Hartnett Patrick E, Matte H S S Ramakrishna, Eastham Nicholas D, Jackson Nicholas E, Wu Yilei, Chen Lin X, Ratner Mark A, Chang Robert P H, Hersam Mark C, Wasielewski Michael R, Marks Tobin J
Department of Chemistry and the Materials Research Center , The Argonne-Northwestern Solar Energy Research Center , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA . Email:
Department of Materials Science and Engineering and the Materials Research Center , The Argonne-Northwestern Solar Energy Research Center , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA.
Chem Sci. 2016 Jun 1;7(6):3543-3555. doi: 10.1039/c5sc04956c. Epub 2016 Feb 9.
A series of perylenediimide (PDI) dimers are evaluated as acceptors for organic photovoltaic (OPV) cells. The materials are characterized using a wide variety of physical and computational techniques. These dimers are first linked at the bay position of each PDI molecule an aromatic spacer; subsequent photocyclization affords ring-fused dimers. Thus, photocyclization of the thiophene-linked dimer 2,5-bis-[,'-bis-perylenediimide-1-yl]-thiophene () affords the twisted acceptor [2,3-:2',3'-]-bis-[,'-bis-perylenediimide-1,12-yl]-thiophene (), while photocyclization of the thienothiophene-linked dimer, 2,5-bis-[,'-bis-perylenediimide-1-yl]-thienothiophene () affords the planar acceptor [2,3-:2',3'-]-bis-[,'-bis-perylenediimide-1,12-yl]-thienothiophene (). Furthermore, a dimer linked by a phenylene group, 1,4-bis-[,'-bis-perylenediimide-1-yl]-benzene (), can be selectively photocyclized to form either the twisted dimer, [1,2:3,4]-bis-[,'-bis-perylenediimide-1,12-yl]-benzene () or the planar dimer [1,2:4,5]-bis-[,'-bis-perylenediimide-1,12-yl]-benzene (). Ring-fusion results in increased electronic coupling between the PDI units, and increased space-charge limited thin film electron mobility. While charge transport is efficient in bulk-heterojunction blends of each dimer with the polymeric donor , in the case of the twisted dimers ring fusion leads to a significant decrease in geminate recombination, hence increased OPV photocurrent density and power conversion efficiency. This effect is not observed in planar dimers where ring fusion leads to increased crystallinity and excimer formation, decreased photocurrent density, and decreased power conversion efficiency. These results argue that ring fusion is an effective approach to increasing OPV bulk-heterojunction charge carrier generation efficiency in PDI dimers as long as they remain relatively amorphous, thereby suppressing excimer formation and coulombically trapped charge transfer states.
一系列苝二亚胺（PDI）二聚体被评估用作有机光伏（OPV）电池的受体。使用多种物理和计算技术对这些材料进行了表征。这些二聚体首先在每个PDI分子的湾区位置与一个芳族间隔基相连；随后的光环化反应得到了稠环二聚体。因此，噻吩连接的二聚体2,5-双-[,'-双苝二亚胺-1-基]-噻吩（）的光环化反应得到了扭曲的受体[2,3-:2',3'-]-双-[,'-双苝二亚胺-1,12-基]-噻吩（），而噻吩并噻吩连接的二聚体2,5-双-[,'-双苝二亚胺-1-基]-噻吩并噻吩（）的光环化反应得到了平面受体[2,3-:2',3'-]-双-[,'-双苝二亚胺-1,12-基]-噻吩并噻吩（）。此外，由亚苯基连接的二聚体1,4-双-[,'-双苝二亚胺-1-基]-苯（）可以被选择性地光环化，形成扭曲的二聚体[1,2:3,4]-双-[,'-双苝二亚胺-1,12-基]-苯（）或平面二聚体[1,2:4,5]-双-[,'-双苝二亚胺-1,12-基]-苯（）。环融合导致PDI单元之间的电子耦合增加，以及空间电荷限制的薄膜电子迁移率增加。虽然在每个二聚体与聚合物供体的本体异质结共混物中电荷传输是有效的，但在扭曲二聚体的情况下，环融合导致双生复合显著减少，因此OPV光电流密度和功率转换效率增加。在平面二聚体中未观察到这种效应，在平面二聚体中，环融合导致结晶度增加和激基缔合物形成，光电流密度降低，功率转换效率降低。这些结果表明，只要PDI二聚体保持相对无定形，环融合就是提高OPV本体异质结电荷载流子产生效率的有效方法，从而抑制激基缔合物形成和库仑俘获电荷转移态。
