A series of novel wide bandgap small molecules(IFT-ECA, IFT-M, IFT-TH and IFT-IC) based on the A-D-A structure with indenofluorene core, thiophene bridge, and different electron-deficient end-capping groups, were synthesized and used as non-fullerene acceptors in organic solar cells. The influences of end-capping groups on the device performance were studied.The four materials exhibited different physical and chemical properties due to the variation of end-capping groups, which further affect the exciton dissociation, charge transport, morphology of the bulk-heterojunction films and device performance. Among them, IFT-IC-based device delivered the best power conversion efficiency of 7.16% due to proper nano-scale phase separation morphology and high electron mobility, while the devices based on the other acceptors achieved lower device performance(4.14% for IFT-TH, <1% for IFT-ECA and IFT-M). Our results indicate the importance of choosing suitable electron-withdrawing groups to construct high-performance non-fullerene acceptors based on A-D-A motif.
Jianchao JiaNannan ZhengZhenfeng WangYunping HuangChunhui DuanFei HuangYong Cao
Compositing gold nanoparticles into conjugated molecules have been developed to be one of the most important approaches to increase stability, since degradation of conjugated materials is now one of the biggest bottle-necks to be conquered before industrialization application. Big-size colloidal gold nanoparticles with strong surface plasma resonance are designed to composite with conjugated molecules, in order to realize effective fluorescence enhancement and stabilization. The uniform composition film of hydrophilic colloidal gold nanoparticles (particle diameter of 30 nm) and hydrophobic carbazole functionalized fluorene trimers has been obtained by direct mixing of their aqueous and THF solutions, which is determined by AFM. By the comparison of composition based on fluorene trimers with similar structures, we have found that peripheral carbazole group and molecular size of fluorene trimers play an important role in the balance of incompatible solubility, which is regarded as increasing solubility of fluorene trimers in mixed solvent, connecting AuNP and peripheral carbazole groups, and restraining aggregate of gold nanoparticle. This allows facile hydrophilic gold nanoparticle to disperse uniformly in hydrophobic-conjugated host. Our investigations show that fluorescence intensity of composition film is enhanced by 4 folds, and heat treatment (200°C for 4h) for the composition film does not induce the degradation of conjugated backbone without the appearance of low-energy emission band, demonstrating the prominent potency of gold nanoparticles in enhanced fluorescence and stability of conjugated molecules and polymers.
Remarkable progress in high-performance polymer solar cells demonstrates their great potential for practical applications in the near future. Indeed, the power conversion efficiencies over 10% have been reported by many research groups, which are achieved through rational optimization of light-harvesting materials, interfaces and device processing technologies. In this mini review, we summarized the recent progress of highly efficient polymer solar cells, with specifically concern on successful strategies of rational molecular design of electron-donating and electron-accepting materials, elaborative interfacial engineering, and reasonable device architectures.
设计合成了Por-N,Por-NBr,Por-Cu-N和Por-Cu-NBr四种水醇溶性小分子卟啉衍生物.对这类卟啉小分子衍生物的紫外可见吸收光谱研究表明,基于金属铜配位的卟啉小分子衍生物较未配位化合物有微弱的蓝移.循环伏安法对这类小分子卟啉衍生物的研究表明,基于金属铜配合物的卟啉衍生物的最高占有分子轨道能级均没有明显变化.采用空间电荷限制电流方法对小分子卟啉衍生物的研究表明,基于金属铜配位的卟啉小分子衍生物的电子迁移率得到明显提高.以聚合物PCE10为给体材料,富勒烯衍生物PC71BM为受体材料,以及合成的小分子卟啉衍生物为阴极界面层制备了结构为ITO/PEDOT:PSS/PCE10:PC71BM/卟啉小分子衍生物/Al的聚合物太阳电池器件.器件研究结果表明,化合物Por-NBr,Por-Cu-N与Por-Cu-NBr作为电子传输层的器件的光电转换效率达到9%以上,其中以Por-Cu-N作为阴极界面层的器件达到的最高效率为9.12%,相应器件的短路电流密度,开路电压以及填充因子分别为16.91 m A·cm-2,0.79 V和68.1%.表明这类水醇溶性小分子卟啉衍生物作为聚合物太阳电池的阴极界面层有着广阔的应用前景.
