基于苝二酰亚胺类非富勒烯受体共混体系凝聚态结构调控

Morphology Control of Non-fullerene Blend Systems Based on Perylene Diimide Acceptors

非富勒烯太阳能电池具有给受体能级可调、吸收范围宽及可溶液加工等优势,已经成为太阳能电池领域发展趋势。在高性能材料开发及器件结构优化的推动下,能量转换效率已经突破11%。其中,苝二酰亚胺(PDI)类分子价格低廉且具有良好的稳定性及较高的电子迁移率,已经发展成为重要的非富勒烯受体材料。然而,PDI类材料刚性稠环结构使得分子间具有强烈的π–π相互作用(受体–受体分子间及给体–受体分子间),导致共混体系相分离尺寸可控性差,给受体分子间共混程度难于调控,从而发生严重的成对以及非成对电荷复合。本文从分子间作用力入手(溶剂–溶质、给体–受体分子间作用力)详述了非富勒烯共混体系相分离结构、相区尺寸及共混相含量调节的相关原理及方法。研究表明基于PDI共混体系,固–液相分离及分子扩散能力是决定相分离结构的本质因素,通过调控给受体比例及热退火温度实现了孤岛及互穿网络结构的构筑。同时,通过平衡受体分子间π–π作用及给受体间电荷转移,实现了低相容性及高相容性共混体系相区尺寸的可控调节。在此基础上,利用添加剂手段通过调节溶剂与溶质分子间的溶度参数差值,实现了薄膜内共混相的可控调节,并针对具有不同相容性共混体系给出了添加剂的选择原则。

In recent years, the development of perylene diimide derivative （PDI）-based non-fullerene organic solar cells has been extensively studied. These solar cells exhibit unique advantages such as complementary light absorption, tunable energy levels, excellent electron transport properties, and relatively low cost. However, the strong π-π stacking between the PDI molecules tends to induce an uncontrolled phase separation structure, large domain size, and anunmanageable mixed phase, leading to severe geminate and non-geminate recombination and restriction of the final power conversion efficiency of the non-fullerene-based systems. In this work, it was found that one of the most important parameters that helps regulate phase structure is the molecular diffusion rate. By tuning the thermal annealing and liquid- solid phase separation and blend ratio, the phase-separated structure could be adjusted. Further, the domain size of blend systems with different compatibilities was regulated by balancing the Tr--Tr and charge transfer interactions. In addition, the amount of the intermixed phase was controlled by tuning the solubility parameter difference （AS） between the solvent and the solute.