基于非平面稠环苝酰亚胺的全聚合物太阳能电池

All-Polymer Solar Cells Based on Acceptors Containing Non-Planar Fused Perylene Diimide

将一种具有扭曲结构的稠环苝酰亚胺单元(FPDI-Th)和二氟苯并噻二唑(DFBT)作为单体,并在两者之间插入带有不同烷基侧链的噻吩作为桥接单元,合成了两种新的聚合物受体PPDIBT-Th与PPDIBT-Th-C6,并将其用于全聚合物太阳能电池器件。研究了烷基侧链对聚合物性质和有机太阳能电池(OSCs)器件性能的影响。结果表明:基于这两种聚合物的OSCs器件都展示了优异的光伏性能,烷基侧链的引入不仅会影响分子自身的堆积,还会影响与其共混的聚合物的固态堆积。引入适量的烷基侧链有利于活性层的整体形貌达到较好的平衡状态,提升光伏器件的性能。虽然PPDIBT-Th-C6自身分子间堆积变弱,但是PPDIBT-Th-C6和聚合物给体共混成膜之后,有效保证了给体的固态堆积,最终获得了更大的光电流(12.15 mA/cm^2)与光电转换效率(4.95%)。

Based on a non-planar fused perylene diimide unit(FPDI-Th),a new class of polymers,PPDIBT-Th and PPDIBT-Th-C6,were designed and synthesized,and they were served as acceptors for application in all-polymer solar cells.Compared to PPDIBT-Th,hexyl side chain was introduced into PPDIBT-Th-C6 to tune the molecular conformation.These two polymers as well as the fabrication and measurement of all-polymer solar cell devices were systematically studied by nuclear magnetic resonance(NMR),gel permeation chromatography(GPC),UV-Vis absorption and cyclic voltammetry(CV).Both of devices blending PPDIBT-Th or PPDIBT-Th-C6 with polymer donor PTB7-Th show good photovoltaic performances,indicating that the polymers contained FPDI-Th are promising acceptors for all-polymer solar cells.In addition,the introduction of side chains into the polymers decreases the planarity of the backbones,leading to a weaker molecular packing and absorption intensity.However,the side chains not only affect the properties of acceptor itself but also tune the molecular packing of polymer donor that is another component in bulk heterojunction(BHJ).In the blend film,PPDIBT-Th with strong intermolecular interaction inhibits the aggregation of donor PTB7-Th,leading to an inferior morphology which has been verified by the device performances and atomic force microscopy(AFM)characterization.Due to the balance between miscibility and crystallinity,all-polymer solar cells based on PPDIBT-Th-C6 and PTB7-Th display a higher shortcircuit current density(Jsc)of 12.15 mA/cm^2,eventually achieving a superior power conversion efficiency(PCE)of 4.95%.