基于苝酰亚胺类铱配合物的设计合成及其光伏性能研究

Solution-processed bulk heterojuction organic solar cells (BHJ OSCs) taking the advantages of lightness, flexibility and low cost, have attracted much attention. In the past years, the power conversion efficiencies (PCEs) of BHJ OSCs increased very fast, mainly due to the intensive research on the development of novel donor materials. However, the progress in the development of novel acceptor materials is not so rapid. PC61BM, a fullerene-based material, takes the dominant position as the acceptor material in BHJ OSCs. However, the poor solar light absorption capability of PC61BM is an obvious drawback, which provides the opportunity for novel non-fullerene acceptor materials. In this project, we innovatively design a novel type of acceptor materials with a central Iridium core and perylene di-/monoimide ligands for solution-processed BHJ OSCs. Through rational molecular design, the aggregation mode of the rigid planar molecules has been changed and thus the unfavorable intermolecular states will be inhibited. The suitable balance between solubility and aggregation will be achieved, and the nanometer-scale morphology within the BHJ active film will be controllable so that the ideal microscopic phase separation will be realized. Furthermore, the acceptor materials we developed are phosphorescent molecular materials, which have longer exciton lifetime than these of used ones. The long exciton lifetime is beneficial to the separation and transport of the carriers, which is desirable to obtain a high short-circuit current and therefore the PCEs. This investigation will provide novel acceptor materials candidate, and will provide an approach toward higher efficiency in BHJ OSCs.

近几年来有机太阳能电池光电转化效率快速提升，主要是由于给体材料的密集研发，但受体材料的研发则相对薄弱。富勒烯衍生物PC61BM 作为有机太阳能电池中受体材料，占据了主导地位。但PC61BM 对可见光、近红外光的吸收能力低，为发展新型太阳能电池受体材料提供了机遇。本项目计划开发含有金属参与配位的溶液加工型的太阳能电池受体材料，发展一类新材料体系，在共轭体系中心位置引入重金属铱原子，发挥最大程度的位阻功能，改变刚性大平面分子的聚集模式，阻断激子弛豫形成分子间态这一电池不利因素；并有利于达到溶解-聚集能力的平衡，从而为调控太阳能电池活性层薄膜的纳米形貌，实现理想的微相分离提供可能。另外，本项目开发的磷光型受体材料，其激子寿命更长，更有利于载流子的分离和传输，期望得到高的短路电流，提高电池效率。本项目研究工作将为有机太阳能电池提供新型的受体候选材料，为实现更高光电转换效率提供一条新的途径。

苝酰亚胺类衍生物是一类性能优异的N-型有机半导体材料，但是由于苝酰亚胺分子之间很容易形成π-π堆积，而且当增大其共轭结构时，溶解性会变得更差，影响了其在有机电子学器件中的应用。为了解决其溶解性的难题，长的烷基链经常被引入到酰亚胺的亚胺基上，但是过长的烷基链将大大降低分子的电子迁移率。因此，本研究通过引入另一种策略——”局部共轭和整体扭曲“的方法来改善其溶解性，实现在不降低其电子迁移率的同时增加其溶剂性的功效，然后将其应用到有机太阳能电池器件中，实现了较高的太阳能电池器件效率，其中邻位-邻位偶联的苝酰亚胺二倍体实现了8.30%的能量转换效率，基本达到了目前国际上基于苝酰亚胺类受体材料的电池效率，有效地拓展了有机太阳能电池受体材料体系。