本文關(guān)鍵詞： 量子點 薄膜 跳躍輸運 陷阱效應 界面電荷轉(zhuǎn)移　出處：《哈爾濱工業(yè)大學》2017年碩士論文　論文類型：學位論文

【摘要】：半導體量子點材料由于其獨特的量子限域效應和光電特性,目前已被人們廣泛應用于能源材料、發(fā)光器件等方面。人們研究量子點薄膜中載流子的輸運特性,為量子點薄膜光電器件的結(jié)構(gòu)設(shè)計與性能改進提供了理論依據(jù)。目前,在量子點薄膜的載流子輸運方面,關(guān)于載流子在薄膜中時空分布情況的理論研究報道并不多見。TOF實驗上只能檢測載流子輸運帶來的全局光電流信號,不易具體分析不同傳輸層中載流子輸運過程和界面電荷轉(zhuǎn)移過程。本文以CdSe量子點薄膜的光生載流子為主要研究對象,以半導體連續(xù)性方程、電流方程和跳躍速率方程為主要理論研究基礎(chǔ),研究了在量子點薄膜中載流子的輸運過程,主要包含以下幾部分研究內(nèi)容:首先,基于跳躍模型,利用COMSOL有限元軟件中的PDE模塊建立三個可以相互耦合的物理場。第一個物理場是針對載流子的擴散運動與漂移運動,用于研究量子點薄膜的載流子輸運過程及其對全局電流的貢獻。第二個物理場是針對載流子被陷阱俘獲與釋放過程,用于研究存在陷阱效應的載流子輸運過程。第三個物理場是針對平面異質(zhì)結(jié)處的界面電荷轉(zhuǎn)移對載流子輸運的影響,用于研究不同尺寸雙層量子點薄膜的載流子輸運過程。其次,根據(jù)實際量子點薄膜的材料特性進行仿真計算,研究了量子點薄膜中的載流子跳躍輸運過程。不考慮陷阱效應時,載流子的擴散運動增加了TOF信號的持續(xù)時間,漂移運動影響TOF信號峰值。存在陷阱效應時,仿真TOF信號與實驗信號比較相符,說明實際載流子輸運過程中存在陷阱俘獲/釋放電荷的過程,陷阱的存在導致載流子擴散運動的不對稱性,增加了TOF信號的持續(xù)時間。最后,仿真研究了平面異質(zhì)結(jié)處的界面電荷轉(zhuǎn)移過程。界面兩側(cè)的能級匹配結(jié)構(gòu)決定了界面電荷轉(zhuǎn)移的速率,界面電荷轉(zhuǎn)移的速率影響TOF信號峰值。同時,界面電荷轉(zhuǎn)移的速率與外加電場的強度大小有關(guān)。
[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.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O471.1;O484
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本文編號：1519119