State Key Laboratory of Silicon Materials, MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, P. R. China.
Faculte des Sciences, Laboratoire Chimie des Polymeres, Universite Libre de Bruxelles , CP 206/1, Boulevard du Triomphe, 1050 Bruxelles, Belgium.
ACS Appl Mater Interfaces. 2016 Aug 17;8(32):20916-27. doi: 10.1021/acsami.6b05084. Epub 2016 Aug 2.
Four different polymorphic conformations of diethyl 5,5'-[5,5'-[2,5-bis(2-ethylhexyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl]bis(thiophene-5,2-diyl)]difuran-2-carboxylate (DPP-(CF)2), namely, DPP-(CF)2-α, DPP-(CF)2-β, DPP-(CF)2-γ, and DPP-(CF)2-ω, were identified from X-ray diffraction analysis conducted on their thin films and single crystals. Highly crystalline and well-textured thin films of these four polymorphs were successfully prepared via postgrowth solvent vapor and thermal annealing treatments to investigate the polymorphic phase-dependent optical and electrical properties of DPP-(CF)2. Interestingly, during the phase transition from DPP-(CF)2-α to DPP-(CF)2-ω, the optical band gap decreases from 1.75 to 1.5 eV because of the enhanced π-π interaction between the neighboring molecules. Except for DPP-(CF)2-γ, the other three phases show ambipolar charge transport. Although DPP-(CF)2-β and DPP-(CF)2-γ exhibit a similar way of packing, a small increment in the π-π-stacking distance (0.006 Å) and twist conformation of the grafted electron-donating moieties of DPP-(CF)2-γ are found to reduce its hole mobility.
从其薄膜和单晶的 X 射线衍射分析中鉴定出二乙基 5,5'-[5,5'-[2,5-双(2-乙基己基)-3,6-二氧代-2,3,5,6-四氢吡咯并[3,4-c]吡咯-1,4-二基]双(噻吩-5,2-二基)]二呋喃-2-羧酸酯 (DPP-(CF)2) 的四种不同的多晶型构象，即 DPP-(CF)2-α、DPP-(CF)2-β、DPP-(CF)2-γ 和 DPP-(CF)2-ω。通过后生长溶剂蒸气和热退火处理成功制备了这四种多晶型的高结晶和高织构的薄膜，以研究 DPP-(CF)2 的多晶型相依赖的光学和电学性质。有趣的是，在从 DPP-(CF)2-α 到 DPP-(CF)2-ω 的相转变过程中，由于相邻分子之间的 π-π 相互作用增强，光学带隙从 1.75eV 降低到 1.5eV。除了 DPP-(CF)2-γ 之外，其他三种相都表现出双极性电荷输运。尽管 DPP-(CF)2-β 和 DPP-(CF)2-γ 表现出相似的堆积方式，但 DPP-(CF)2-γ 中接枝给电子部分的 π-π 堆积距离（0.006Å）和扭曲构象略有增加，导致其空穴迁移率降低。
