物理化学学报 >> 2018, Vol. 34 >> Issue (11): 1239-1249.doi: 10.3866/PKU.WHXB201803272

所属专题: 庆祝李永舫院士七十华诞特刊

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氟化策略:高效有机光伏材料的设计与应用

邓丹,周二军*(),魏志祥*()   

  • 收稿日期:2018-02-23 发布日期:2018-04-17
  • 通讯作者: 周二军,魏志祥 E-mail:zhouej@nanoctr.cn;weizx@nanoctr.cn
  • 作者简介:周二军,研究员,出生于1980年。2007年在中国科学院化学研究所获得博士学位。2007年至2014年先后在日本科学技术振兴机构、日本东京大学、日本理化学研究所从事科学研究工作。2014年3月被聘为国家纳米科学中心研究员。主要从事有机光电材料的设计合成及器件研究|魏志祥,研究员,出生于1975年。2003年在中国科学院化学研究所获得博士学位。2003年至2005年,先后在德国马普胶体界面研究所和加拿大多伦多大学从事博士后研究;2006被聘为国家纳米科学中心研究员。主要研究方向为有机光电材料的自组装和柔性器件
  • 基金资助:
    国家自然科学基金(51603051);国家自然科学基金(21125420);中国科学院青年创新促进会资助项目

Fluorination: An Effective Molecular Design Strategy for Efficient Photovoltaic Materials

Dan DENG,Erjun ZHOU*(),Zhixiang WEI*()   

  • Received:2018-02-23 Published:2018-04-17
  • Contact: Erjun ZHOU,Zhixiang WEI E-mail:zhouej@nanoctr.cn;weizx@nanoctr.cn
  • Supported by:
    the National Natural Science Foundation of China(51603051);the National Natural Science Foundation of China(21125420);the Youth Innovation Promotion Association CAS

摘要:

有机太阳能电池具有成本低廉、质量轻、柔性可折叠以及可以大面积印刷等优点,受到广泛关注。但与无机太阳能电池相比,其能量损失较高。在有机光伏分子中引入氟原子是一种有效提高器件性能的分子设计策略。本文从氟原子特点出发,总结了氟化给体、π桥和受体单元对分子能级调控和形貌优化的作用,阐明了氟原子降低能量损失的内在原因;并通过代表性分子设计实例,简要阐述了氟化策略在高效聚合物给体材料、高效可溶性小分子给体材料以及高效非富勒烯受体材料中的应用;最后,对氟化策略的应用进行了总结,并展望了未来的研究方向。

关键词: 氟化, 能级, 形貌, 能量损失, 光电转换效率

Abstract:

Organic solar cells (OSCs) have received widespread attention for their advantages of cheap, light, flexible characteristics and roll-to-roll printing technology. However, the efficiencies of OSCs are still lower than 50% of the theoretical Shockley-Queisser detailed-balance efficiency limit. Consequently, to further improve device performance, it is significant to develop molecular design strategies to lower the energy loss and enhance the utilization of absorbed photons. From the molecular design aspects, down-shifting energy levels is an effective way to lowering the energy loss in order to obtain a high open circuit voltage, and optimizing the morphology is an efficient approach to lowering the fill factor and current density loss. Introduction of fluorine atom in molecules is an effective molecular design strategy to realize both above-mentioned requirements. In this review, starting from the characteristics of fluorine atoms, we summarized the fluorination effects on adjusting molecular levels. Whether the fluorine attached to the donor units, acceptor units or π-bridge units, it could efficiently downshift the energy levels. However, fluorinating the molecular backbone affects the energy levels more significantly than fluorinating the side chains of the two-dimensional structures. The introduction of fluorine is also an effective approach to optimize molecular packing and morphology. Generally, whether the fluorine attached to the donor units, acceptor units or π-bridge units, it can effectively increase molecular coherence length, decrease ππ stacking distance, and enhance domain purity. However, there is a saturation of the fluorine on the backbone, further introduction of the fluorine can accelerate molecular aggregation and induce disorder. In addition, the position of fluorination is important. In this review, we also briefly discuss the fluorination strategy for representative and high-efficiency photovoltaic material designs, including small molecule, polymer, and non-fullerene OSCs, mainly focusing on improving efficiency by reducing the efficiency losses. Fluorination is advantageous only for OSCs with high HOMO energy levels or poor molecular packing; otherwise, it can compromise device performance. OSCs based on narrow band-gap non-fullerene acceptors with low energy loss show promise for highly efficient device performance. Fluorination provides an effective means to fine-tune energy levels and form ideal microstructures to further reduce the efficiency loss and achieve a breakthrough in device performance.

Key words: Fluorination, Energy level, Morphology, Energy loss, Power conversion efficiency

MSC2000: 

  • O646