烷基链支化位点对全稠环小分子受体聚集的影响

Effect of Alkyl-chain Branching Position on Molecular Aggregation of All-fused-ring Molecules

全稠环分子是一种具有优异稳定性的新型电子受体材料,可应用于有机太阳能电池.本文设计了2个具有不同吡咯单元上烷基链支化位点的全稠环小分子受体FM5与FM6,并研究了烷基链的支化位点对全稠环分子的光电性质和分子堆积性质的影响.与具有2号支化位点烷基链的FM5相比,具有3号支化位点烷基链的FM6展示出蓝移的吸收光谱和更高的结晶性.由于2号支化位点的烷基链具有更大的空间位阻,FM5在共混膜中表现出适宜的分子聚集行为,进而形成良好的共混膜形貌.将FM5作为受体制备有机太阳能电池器件,可以实现9.03%的能量转换效率,高于FM6(6.67%),这归因于合适的共混膜形貌.研究结果表明,侧链工程是调控全稠环分子聚集、结晶以及共混膜形貌的有效策略.

All-fused-ring molecules are a novel type of electron acceptor materials with excellent intrinsic stability for organic solar cell(OSC)applications.In this work,we developed two all-fused-ring small molecular acceptors,FM5 and FM6,with different branching positions of alkyl chains on the pyrrole motif.The effects of branching points of the alkyl chains on optical and electronic properties,molecular stacking of the molecules were investigated.Compared with FM5 with 2nd-position branched alkyl chains,FM6 with 3rd-position branched alkyl chains exhibits the blue-shifted absorption and higher crystallinity.Due to the large steric hindrance caused by alkyl chains at 2nd branching sites,FM5 exhibits appropriate molecular aggregation and thus favorable film morphology in the blend film.Due to the suitable blend film morphology,the OSC device using FM5 as electron acceptor exhibits a power conversion efficiency(PCE)of 9.03%,which is higher than that of FM6(6.67%).These results demonstrate that the side chain engineering is an effective strategy for tuning the molecular aggregation,crystalline and blend film morphology for all-fused-ring molecules.