α-八甲基取代金属酞菁及聚噻吩复合材料设计合成与光伏性能研究

Planar molecular structure plays an important role where the molecules can self-assemble and stack well to exhibit better intermolecular interaction. The high chemical stability and wide sun spectrum absorbance distinguish planar metal phthalocyanine (M-Pc) and Poly(3-hexylthiophene) (P3HT) molecules from other high mobility organic semiconductors and stimulate research on improving semiconducting properties and application of organic electronics devices. It is the first time to propose nanocomposite materials made of α-octamethyl metal phthalocyanine nanocrystals and P3HT which can lead to high performance ternary organic photovoltaic cells using solution spin coating process. Alkyl functional groups having self-organizing nature of organic molecules can act as the driving force for molecular ordering in the solid state. Preliminary results from our group show that methyl groups render different molecular alignment of the semiconducting core to orient differently, thereby change the physical properties of their solid thin films. In this project we propose to synthesize metal Pc molecules with α-octamethyl substituent and study the physical properties at their solid state. Methyl substitutents not only increase the π-π interaction of Pc molecules and charge carrier mobility, but also lead to formation of nanocrystals under vacuum sublimation. We will employ phthalocyanine nanocrystals with different weight ratios in P3HT polymer for fabrication of nanocomposite and examine the respective organic photovoltaic cell performance. The formation of an organic/organic composite has many advantages, which include increasing charge carrier mobility, energy level matching, wider range absorption of the visible solar spectrum and a simple solution process technique for device fabrication. In the same time, different metal ions (Cu, Zn, Pd and Pt) will be incorporated in phthalocyanine to study the influence of metal ions on the carrier mobility, absorption of the visible solar spectrum, exciton diffusion length of composite, and its relationship with performance of photovoltaic cells. This research mainly focuses on the analysis of the structure-property relationship of various methyl substituted metal phthalocyanine for the design and development of phthalocyanine/P3HT nanocomposite materials for high performance ternary bulk heterojunction photovoltaic devices.

有机半导体材料载流子迁移率低，吸光效率不高及激子扩散距离短限制了其在光电转换领域的应用。近年来，酞菁/高聚物复合材料对提高有机半导体光电性能发挥着重要的作用。本项目就不同α-八甲基取代金属酞菁对聚噻吩复合材料光电特性的影响进行研究，主要内容包括：设计合成一系列新型α-八甲基取代金属酞菁，制备酞菁纳米晶/聚噻吩复合材料，并研究其在体异质结太阳能电池的光伏特性。通过在酞菁环α位上进行八甲基取代和酞菁环中心引入不同的正二价金属离子（Cu、Zn、Pd、Pt），改变金属离子对酞菁环排列的影响方式。研究不同金属-甲基和金属-金属间相互作用对酞菁环平面性，酞菁分子间的π-π堆积方式，及酞菁纳米晶物理、化学、半导体特性的影响。探索不同酞菁分子结构对复合材料载流子迁移速率、吸收光谱、激子扩散长度的提高，以及和光伏器件光电转换效率之间的关系。总结内在联系规律，实现高性能的有机光伏电池。

迄今为止能源作为社会和经济发展的重要基础条件，仍然主要依赖于化石能源。而使用化石能源带来的环境污染、雾霾气候和温室效应已经严重威胁人类社会的可持续发展，同时作为不可再生能源，化石能源也终究会枯竭。太阳电池将太阳能直接转化为电能，可以为人类社会发展提供取之不尽用之不竭的清洁能源，是人类社会应对能源危机，解决日益严峻的环境问题，寻求可持续发展的重要对策。因此，探索开发更廉价的高效太阳电池成为近年科研工作的热点。有机太阳能电池及钙钛矿太阳电池作为新一代光伏器件具有广阔应用前景。酞菁（Pc）是四氮大环配体的重要种类，具有高度pi-共轭体系，合成简单，具有良好的热、化学稳定性和优良的光电性能。本项目通过合成一系列新型八甲基取代金属酞菁，研究金属酞菁分子在八甲基及不同中心金属离子取代后对分子成膜及形成纳米晶的影响，重点探索不同酞菁分子结构对固体形态（薄膜与纳米晶）物理、化学以及半导体特性的影响，包括对载流子迁移速率、吸收光谱以及其在有机光伏电池及钙钛矿电池中应用性能的影响。研究对比发现，与无取代金属酞菁相比，八甲基取代金属酞菁在成膜后可以形成从edge-to-edge的分子堆积到face-to-face的分子堆积转变，从而在二极管结构获得更高的载流子迁移率。同时八甲基的引入有利于提高酞菁成膜后的疏水性，在钙钛矿电池中的应用有利于形成封装效果，提高器件光电转换效率与稳定性，相关器件光电转换效率可达到16%以上，器件寿命达到2000小时以上。八甲基取代酞菁还有利于形成更强分子堆积，易于制备纳米晶结构，分散于溶剂可形成电子墨水从而实现液相旋涂工艺制备高性能晶体管器件。其纳米晶与聚噻吩材料形成复合材料制备有机光伏电池，器件光电效率可达到8%以上。有关核心材料的研发，对于抢占太阳电池行业发展的先机，促进太阳电池技术的升级换代具有重要意义。