利用表面结构控制无机量子点与有机共轭分子之间超快速电荷分离动力学过程的研究

Improving the charge separation rate and efficiency from inorganic semiconductor quantum dots to organic conjugated molecules are fundamental key problems to optimizing the performances of inorganic/organic hybrid solar cells. In our project, we will study the ultrafast charge separation dynamics at heterojunction interface between quantum dots and organic charge acceptors via femtosecond laser pump-probe spectroscopy; we will explore the most optimal condition of charge separation by changing the surface shell structures and organic ligands of CdSe quantum dots. Firstly, CdSe quantum dots with different sizes and shell structures will be synthesized, and then these quantum dots will be modified by the conductive short-chain organic molecules via surface ligand exchange. Secondly, we will investigate the effect of themal treatment of CdSe quantum dots/organic conjugated polymer bybrid film on surface morphology and charge separation. Thirdly, we will study the shell structures, the chain length of ligands and energy level alignment turnable charge separation dynamics from quantum dots to organic charge acceptors via the time resolved fluorescence and transient absorption spectroscopy. Finally, we will theoretically analyze the controlling mechanism of charge tranfer by the interfacial electronic coupling force. It is promising to significantly improve the power conversion efficiency of quantum dots based solar cells by understanding the basic physical mechanism in these devices.

提高半导体量子点到有机共轭分子的电荷分离速率和效率是优化无机/有机杂化太阳能电池效率的关键基础问题。本项目将利用飞秒激光泵浦-探测技术研究量子点与有机电荷受体之间的超快电荷分离动力学过程，改变纳米晶表面壳层结构和有机配体分子，探索界面快速电荷分离的最优化条件。我们将合成不同尺寸和壳层结构的CdSe量子点，通过表面配体交换将其修饰具有导电功能的短链有机配体分子；研究热处理对CdSe量子点/有机聚合物薄膜表面形貌和电荷分离速率的影响；利用时间分辨荧光和瞬态吸收光谱探测量子点与电荷受主之间的电荷转移速率，分析壳层结构、有机配体链长、能级取向等因素对电荷分离过程的影响；从理论上分析无机/有机界面电子耦合对电子转移速率的调控机理。上述基础物理问题的解决，将为改进量子点太阳能电池的光电转换效率提供物理学的基础。

基于半导体纳米晶与有机共轭分子的有机/无机复合材料有望应用于高效柔性的光伏器件，然而纳米晶与有机共轭分子之间的界面电荷过程还不清楚。本项目利用飞秒激光泵浦-探测技术研究了半导体纳米晶与有机电荷受体之间的超快电荷分离的动力学过程。我们合成了不同壳层结构的Mn2+离子掺杂纳米晶和CuInS2量子点，研究了他们的热稳定性，以及电子-空穴波函数在壳层中的分布状况；以亚甲基蓝分子为连接的桥梁，提高了CdSe量子点到氧化石墨烯的电荷分离及传输的效率；研究了CdSe四足棒纳米晶中载流子弛豫及复合的动力学过程，观察到电子从棒的能级弛豫到核中心的能级需要1ps，而核中心能级电子的寿命可达到5ns，并且高激发密度下有利于热电子从纳米晶中分离到有机电荷受体分子。认识理解纳米晶与有机共轭分子界面的超快电荷分离过程，对优化量子点光伏器件的光电转换效率具有重要的意义。

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