高效可溶液加工卟啉小分子有机太阳电池的研究

Solution processed organic solar cells (OSCs) have attracted extensive attention due to the advantages of light weight, flexible and simple preparation including spin-coating, inkjet-printing and fast/cheap roll-to-roll production et al. Small molecules for solution processed bulk heterojunction (BHJ) OSCs are very attractive for several advantages such as defined molecular structure and molecular weight, high purity, and less batch-to-batch variations superior to their polymer counterparts, thus showing a very promising future in large-scale OSC applications. As the derivatives of chlorophylls, porphyrins and their derivatives have great potential in organic photovoltaic (OPV) studies and applications, but the reported power conversion efficiencies (PCEs) of the OSCs based on these materials usually were very low. We analyzed the factors which effect the PCEs of the OSCs based on porphyrin active materials reported previously, and in this project we will design and synthesize π-conjugated donor-acceptor (D-A) porphyrin small molecules by simultaneously introducing electron-withdrawing units and acetylene bonds between porphyrin unit and the acceptor units to make the acceptor unites conjugated to the porphyrin unit and therefore to expand the π-conjugation of the whole molecules, tune the optical bandgaps and energy levels, and facilitate the intramolecular charge transfer. We will also intensify the absorption of the conjugated D-A porphyrins to absorb more light, and modify the substituents at a porphyrin unit or its acceptor units to optimize the solubility and the intermolecular self-assembly to improve the intermolecular charge transportation in film. By taking the advantage that a free-base porphyrin is able to coordinate with different metal ions, we will also synthesize different metalloporphyrin complexes to explore the relationship between the OPV properties and the metal ions to further improve the PCEs of the OPV devices based on these solution-processable porphyrin small molecules. We hope to disclose the principles how to design high performance porphyrin OPV materials from several aspects of molecular designs. From the point of device optimization, we will also optimize the morphology of the bulk heterojunction, the structures of the OPV devices and the characters of the multi-interlayers to achieve high efficient charge separation, charge transportation and charge collection to further enhance the performance of the solution processed BHJ OSCs.In brief, by simultaneously optimizing the chemical structures of the porphyrin OPV materials and the engineering of the OPV devices, we will achieve high performance OPV materials and devices and make contributions to the basic studies on OSCs and their applications in future.

溶液加工有机太阳电池(OSCs)具有质轻、适应性好和可印刷等优点，其研究是近几年来的国际热点之一。与聚合物相比，有机小分子具有确定的分子式和分子量、更容易被纯化和各批次的差异小等优点，因此在溶液加工OSCs应用方面更具潜力。卟啉的化学结构与叶绿素相似，但目前报道的基于卟啉及其衍生物OSCs的能量转换效率普遍偏低。本项目分析了影响基于卟啉活性材料的太阳电池性能的因素，提出了设计和合成共轭给-受体卟啉分子体系以提高分子内电荷迁移的分子设计思路，再通过改善薄膜状态下分子之间的自组装及形貌以提高分子间的电荷传输、通过调控材料对光的吸收以及研究不同的金属离子对卟啉配合物的光电性能影响等，进一步提高材料的光电性能，揭示高效卟啉小分子溶液加工OSCs材料的分子设计规律；最后通过对光伏器件进行优化，获得高能量转换效率的小分子OSCs材料和器件，为OSCs的基础研究和未来的应用研究做出贡献。

人类对太阳能这种清洁能源的开发利用日益迫切，有机太阳电池（OSCs）由于有机材料的化学结构几乎无穷、器件质轻、适应性好、可溶液加工和能制备大面积柔性器件等优点而倍受人们的关注，其研究是国际上近年来发展最快和最具活力的研究领域之一。与聚合物相比，有机小分子具有确定的分子式和分子量、更容易被纯化和各批次的差异小等优点，因此在溶液加工OSCs应用方面具有很大的潜力。.卟啉的化学结构与叶绿素相似，但以前报道的基于卟啉及其衍生物OSCs的能量转换效率偏低。为了提高这一类太阳电池器件的效率，本项目从材料的设计合成以及器件的表征和优化两方面全面开展研究工作。通过对分子侧链的调控，获得了能量损失只有0.59V但是能量转换效率达到8.08%的太阳电池。创新性地使用吡啶添加剂制备太阳电池，使用双添加剂调控活性层薄膜形貌，不仅将电池的光电转换效率提高到了9.06 %，而且通过系统的研究发现：吡啶添加剂可以提高卟啉给体材料和富勒烯衍生物受体材料的互溶程度，为进一步器件与形貌优化提供了巨大空间；通过对共轭主链的调控，合成了新型的双卟啉给体材料，相关材料的二元太阳电池器件的能量转换效率超过10%；由于我们合成的单卟啉和双卟啉电池给体材料具有强近红外吸收，相关太阳电池在近红外区具有高外量子效率等优势，我们系统进行了三元电池和叠层电池的研制。卟啉/聚合物PTB7/PCBM以及卟啉/小分子/PCBM两种三元电池的能量转换效率都超过11%。使用卟啉小分子与其它小分子或聚合物材料构建的叠层电池都表现出高的PCE，其中最高的PCE达12.50%，这是论文发表时体异质结有机太阳电池国际最高效率。.我们的研究将基于卟啉类材料的太阳电池推进到了一个新高度，不仅丰富了有机太阳电池材料体系，而且取得了国际领先的能量转换效率，国际上多个研究小组跟进了我们的研究工作。另外，由于我们设计合成的卟啉类光电材料具有高的摩尔消光系数，具有高迁移率，具有很好的近红外吸收，所以在有机近红外光研究领域也可能具有重要应用前景。