铯铅卤钙钛矿量子点的合成及其光谱转换型LED应用研究

发布时间：2018-03-30 02:34

本文选题：钙钛矿　切入点：CsPbX_3　出处：《合肥工业大学》2017年硕士论文

【摘要】：量子点是指由少量原子组成,电子运动在各个方向上均受到限制的纳米颗粒。量子点最显著的特征是具有量子限域效应,其带隙随尺寸的改变会发生显著的变化。此外,量子点还具有尺寸效应、表面效应、隧穿效应等特性,这使它们在光电器件领域扮演着重要的角色。铯铅卤(CsPbX_3)钙钛矿量子点具有诸多优异的性能,表现出较为出色的量子效应,体现在量子产率高、单分散性好、发射谱半峰窄、荧光随成份可调、稳定性高、合成工艺简便等方面,这使CsPbX_3量子点在包括LED、光电探测器、量子点激光器、太阳能电池等功能器件上具有极高的应用价值。本文从CsPbX_3钙钛矿量子点的合成工艺入手,对其合成工艺进行了改进,对反应过程、量子点的性质作了相关的研究,并实现了CsPbX_3量子点在下转换单色光及白光LED器件上的应用,主要取得了以下研究成果:(1)以硬脂酸、十八烯胺为配体,在十八烯环境下合成了高质量单分散的CsPbBr_3量子点,表征结果显示该量子点表现出明显的激子吸收特征,在紫外-可见区域有较高的吸收率,具有尖锐的发射谱,半峰宽低至21nm,荧光量子产率高至86%;该量子点为立方相结构,具有良好的结晶性,正方形的纳米晶具有良好的单分散性,具有与其激子波尔半径(7nm)相当的平均尺寸(10.2nm);实验结果表明,该反应具有极快的反应速率,在反应3秒即可完成大部分反应,反应时间对产物的光谱有一定的影响,随反应时间延长,量子点的尺寸分布逐渐集中;利用硬脂酸作配体可以有效降低所需反应温度,体系在80℃-160℃均具有优良的结晶产物,在120℃时有最高的荧光强度。(2)采用锌的卤化盐对母体CsPbBr_3量子点进行阴离子交换,获得了高质量的交换产物量子点。该反应可以在常温下进行,不需要惰性气体保护;反应速率快,数秒钟即可结束反应;通过调节卤盐添加量,产物的发射光谱可以覆盖410-700nm整个可见光波段,可以轻易获得直接合成法难以合成的CsPbCl3量子点;对于常温下通常呈正交相的CsPbI3量子点,可以轻易地在常温下获得具有高荧光的立方相CsPbI_3量子点,并且该产物在大气环境下具有较高的稳定性。通过对反应过程进行追踪,发现调节体系中各种阴离子的比例,可以有效调节发射光谱的位置,该反应为可逆反应,量子点晶体与外界存在快速的交互关系;反应可分两段进行,包括快速的晶体表面反应与相对慢速的晶体内部离子交换。交换产物具有较高的稳定性,主要继承了母体CsPbBr_3量子点的稳定性,并且反应中未丢失表面配体。对量子点从短波到长波发射谱半峰宽变大的原因提出了假设,由于量子点尺寸与其激子波尔半径相对大小不同,量子点尺寸波动对带隙宽度的变化影响不同:在短波段影响小,故半峰较窄;在长波段影响大,故半峰较宽。(3)利用阴离子交换产物量子点作为下转换层,构建了单色光LED和白光LED。单色光LED具有较高的单色性,发射光谱半峰可低至18nm,其色纯度可高达99%以上;具有相对较高的流明效率,绿光LED的流明效率达21.5lmW-1;在不同的驱动电流下,其发射光具有极高的稳定性。对于白光LED,利用阴离子交换获得的红光量子点可以通过增加红色光成份显著提高白光LED的显色指数(90.5%),降低其相关色温(3561K),对驱动电流具有较高的稳定性,提高了荧光粉的实际使用价值。
[Abstract]:Quantum dots are composed of a small number of atoms, electrons are confined nanoparticle quantum dots in all directions. The most significant feature is a quantum confinement effect, the band gap size will change dramatically. In addition, quantum dot has size effect, surface effect, tunneling effect other characteristics, which makes them play an important role in the field of photoelectric devices. Lead halide cesium (CsPbX_3) perovskite QDs has many excellent properties, exhibit more excellent quantum effects, reflected in the high quantum yield, good monodispersity, narrow half peak emission spectrum, fluorescence with adjustable composition, high stability the synthesis process is simple, etc., which makes CsPbX_3 quantum dots in LED, photoelectric detector, quantum dot lasers, has a very high value of solar cell devices. The synthesis of CsPbX_3 quantum dots with perovskite, The synthesis process was improved, the reaction process, properties of quantum dots were researched, and the realization of the application of CsPbX_3 quantum dots in conversion of monochromatic light and white light LED devices, the main research results are as follows: (1) with stearic acid, eighteen enamine ligand, CsPbBr_3 monodisperse quantum dots in the synthesis of high quality graphene eighteen environment characterization results show that the quantum dots exhibit distinct excitonic absorption characteristics in the ultraviolet visible region absorption rate is high, with sharp emission spectrum, half peak width as low as 21nm, the fluorescence quantum yield of up to 86%; the quantum dot the cubic phase structure, with good crystallinity, nanocrystalline square with good monodispersity, with its exciton Bohr radius (7Nm) average size (10.2nm); the experimental results show that the reaction rate of the reaction is very fast, in 3 seconds to complete the reaction Part of the reaction, has certain effect of spectral response time on the product, with the prolonging of reaction time, the size distribution of quantum dots are gradually concentrated; using stearic acid as ligands can effectively reduce the required reaction temperature. The system has excellent crystallization were at 80 DEG -160 DEG, have the highest fluorescence intensity at 120 DEG C (. 2) using zinc halide salt anion on the mother of CsPbBr_3 quantum dots exchange, quantum dots obtained exchange products of high quality. The reaction can be carried out at room temperature, without the protection of inert gas; fast reaction rate, the number of seconds to the end of the reaction; by adjusting the amount of salt brine, emission spectrum of the product can cover 410-700nm the whole visible light, can easily obtain the direct synthesis method is difficult to synthesize CsPbCl3 quantum dots; for room temperature is usually CsPbI3 quantum dots are orthogonal, can be easily obtained with high fluorescence at room temperature The cubic phase of CsPbI_3 quantum dots, and the product has high stability under atmospheric environment. Through tracking the reaction process that regulates a variety of anion system in proportion, can effectively adjust the position of the emission spectrum, the reaction is reversible, there is an interaction between the body and the external quantum dyking rapid reaction can be divided into two; some, including the crystal surface rapid reaction and relatively slow crystal internal ion exchange. The product has high stability, mainly inherited stability matrix of CsPbBr_3 quantum dots, and the reaction is not lost. Put forward the hypothesis of surface ligands cause quantum dots from shortwave to long wave emission spectrum FWHM becomes larger, because the size of quantum dots and Bohr exciton radius relative to the size of quantum dots of different sizes, change the width of band gap fluctuation on the influence in the short wavelength is small, so the half peak is narrow; In the long wave effect, the half peak is wide. (3) using anion exchange product of quantum dots as conversion layer, construct the monochromatic monochromatic light LED and white light LED. monochromatic light LED has high emission spectrum, the half peak can be reduced to 18NM, its color purity can reach more than 99%; with the high luminous efficiency, luminous efficiency of 21.5lmW-1 green LED; in different driving current, the emitted light has a very high stability. For white LED, the anion can exchange red quantum dots obtained by adding red light component significantly improve the color index of white LED (90.5%), reduce the correlated color temperature (3561K), the stability of the drive current is high, improve the phosphor applied value.

【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ422;TB383.1

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