Self‐assembly of fullerene derivatives plays an important role in controlling photovoltaic performance of organic solar cells (OSCs). Herein, we have synthesized two covalently bonded phenyl substituted fullerene derivatives ‐N‐Mtheyl‐2‐[2,5‐bis(trifluoromethyl)phenyl] fullerenopyrrolidine (1) and N‐Methyl‐2‐[2,4bis(trifluoro‐methyl‐6‐methoxy)phenyl]fullerenopyrrolidine (2), which are employed as electron acceptors in OSCs. The self‐assembly of two aforementioned molecules were investigated in the binary solvent system of chloroform and methanol (1:1 volume ratio). Further, optical, electro‐chemical and micro‐structural properties of self assembled structures were also studied. It is found that the architecture of assembly is directed by the functional groupsatthe phenyl ring and solvent molecule. The molecule 1 possessing ‐CF3 group and the molecule 2 possessing additional ‐OMe group on fullerene unitform flowers and flakes like structures, respectively. The assembly structure of 1 gets converted from flower to disc like structure with the variation of solvent from methanol to hexane. The OSCs fabricated using molecule 1 and molecule 2 as acceptor with PTB7 donor showed a power conversion efficiency of 6.8 and 3.6%, respectively with high open circuit voltages of ∼0.8 V.

中文翻译：

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富勒烯的三氟甲基定向超分子自组装：合成，表征和光伏应用

富勒烯衍生物的自组装在控制有机太阳能电池（OSC）的光伏性能中起着重要作用。在这里，我们合成了两个共价键合的苯基取代的富勒烯衍生物-N-甲基-2- [2,5-双（三氟甲基）苯基]富勒吡咯烷（1）和N-甲基-2- [2,4双（三氟甲基） 6-甲氧基）苯基]富勒烯基吡咯烷（2），在OSC中用作电子受体。在氯仿和甲醇（1：1体积比）的二元溶剂系统中研究了上述两个分子的自组装。此外，还研究了自组装结构的光学，电化学和微观结构特性。发现组装的结构是由苯环和溶剂分子上的官能团指导的。在富勒烯单元上，具有-CF3基团的分子1和具有附加-OMe基团的分子2分别形成花朵和片状结构。1的组装结构随着溶剂从甲醇到己烷的变化而从花转变为盘状结构。使用分子1和分子2作为受主和PTB7供体制备的OSC的功率转换效率分别为6.8和3.6％，且开路电压约为0.8V。