Synthesis and photovoltaic properties of low bandgap dimeric perylene diimide based non-fullerene acceptors
作者:Xin Zhang、Jiannian Yao、Chuanlang Zhan
DOI:10.1007/s11426-015-5485-8
日期:2016.2
Non-fullerene organic acceptors have attracted increasing attention in recent years. One of the challenges in the synthesis of non-fullerene organic acceptors is to tune the absorption spectrum and molecular frontier orbitals, affording low bandgap molecules with improved absorption of the near-infrared solar photons. In this paper, we present the synthesis, optoelectronic and photovoltaic properties of a series of dimeric perylene diimide (PDI) based non-fullerene acceptors. These PDI dimers are bridged by oligothiophene (T) from 1T to 6T. With the increase of the oligothienyl size, the highest occupied molecular orbital (HOMO) energy is raised from −5.65 to −5.10 eV, while that of the lowest unoccupied molecular orbit (LUMO) is kept constant at −3.84 eV, affording narrow bandgap from 1.81 to 1.26 eV. The absorption from the oligothiophene occurs between 350 and 500 nm, which is complementary to that from its bridged PDI units, leading to a wide spectral coverage from 350 to 850 nm. The optimal dihedral angle between the bridged two perylene planes is dependent on the oligothienyl size, varying from 5° to 30°. The solubility of the dimers depends on the oligothienyl size and can be tuned by the alkyl chains on the bridged thienyl units. The possible applications as the solution-processable non-fullerene organic acceptor is primarily studied using commercial P3HT as the blend donor. The photovoltaic results indicate that 1T, 4T and 6T all yield a higher efficiency of ∼1.2%, whereas 2T, 3T and 5T all give a lower efficiency of <0.5%. The difference in the cell performance is related with the tradeoff between the differences of absorption, HOMO level and film-morphology between these dimers.
近年来,非富勒烯有机受体越来越受到关注。合成非富勒烯有机受体的挑战之一是如何调整吸收光谱和分子前沿轨道,从而获得对近红外太阳光子有更好吸收的低带隙分子。在本文中,我们介绍了一系列基于二聚过二亚胺(PDI)的非富勒烯受体的合成、光电和光伏特性。这些 PDI 二聚体由 1T 到 6T 的低聚噻吩(T)桥接。随着低聚噻吩尺寸的增加,最高占位分子轨道(HOMO)的能量从 -5.65 eV 上升到 -5.10 eV,而最低未占位分子轨道(LUMO)的能量则保持在 -3.84 eV 不变,从而产生了从 1.81 到 1.26 eV 的窄带隙。低聚噻吩的吸收发生在 350 纳米到 500 纳米之间,与桥接 PDI 单元的吸收互补,从而产生了 350 纳米到 850 纳米的宽光谱覆盖范围。桥接的两个苝平面之间的最佳二面角取决于低聚噻吩的大小,从 5°到 30°不等。二聚体的溶解度取决于低聚噻吩基的大小,并可通过桥接噻吩基单元上的烷基链进行调整。我们主要以商用 P3HT 作为混合供体,研究了其作为可溶液加工的非富勒烯有机受体的应用可能性。光伏研究结果表明,1T、4T 和 6T 的效率均高于 1.2%,而 2T、3T 和 5T 的效率则低于 0.5%。电池性能的差异与这些二聚体之间的吸收、HOMO 水平和薄膜形态差异之间的权衡有关。