CdSe量子点薄膜中光生载流子输运特性的仿真研究

发布时间：2018-02-20 07:42

  本文关键词： 量子点 薄膜 跳跃输运 陷阱效应 界面电荷转移　出处：《哈尔滨工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：半导体量子点材料由于其独特的量子限域效应和光电特性,目前已被人们广泛应用于能源材料、发光器件等方面。人们研究量子点薄膜中载流子的输运特性,为量子点薄膜光电器件的结构设计与性能改进提供了理论依据。目前,在量子点薄膜的载流子输运方面,关于载流子在薄膜中时空分布情况的理论研究报道并不多见。TOF实验上只能检测载流子输运带来的全局光电流信号,不易具体分析不同传输层中载流子输运过程和界面电荷转移过程。本文以CdSe量子点薄膜的光生载流子为主要研究对象,以半导体连续性方程、电流方程和跳跃速率方程为主要理论研究基础,研究了在量子点薄膜中载流子的输运过程,主要包含以下几部分研究内容:首先,基于跳跃模型,利用COMSOL有限元软件中的PDE模块建立三个可以相互耦合的物理场。第一个物理场是针对载流子的扩散运动与漂移运动,用于研究量子点薄膜的载流子输运过程及其对全局电流的贡献。第二个物理场是针对载流子被陷阱俘获与释放过程,用于研究存在陷阱效应的载流子输运过程。第三个物理场是针对平面异质结处的界面电荷转移对载流子输运的影响,用于研究不同尺寸双层量子点薄膜的载流子输运过程。其次,根据实际量子点薄膜的材料特性进行仿真计算,研究了量子点薄膜中的载流子跳跃输运过程。不考虑陷阱效应时,载流子的扩散运动增加了TOF信号的持续时间,漂移运动影响TOF信号峰值。存在陷阱效应时,仿真TOF信号与实验信号比较相符,说明实际载流子输运过程中存在陷阱俘获/释放电荷的过程,陷阱的存在导致载流子扩散运动的不对称性,增加了TOF信号的持续时间。最后,仿真研究了平面异质结处的界面电荷转移过程。界面两侧的能级匹配结构决定了界面电荷转移的速率,界面电荷转移的速率影响TOF信号峰值。同时,界面电荷转移的速率与外加电场的强度大小有关。
[Abstract]:Semiconductor quantum dots (QDs) have been widely used in energy materials, luminescent devices and other fields due to their unique quantum limiting effect and optoelectronic properties. It provides a theoretical basis for the structure design and performance improvement of quantum dot thin film optoelectronic devices. At present, in the field of carrier transport of quantum dot thin film, There are few reports on the spatiotemporal distribution of carriers in thin films. TOF can only detect the global photocurrent signals from carrier transport in experiments. It is not easy to analyze the carrier transport process and the interfacial charge transfer process in different transport layers. In this paper, the photogenerated carriers of CdSe quantum dot films are taken as the main research object, and the semiconductor continuity equation is taken as the main research object. Based on the current equation and jump rate equation, the transport process of carriers in quantum dot films is studied. The main contents are as follows: firstly, based on the hopping model, By using the PDE module of COMSOL finite element software, three physical fields can be coupled with each other. The first one is aimed at the diffusion and drift motion of carriers. In order to study the carrier transport process and its contribution to the global current in quantum dot thin films, the second physical field is aimed at the trapping and releasing process of carriers. The third physical field is aimed at the effect of the interface charge transfer at the plane heterojunction on the carrier transport. It is used to study the carrier transport process of double layer quantum dot thin films with different sizes. Secondly, according to the material characteristics of the actual quantum dot films, the carrier hopping transport process in quantum dot films is studied. When the trap effect is not considered, The diffusion motion of carrier increases the duration of TOF signal, and the drift motion affects the peak value of TOF signal. In the presence of trap effect, the simulated TOF signal is in good agreement with the experimental signal. It is shown that there is a trapping / releasing process in the actual carrier transport process, and the existence of the trap leads to the asymmetry of carrier diffusion motion, which increases the duration of the TOF signal. The interface charge transfer process at the plane heterojunction is simulated. The energy level matching structure on both sides of the interface determines the interface charge transfer rate, and the interface charge transfer rate affects the peak value of the TOF signal. The rate of charge transfer at the interface depends on the intensity of the applied electric field.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O471.1;O484
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本文编号：1519119