SUFFICIENT DIMENSION REDUCTION AND VARIABLE SELECTION VIA INDEPENDENCE MEASURES

基于一些独立性准则的充分降维和变量选择

伍润雄

11930643

硕士

数学

CHEN XIN

2021-05-15

2021-06-15

南方科技大学

深圳

Colloidal quantum dots can be used as an emitting source for displays because they have an emission wavelength that is adjustable according to the size of the quantum dots and the light-emitting region covers the visible light region.Microcavity structure quantum dot light-emitting diodes (QLEDs) devices, due to the microcavity effect, have a higher light-emitting efficiency and a narrower electroluminescent (EL) spectrum than the traditional bottom-emitting devices. QLEDs based on InP do not contain cadmium, which will not harm the human body and the environment. The relatively low light-emitting efficiency (1.2%), and the wide full width at half-maximum (FWHM) (48 nm) of the EL spectrum of QLEDs based on InP can just be improved by using the microcavity structure.In this dissertation, the QLEDs based on CdSe with Ag anode and Ag cathode microcavity structure were prepared firstly, and the performance of the microcavity structure QLEDs was compared with that of the traditional bottom-emitting device with ITO as the bottom electrode. By optimizing the cavity length, the device's luminous efficiency is more than twice that of the bottom-emitting device, and the FWHM of the EL spectrum is reduced from 36 nm to 28 nm.Next, two structures of InP-based QLEDs are prepared. One is an inverted bottom emission standard device with ITO as the bottom electrode. The other is a microcavity device with silver or aluminum as the bottom electrode, and the thin layer of silver as a semitransparent top electrode. The conventional QLEDs based on InP have lower luminous efficiency, lower current density, and larger turn-on voltage, and the FWHM of the EL spectrum is up to 48 nm, which is larger than the FWHM of the EL spectrum of conventional CdSe-based QLEDs. In order to improve the performance of InP-based QLEDs devices, we fabricated QLEDs with microcavity structure. We optimized the cavity length, top electrode thickness of the microcavity device and studied the influence of capping layer on the performance of the microcavity device. By researching InP-based microcavity devices, InP-based QLEDs with low turn-on voltage and narrow (18 nm) emission spectrum were fabricated, which solved the problem that InP-based conventional QLEDs have a much broader EL spectrum than Cd-based conventional QLEDs.

胶体半导体量子点具有发光波长可调，发光色纯度高，发光波段覆盖可见光区域的优点，在显示和照明领域有广泛的应用。所谓光学微腔，是指在一维或多维方向上尺寸与光波波长相当的微型光学谐振器。微腔结构的量子点发光二极管（quantum dot light-emitting diodes, QLEDs）器件，由于微腔效应，其发光效率相比传统的以ITO 作底电极的底发射器件提高了，电致发光（electroluminescence, EL）光谱的半高宽也相较于非微腔结构底发射器件更窄。基于磷化铟（InP）的QLEDs 器件，其量子点不含镉，不会对人体和环境产生危害，是未来环境友好型显示器件的发展方向。但是基于InP 的QLEDs器件的发光效率相对较低（1.2%），开启电压大（5.4V），发光光谱的半高宽也较宽（full width at half maximum, FWHM）（48 nm），这些问题正好可以利用微腔来改善。本论文首先制备了基于硒化镉（CdSe）的用银作正极和负极的微腔结构的QLEDs 器件，对比分析了微腔结构QLEDs 器件的性能与传统的以ITO 作底电极的底发射器件的性能差异。通过优化腔长，微腔结构的器件的发光效率是底发射器件效率的两倍多，而且发光光谱半高宽从36 nm 减小到了28 nm。本论文接着制备了两种结构的基于InP 的QLEDs 器件，其中一种是以ITO 作底电极的倒置底发射标准器件，另一种是以全反射的银或者铝作为底电极，部分反射的银作为顶电极的微腔器件。基于InP 的QLEDs 标准器件其发光效率较低，电流密度较小，开启电压较大，而且EL 光谱的半高宽达到了48 nm，比基于CdSe的QLEDs 标准器件的EL 谱的半高宽大了12 nm。为了改善InP 标准器件的性能，我们制备了微腔结构的QLEDs 器件，优化了器件的腔长、顶部电极厚度并研究了折射率匹配层对微腔器件性能的影响。最终，我们制备出了开启电压低，EL 光谱半高宽窄（18 nm）的基于InP 的QLEDs 微腔器件，解决了基于InP 的QLEDs 标准器件EL 光谱半高宽（48 nm）比基于CdSe 的QLEDs 标准器件（36 nm）宽的问题。

quantum-dot light-emitting diodes microcavity CdSe InP

量子点发光二极管 微腔 硒化镉 磷化铟

英语

独立培养

南方科技大学

Wu RX. SUFFICIENT DIMENSION REDUCTION AND VARIABLE SELECTION VIA INDEPENDENCE MEASURES[D]. 深圳. 南方科技大学,2021.