强耦合体系界面超快电子转移的直接观测与调控的研究

The design and preparation of optoelectronic devices that can efficiently utilize light energy have always been the focus and hot spot of people's research. For the application of optoelectronic devices, how to improve the efficiency of photoelectric conversion has always been a key problem for scientists. How to transform the absorbed light into carriers as much as possible and then make the carriers separated followed by transported out, this process is the key to improve photoelectric conversion efficiency. In photoelectric devices, a large part of excited state electrons of the electron donor is decayed to the lowest state of excited state that can not be utilized, this physical process greatly limits the improvement of photoelectric conversion efficiency. In this project, we will focus on the research of the design and preparation of high efficiency optoelectronic devices, strong coupling enhanced and modulated interfacial ultrafast electron transfer: 1) exploring the design and preparation processes of structural cell of optoelectronic devices based on strong coupling; 2) Through femtosecond pump-probe technique to directly observe the electron transfer process, and studying the influence and mechanism of the strong coupling on the interfacial electron transfer process; 3) exploring the dependence of the interfacial electron transfer process on strong coupling, and establishing the corresponding quantitative relationship between them. All these researches not only reveal the inherent relationship between strong coupling and interfacial electron transfer, but also provide a new idea for improving photoelectric conversion efficiency, thus promoting the practical application of optoelectronic devices.

设计和制备能高效利用光能的光电器件一直是人们研究的重点和热点。对于光电器件的应用来说，如何提高光电转换效率始终是困扰科学家的关键难题。而如何尽可能多地把所吸收的光转换成载流子并分离输运出去则是提高光电转换效率的关键。光电器件中的电子供体有一大部分的激发态电子是驰豫到了激发态最低能态而不能被利用，这极大地限制了光电转换效率的提升。本项目拟围绕高效率光电器件的设计和制备、强耦合作用增强和调控界面处超快电子转移的实现展开如下研究：1）探索基于强耦合作用的光电器件结构单元的设计和制备工艺；2）利用飞秒泵浦探测技术直接观测电子转移过程，研究强耦合作用对界面电子转移过程的影响与作用机理；3）探究强耦合作用对界面电子转移过程的调控规律，并建立二者之间的定量对应关系。这些研究不但揭示了强耦合作用与界面电子转移之间的内在关联，也为光电转换效率的提升提供了一种新的思路，从而推动光电器件的实际应用。

基于单层二维材料的光电器件光电转换效率的提高是推动其实用化的关键。金属纳米结构或染料分子常被用于增强单层二维材料的光捕获和界面电荷转移，然而系统辐射损耗会弱化对所捕获光能的利用，不利于光电转换效率的提高。本课题通过结构设计和理论模拟构建强耦合结构并对其基本结构特征和光学特性进行了实验表征，利用飞秒时间分辨光学测量技术来直接观察和追踪异质结界面的电荷转移过程，建立起强耦合作用与界面电荷转移之间的对应关系。首先，我们自主搭建了多套光学测试系统，包括显微泵浦探测光学系统、显微集成光学系统（透反射谱、PL及SHG扫描成像、暗场散射谱）、显微角分辨谱、非线性光学测试系统（Z-Scan、OKE）等，为强耦合结构光学特性的表征提供了保障。然后，利用显微泵浦探测光学系统对二维材料本身的载流子动力学过程进行了观测，并定量表征了其表面缺陷和激子寿命，同时开展了等离激元效应增强超薄金纳米盘的光学非线性特性的研究，这些研究为该项目的顺利进行夯实了基础。紧接着我们设计了强耦合杂化结构，通过FDTD理论模拟得到最优结构参数，并利用电子束刻蚀方法和滴膜自组装方法制备了金纳米阵列结构，利用自主搭建的光学测试系统对其基本光学特性进行了系统的研究，并将利用飞秒时间分辨技术研究表面晶格模式与染料激子模式之间的强耦合效应对界面电荷转移过程的影响，以明确转移速率、数量与耦合强度之间的关系。本课题的研究不仅能揭示影响低维材料及杂化结构界面电荷产生及转移过程的关键因素，也可为高性能二维材料光电器件的开发与改进提供新思路。

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