联受体型聚合物光伏材料的能级调控和器件性能研究

The power conversion efficiency of photovoltaic devices based on donor-acceptor type conjugated polymers gained obvious breakthrough in recent years. Compared with silicon-based photovoltaic devices, the performance and stability of polymer solar cells is really not high enough for product exploit and commercial application, which need to be optimized from both materials and devices.In order to improve the efficiency and stability, the structure of conjugated polymers should be optimized, such as improving the energy levels and absorption ability.Specially,improving the device photochemical stability via lowering the highest occupied molecular orbital (HOMO) level under the premise of ensuring high efficiecy is very important.Based on the above considerations,the polymers with low HOMO level are chosen as subject, and the linked-acceptors units will be introuduced to polymer mainchain: firstly, this higher density of acceptor structure can furtherly lower the HOMO level of the polymer which can increase the open circuit voltage and stability of devices; secondly,combined with the result of theoretical calculation, the linked-acceptors can hopefully improve the absorption coefficiency and then improve the absorption ability of the materials.Thus, this strategy is predicated as an efficient way to design and synthesize high power conversion efficiency and high air stability photovoltaic polymer materials.

基于给-受结构的聚合物本体异质结的光伏器件的光电转换效率近年来取得重大突破。但是相比于硅基太阳能电池，当前这种聚合物太阳能电池的光电转换效率和稳定性依然不能达到产品开发和商品化应用的要求。这就需要从光伏材料入手，对材料-器件进行全面的探索和优化。从材料的角度出发，为了进一步提高光电转换效率和稳定性，我们需要针对给-受型共轭聚合物的特点进行优化，如通过改变分子结构来调节能级结构和光吸收能力。特别是适当降低最高占据轨道(HOMO)能级来提高光化学稳定性，同时保证高的光电转换效率。基于以上考虑，我们将联受体引入具有低HOMO能级的给-受结构的聚合物主链中：一方面提高受体浓度，进一步适当降低材料的HOMO能级以提高器件的开路电压和光化学稳定性；另一方面，结合理论计算结果，联受体单元有望提高聚合物的摩尔吸光系数从而提高材料的吸光能力。这个策略预计是设计具有高效率和高空气稳定性的光伏材料的有效途径。

为了进一步提高有机光伏的光电转换效率，针对给-受型共轭聚合物的特点进行优化，通过改变分子结构来调节能级结构和光吸收能力。特别是适当降低最高占据轨道(HOMO)能级来提高器件的开路电压，同时保证高的光电转换效率。从材料的角度出发，选取具有低HOMO 能级的给-受结构的聚合物为研究主体，将联受体单元引入聚合物主链中，设计合成了一系列联受体型聚合物和小分子有机光伏材料，有效地降低了HOMO能级，获得了高Voc的光伏器件，更进一步地提高了材料的摩尔吸光系数，从而提高了器件效率；同时将联受体型的聚合物或小分子引入到三元体系中，通过形貌优化，可进一步提高性能。.通过上述研究，完成了项目申请时提出的目标，并产生了一些新的值得可持续研究问题和方向。本项目协助培养博士研究生4名，在J. Am. Chem. Soc., Adv. Mater., Adv. Energy Mater., Adv. Sci.等高影响期刊上共发表论文23篇，研究成果被Materials Views等科技媒体报道。