小分子优先结晶构筑聚合物/非富勒烯共混体系互穿网络结构

非富勒烯小分子受体(SMAs)有序聚集决定聚合物/非富勒烯共混体系光伏电池的双分子复合几率。 然而,由于非对称相分离聚合物趋于优先形成网络,抑制小分子受体分子结晶。 在聚(2,6-(4,8-二(5-(2-乙基己基噻吩-2-基)苯并1,2-b:4,5-b']二噻吩))-alt-(5,5-(1',3'-二-2-噻吩基-5',7'-二(2-乙基己基)苯并1',2'-c:4',5'-c']二噻吩-4,8-二酮))](PBDB-T)/9-二(2-亚甲基(3-(1,1-二氰基亚甲基)-6,7-二氟-茚酮))-5,5,11,11-四(4-己基苯基)-二噻吩并2,3-d:2',3'-d']-s-引达省1,2-b:5,6-b']二噻吩(IT-4F)共混体系,四氢呋喃蒸汽处理可提高IT-4F结晶性,150 ℃热退火可提高PBDB-T的结晶性。 因此,依次利用蒸汽退火和热退火处理薄膜,诱导小分子先结晶、聚合物后结晶,从而降低PBDB-T对小分子扩散的限制,构建高结晶互穿网络结构。 形貌优化后降低了双分子复合,器件光电转换效率从5.95%提高至7.18%。

Constructing Interpenetrating Network of Polymer/Non-fullerene Blend System by Small Molecule Preferential Crystallization

The ordered aggregation of non-fullerene small molecular acceptors(SMAs) is critical in determining the charge transport and bimolecular recombination in polymer/SMAs solar cells. However, due to the asymmetric phase separation, the polymers prefer to form crystalline networks, which inhibits the molecular diffusion of SMAs and results in weak crystallinity of SMAs. In poly(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'bis(2-ethylhexyl)benzo1',2'-c:4',5'-c']dithiophene-4,8-dione))](PBDB-T)/9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6,7-difluoro)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno2,3-d:2',3'-d']-s-indaceno1,2-b:5,6-b']dithiophene(IT-4F) blends, crystallization of IT-4F could be improved by tetrahydrofuran solvent vapor annealing, while crystallization of PBDB-T could be enhanced by thermal annealing at 150 ℃. Hence, the prior crystallization of IT-4F could be realized by regulating the sequence of two post annealing methods, which facilitates the diffusion of IT-4F and is benefit for the formation of interpenetrating network. The optimization of the film morphology reduced the bimolecular recombination and resulted in an improved device performance from 5.95% to 7.18%.