Department of Applied Chemistry, Graduate School of Engineering, Osaka University , 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University , 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan.
ACS Appl Mater Interfaces. 2017 Nov 1;9(43):37702-37711. doi: 10.1021/acsami.7b10619. Epub 2017 Oct 23.
The shapes and lengths of the alkyl chains of conjugated polymers greatly affect the efficiencies of organic photovoltaic devices. This often results in a trade-off between solubility and self-organizing behavior; however, each material has specific optimal chains. Here we report on the effect of alkyl side chains on the film morphologies, crystallinities, and optoelectronic properties of new benzobisthiazole-naphthobisthiadiazole (PBBT-NTz) polymers. The power conversion efficiencies (PCEs) of linear-branched and all-branched polymers range from 2.5% to 6.6%; the variations in these PCEs are investigated by atomic force microscopy, two-dimensional X-ray diffraction (2D-GIXRD), and transient photoconductivity techniques. The best-performing linear-branched polymer, bearing dodecyl and decyltetradecyl chains (C12-DT), exhibits nanometer-scale fibers along with the highest crystallinity, comprising predominant edge-on and partial face-on orientations. This morphology leads to the highest photoconductivity and the longest carrier lifetime. These results highlight the importance of long alkyl chains for inducing intermolecular stacking, which is in contrast to observations made for analogous previously reported polymers.
共轭聚合物的支链形状和长度极大地影响了有机光伏器件的效率。这通常导致溶解性和自组织行为之间存在权衡取舍；然而，每种材料都有其特定的最佳链。在这里，我们报告了烷基侧链对新型苯并双噻唑-萘并双噻二唑（PBBT-NTz）聚合物的薄膜形态、结晶度和光电性能的影响。线性支化和全支化聚合物的功率转换效率（PCE）范围为 2.5%至 6.6%；通过原子力显微镜、二维 X 射线衍射（2D-GIXRD）和瞬态光电导技术研究了这些 PCE 的变化。性能最佳的线性支化聚合物，带有十二烷基和十四烷基癸基链（C12-DT），呈现纳米尺度的纤维，同时具有最高的结晶度，包括主要的边缘取向和部分面取向。这种形态导致了最高的光电导率和最长的载流子寿命。这些结果突出了长烷基链对于诱导分子间堆积的重要性，这与以前报道的类似聚合物的观察结果相反。
