基于噻吩[3,4-c]并吡咯烷二酮新型受体的制备及其给体-受体共轭聚合物光伏性能研究

Thieno[3,4-c]pyrrole-4,6-dione (TPD) derivatives have attracted a lot of attention since they can lead to high-power conversion efficiencies when used as acceptors in donor-acceptor conjugated polymers in organic solar cells. However, the substituents at the imide position of TPD usually exhibit negligible affect on conjugation and electron-withdrawing capability because nodes in the HOMO and LUMO at the imide nitrogen reduce the coupling between the TPD unit and the imide substituents to a minimum. Herein we utilize the reaction of amino (NH2) and carbonyl (C=O) to generate imine. This project contains following three issues: (1) Fusing five-membered ring "imidazole" or six-membered ring "pyrimidine" to imide position of TPD. The conjugation and electron-withdrawing capability of TPD could be effectively tuned by changing fused aromatic heterocyclic compounds. (2) Synthesizing the D-A conjugated polymers based on modified TPD-based acceptors. The band gaps and HOMO and LUMO energy levels of the resulting D-A conjugated polymers could be tuned by donors and acceptors. (3) Increasing absorption of the D-A conjugated polymers in short wavelength region by introducing the conjugated substituents to side chains. In a word, we will optimize donors, TPD acceptors and side chains to tune the absorption and molecular energy levels to meet the requirements of an ideal donor toward highly efficient photovoltaic performance. These investigations will be beneficial to clarify the molecular energy levels control by D-A structures, and illustrate intramolecualr energy transfer and charge separation between donors and acceptors.This project will provide reference for organic photovotalic materials.

噻吩[3,4-c]并吡咯烷二酮（TPD）是一类新型高效的受体材料，其在D-A共轭聚合物和新型光伏材料中的应用正成为研究的热点。但是其电子云分布在酰亚胺的氮原子处存在节点，目前针对酰亚胺上的侧基的结构优化都不能实现对TPD受体的共轭性和吸电子性能的调节。本项目利用氨基（NH2）与羰基（C=O）反应生成亚胺（imine）的特性，采用二氨基化合物与3,4-噻吩二甲酸酐环化生成噻吩咪唑或噻吩嘧啶芳香杂环，首次调节TPD受体的共轭结构和吸电子性能；制备基于该新型受体的D-A共轭聚合物，通过调节给体和受体来优化D-A共轭聚合物的吸收特性和能级结构；并进一步在给体侧基上引入共轭基团增强D-A共轭聚合物在短波区的吸收，通过优化给体、TPD 受体和侧基实现D-A 共轭聚合物的吸收和能级结构最优化。本研究有益于揭示D-A结构对能级调控的规律，阐明分子内能量传递和电子转移过程，为新型光伏材料的结构设计提供基础。

本项目以噻吩[3,4-c]并吡咯烷二酮（thieno[3,4-c]pyrrole-4,6-dione, TPD）、吡咯并吡咯二酮（diketopyrrolopyrrole, DPP）和炔类有机光伏材料的设计合成和构效关系研究为主，探究分子结构与材料的光电性能、能级结构、聚集态结构以及光伏性能之间的关系，主要包含两部分工作：1、设计合成了一系列溶液加工的D-A-D，A-D-A和A′-D-A-D-A′结构的小分子光伏材料，系统研究了D-A结构对光电性能的影响；特别是利用透射电镜（TEM）、二维广角X射线衍射（GIWAXS）和共振软X射线衍射（RSoXS）深入研究了小分子光伏材料的结晶性能（尺寸、取向等）和本体异质结的聚集态形貌。研究发现，溶剂添加剂1,8-二碘辛烷（DIO）作用下A′-D-A-D-A′结构的小分子CNDPP表现出与聚合物不一样的结晶性能。DIO能同时增加CNDPP在(100)和(010)方向的结晶；然而DIO在增加聚合物(010)结晶的同时会减弱(100)的结晶。CNDPP:PC71BM体系光伏器件在DIO处理后光电转换效率达到近5%。2、合成了炔键连接的D-≡-A共聚物和金属铂炔有机小分子，研究了主链上引入炔键对材料光伏性能的影响。研究发现：炔键引入给体和受体间会使吸收发生蓝移，吸收范围变窄；吸电子的炔基会降低分子的HOMO能级，从而提高开路电压；炔键引入聚合物主链会增强分子的结晶，改变分子的结晶取向，聚合物择优face-on取向；但是炔类光伏材料和富勒烯本体异质结的相分离尺寸较大，导致炔类材料的短路电流和填充因子较低。通过以上研究，为更高效率光伏材料的结构设计和性能优化提供有益的实验数据。在该项目资助下共发表SCI学术论文7篇，申请中国专利1项。