物理化学学报 >> 2019, Vol. 35 >> Issue (1): 76-83.doi: 10.3866/PKU.WHXB201712063

所属专题: 非富勒烯有机太阳能电池

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A-D-A型小分子电子给体光伏材料的端基修饰及其光伏性能

贾国骁1,张少青1,*(),杨丽燕2,何畅2,范慧俐1,*(),侯剑辉1,2,*()   

  1. 1 北京科技大学化学与生物工程学院,北京 100083
    2 高分子物理与化学国家重点实验室,北京分子科学国家实验室,中国科学院化学研究所,北京 100190
  • 收稿日期:2017-11-08 发布日期:2018-06-13
  • 通讯作者: 张少青,范慧俐,侯剑辉 E-mail:shaoqingz@iccas.ac.cn;fanhl@sas.ustb.edu.cn;hjhzlz@iccas.ac.cn
  • 基金资助:
    国家自然科学基金(2170040201);国家科技重大专项(2016YFC0700603);中央高校基本科研业务费专项资金(FRF-TP-17-009A1)

Development of Benzodithiophene-Based A-D-A Small Molecules with Different Acceptor End Groups for Efficient Organic Solar Cells

Guoxiao JIA1,Shaoqing ZHANG1,*(),Liyan YANG2,Chang HE2,Huili FAN1,*(),Jianhui HOU1,2,*()   

  1. 1 School of Chemical and Biological Engineering, University of Science and Technology Beijing, Beijing 100083, P. R. China
    2 State Key Laboratory of Polymer Physics and Chemistry, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
  • Received:2017-11-08 Published:2018-06-13
  • Contact: Shaoqing ZHANG,Huili FAN,Jianhui HOU E-mail:shaoqingz@iccas.ac.cn;fanhl@sas.ustb.edu.cn;hjhzlz@iccas.ac.cn
  • Supported by:
    National Natural Science Foundation of China(2170040201);National Science and Technology Major Project of the Ministry of Science and Technology of China(2016YFC0700603);the Fundamental Research Funds for the Central Universities, China(FRF-TP-17-009A1)

摘要:

有机太阳能电池(OSCs)活性层中的给体材料主要包括共轭聚合物与有机小分子,由于有机小分子给体具有结构确定、易于提纯、重复性高等独特的优势,近年来受到研究工作者的广泛关注。本工作中,我们采取具有良好共平面性的三联苯并二噻吩(TriBDT-T)为推电子(D)中心共轭单元,分别以罗丹宁(RN)、氰基罗丹宁(RCN)和1, 3-茚二酮(IDO)为拉电子(A)共轭端基,设计并合成了三种具有A-D-A型结构的小分子给体材料TriBDT-T-RN、TriBDT-T-RCN和TriBDT-T-IDO。我们对比研究了三种端基对其热分解温度、吸收光谱和分子能级等基本性能的影响,并分别将三种小分子给体与非富勒烯型受体材料IT-4F共混制备器件,详细研究了活性层形貌与光伏性能之间的关系。结果表明,不同的A型端基对小分子给体材料的光学性能、电化学性能、光伏器件中活性层的微观形貌以及能量转换效率(PCE)产生显著影响。基于TriBDT-T-RN:IT-4F、TriBDT-T-RCN:IT-4F和TriBDT-T-IDO:IT-4F的光伏器件的能量转换效率分别为9.25%、6.31%和6.18%。

关键词: 小分子给体, 端基修饰, 有机太阳能电池, 非富勒烯受体, A-D-A结构

Abstract:

In recent years, organic solar cells (OSCs) have attracted increasing attention, and the power conversion efficiency (PCE) of OSCs has markedly improved. To enhance the photovoltaic properties of OSCs, it is important to develop the donor materials in the light-harvesting layer, which mainly include conjugated polymers and small molecules (SMs). Compared with polymeric materials, small-molecule materials have been widely investigated for their superior characteristics, such as well-defined molecular structures that can provide good batch-to-batch reproducibility. In this work, we synthesized three SM donor materials with theacceptor-donor-acceptor (A-D-A) structure by employing the trialkylthienyl-substituted benzodithiophene (TriBDT-T) unit as the D-core unit, and rhodanine (RN), cyano-rhodanine (RCN), and 1, 3-indanone (IDO) as the A end groups, respectively. The optical properties, molecular energy levels, and thermogravimetic characteristics of the three SMs were studied; moreover, the blend morphologies and photovoltaic properties of the devices by employing the non-fullerene (NF) acceptor, IT-4F, were systematically investigated. The results showed that 1) the three SMs exhibit good thermal stabilities as evinced by thermogravimetric analysis (TGA), and all decomposition temperatures exceeded 410 ℃; 2) They all exhibit strong and broad absorption in the visible light range (300–700 nm), and show similar molar extinction coefficients; 3) the HOMO levels are -5.47 eV, -5.54 eV, and -5.44 eV for RN, RCN, and IDO, respectively, implying the clear influence of the different end groups for the energy levels of the A-D-A-type SMs; the slight differences in the optical and electrochemical properties of the corresponding donor material could be attributed to the different electron-withdrawing ability of the A-type end groups. When studying the photovoltaic properties, interestingly, the RN:IT-4F blend was found to form fibrillar-like aggregates with appropriate size, and the corresponding devices exhibited desirable short circuit current (Jsc) and thus the highest PCE value of 9.25%; however, large-size aggregates were formed in the RCN:IT-4F and IDO:IT-4F blend films, resulting in a much lower Jsc and fill factor (FF), and the PCE of the corresponding devices were only around 6%. In summary, by introducing RN, RCN, and IDO as the A units, we synthesized a class of TriBDT-T based A-D-A type SMs. This study shows that terminal A units exert influence on the absorption spectra, molecular energy level, and morphologies after blending with the acceptor material, and hence, the corresponding devices exhibit significant differences in photovoltaic performance. This work also provides useful information for the molecular design of SM donor materials.

Key words: Small molecule donor, Terminal modification, Organic solar cells, Non-fullerene acceptor, Acceptor-Donor-Acceptor structure

MSC2000: 

  • O646