(5,6 - 二氟 -
3 - 氧代 - 2,3 - 二氢 - 1 - 茚 - 2,1 - 二亚基))二丙二腈（BT - 4F）。它们具有不同的A'核：NTz - 4F具有修饰的中心对称NTz核，而BT - 4F具有修饰的轴对称BT核。在原始薄膜中，具有中心对称核的NTz - 4F与具有轴对称核的BT - 4F相比，显示出显著增强的分子间相互作用和微观结构结晶有序性。即使在与聚[(2,6 - (4,8 - 双(5 - (2 - 乙基己基)噻吩 - 2 - 基)-苯并[1,2 - :4,5 - ']二噻吩)) - (5,5 - (1',3'-二 - 2 - 噻吩基 - 5',7'-双(2 - 乙基己基)苯并[1',2'-:4',5'-]二噻吩 - 4,8,-二酮))]（PBDB - T）共混时，NTz - 4F保留其高度结晶结构，而BT - 4F失去结晶堆积。NTz - 4F的这些变化导致电子传输增加和非辐射电压损失受到抑制，使得PBDB - T:NTz - 4F的功率转换效率为9.14%，而PBDB - T:BT - 4F为7.18%。这项工作表明，中心对称结构的核是基于高性能NFREA的有机太阳能电池的有前景的构建单元。
