【作者】 宣荣卫；

【导师】 李岚； 张晓松； 徐建萍；

【作者基本信息】 天津理工大学 ， 光学， 2011， 硕士

【摘要】 胶体量子点具有发光光谱随粒径调控的特性,近年来逐渐在显示和照明器件领域得到应用。由于良好的单色性,CdSe量子点被广泛应用到新型显示器件中,但也因此限制了其在照明领域的应用。ZnS量子点具有丰富的缺陷结构,发射峰呈现为可调控的宽带光谱,且发光效率高,因此有利于实现色温可调控的、高亮度的白光发射并在照明领域取得应用。本文就ZnS量子点缺陷的光致发光（PL）和电致发光（EL）的调控规律展开研究:1)采用超重扩散法和化学沉淀法制备了不同超重环境、不同Zn/S比例、不同合成温度等几个系列的ZnS量子点材料,分析了PL光谱变化规律和作用机制。选取部分量子点材料利用旋涂成膜工艺制备了ZnS量子点薄膜和ZnS量子点-聚合物复合薄膜,利用扫描电子显微镜（SEM）和PL光谱等手段对薄膜的形貌和发光特性进行了讨论。2)制备了系列ITO/ZnS量子点/Al单层和多层EL器件。系统地研究电场激发下器件的发光特性,借助PL分析获得了器件的工作机理。对于电压改变下的器件峰值位置从黄绿光（560 nm）到蓝光（470 nm）的移动现象由选择性激发过程,即驱动电压对不同缺陷能级有选择性的激发过程决定;对于不同Zn/S比例下制备的量子点,PL光谱和EL光谱呈现相反的移动趋势,提出了“扩展缺陷带”的概念来解释这一现象,即缺陷带的扩展使浅缺陷能级间距离增加而深缺陷能级间距离减小,最终导致了两种光谱相反的移动趋势;我们同时讨论了尺度效应对ZnS量子点EL光谱的调控机理,认为除了量子尺寸效应,与缺陷能级相关的发射随着量子点尺寸的变化也是重要的原因之一,同时提出这种现象预示了一种调节器件色温的新方法;为了更有效地调节色温,我们还尝试添加了有机材料（分别为MEH-PPV和PVK:NPB）制备ZnS量子点-有机物复合器件,并获得了较好的色温调控效果。3)在不同浓度的SiO₂乙醇溶液中制备了一系列ZnO量子点/SiO₂复合材料,通过匀胶的方法制备出复合薄膜器件。SiO₂在器件中不但起到平衡载流子的作用,而且其对ZnO量子点的尺寸及缺陷的影响共同起到对EL光谱的调控作用。更多还原

【Abstract】 With size-tunable luminescent properties, colloidal quantum dots （QDs） have been applied in display and lighting devices. CdSe QDs were adopted in display devices, thanks to good monochromaticity, but not in lighting devices. ZnS QDs shows broadband emissions from the transitions between the abundant of intrinsic defects. Due to variable spectra and high luminescent efficiency, they are expected to realize high-efficiency white light emission with varying color temperature. In this dissertation, we focus on the natue of photoluminescence （PL） and electroluminescences （EL） from the defects of ZnS QDs. The main experiments and discussions are as follows:1) The new synthesis progress named Diffusion of Solvents in Overweight State, and chemical precipitation were co-adopted to prepare ZnS QDs. The series of QDs were obtained by changing the preparation conditions of overweight state, Zn/S molar ratios and temperature. The nature and mechanism of PL from the QDs are discussed. QDs and QDs-polymer composite films were fabricated by spin-coating technology and characterized by SEM images and PL spectra.2) Series of ITO/ZnS QDs/Al single-layer and multilayer EL devices were fabricated. Behaviors of the EL devices were studied systematically and their working mechanisms were discussed with the help of PL analysis. EL emission peak were tuned from yellow-blue （560 nm） to blue （470 nm） with the increasing voltage, which determined by selective excitation processes （SEPs）. And extended-defect-bands were proposed to explain the contrary shift between PL and EL spectrum for different Zn/S ratios, in which shallow and deep defect levels were selected to be excited by PL and EL. Particle size-dependent wideband EL of ZnS QDs suggested a possibility of adjustment of color temperature for lighting devices. Its origin may be not only related to quantum size effect but also the emission proportion from different defects. Further detailed discussion on regulating color temperature by means of QDs-polymer composite film showed that ZnS QDs/MEH-PPV and QDs/ PVK:NPB composite film device were beneficial to achieve good performance.3) Another composite film device was fabricated with ZnO QDs/SiO₂ composite which were synthesized in different concentration of SiO₂-ethanol solution. SiO₂ not only balanced the carriers of device but controlled the size and the defects of ZnO QDs which co-operated to shift the EL spectra.更多还原