D-A窄带隙有机小分子半导体材料溶解性改造与光伏器件性能研究

The synthesis of organic semiconductor materials which dissolved in environmental friendly solvent is the fundamental driving force to processing the active layer of organic photovoltaic with low-cost and low-pollution methods. In present work, not only the solubility of organic semiconductor, but also the morphology between donor and acceptor materials are controlled through the introduction of ethylene oxide (EO) chains on D-A narrow-band-gap conjugated molecular, benefited from which high performance environment-friendly active layer is prepared. Specifically, the spectral absorption of organic semiconductor is guaranteed by the rational selection of donor and acceptor units on the conjugated backbone. Meanwhile, the solubility of organic molecular is modulated by the introduction of EO flexible chains. Especially, the morphology of active layer is controlled by the hydrophilic interaction between the EO chains on both donor and acceptor materials, as well as the self-assembly between EO chain and inorganic nano-particles, which is related to the exciton separation and charge transport. From computational simulation, the relationship between organic molecular structure and spectral absorption, as well as the relation between the EO chains and the intermolecular interaction are both discussed in depth. Eventually, the impact mechanism of molecular structure which combined D-A conjugated backbone with flexible chains to the material solubility, the active layer morphology and the photovoltaic performance is established. Furthermore, based on the optimization of device structure, high performance organic solar cell is prepared with environment-friendly solvent processing.

从分子结构设计出发，合成溶于环境友好型溶剂的有机半导体材料是实现光伏器件活性层制备低成本、低污染的根本方法。本项目通过在窄带隙D-A共轭有机分子上引入多聚氧化乙烯（EO）链，实现有机半导体给体材料的溶解性改造及其与受体材料的分子间排列形貌调控，制备环境友好型溶剂加工的高效率活性层材料。通过共轭主链给受体单元的合理设计实现半导体分子光谱吸收的保证；通过EO柔性链的修饰实现半导体分子溶解性的调控；通过给受体材料上EO链间的亲水作用、EO链与无机纳米粒子的自组装作用实现对活性层形貌及其对激子分离和载流子传输的调控；通过模拟计算分析，对有机分子构造与光谱吸收，EO链与分子间作用力及排列的关系进行深入的探讨。建立D-A共轭主链—柔性链的分子构造对材料溶解性能、活性层形貌、光伏性能的作用机制。在此基础上，结合器件结构优化，制备环境友好型溶剂加工的高效率有机太阳能电池。

该项目已在ACS Appl. Mater. Interfaces, Polym. Chem., Sol. Energy Mater. Sol. Cells, J. Phys. Chem. C等刊物上发表SCI论文11篇，其中影响因子大于3以上9篇。通过对主链结构单元、π桥、柔性侧链、取代基、末端基和第三单元结构的设计调控了有机半导体材料的溶解性能、能级、光学电学性能（Polymer 2015，J. Phys. Chem. C, 2015，RSC Adv. 2015，Chem. Res. Chin. Univ. 2017）。通过在共轭骨架中引入四氟苯等含氟结构，调控了有机半导体材料的光谱吸收范围、能级、载流子迁移率和器件效率，获得了材料的高开路电压，高结晶性和才稳定性，设计合成了氟化有机光伏材料（Polym. Chem. 2015，J. Phys. Chem. C 2016, Synthetic Metals 2017，Macromol. Rapid Commun. 2017）。制备了醇溶性共轭电解质界面材料，通过控制共轭聚电解质上极性基团的含量，通过调节小分子共轭电解质的共轭骨架，通过改变极性基团的不同连接顺序，达到了调控界面性能的作用，获得了有机太阳能电池的效率提升及其稳定性的增强（ACS Appl. Mater. Interfaces 2016，Sol. Energy Mater. Sol. Cells 2016，Phys. Chem. Chem. Phys., 2016）。