基于量子点的LED性能测试与分析研究

论文总字数：31909字

摘 要

量子点(Quantum dots，简称QDs)由于性能稳定、尺寸可控、分散性好、光色可调、发光强度大、色纯度高、荧光寿命长、单光源可激发多色荧光等优势，使得它在光电子器件和生物标记等领域有着广泛的应用前景。量子点能够产生多种量子效应，如量子尺寸效应、量子限域效应、量子表面效应、介电限域效应、宏观量子隧道效应等，使其展现出出色的物理性质，衍生出了不同于常规材料体系的许多特性，尤其表现在电学和光学上，并且在非线性光学、催化、磁介质、医药及光电等功能材料领域具有极为广阔的应用前景。

本论文主要研究量子点的光学特性及其电学特性，以CdSe量子点材料为载体展开对量子点材料的光电性能探究。通过对不同条件下荧光谱线的测量得到发光峰变宽超过11%，峰位红移超过26mev（远大于CdSe量子点中激子结合能15meV），且吸收强度减弱约14.5%。量子点电致发光研究中发现了明显的量子限制Stark效应。量子点在电场作用下，电子和空穴都被拉向两侧，电子和空穴之间是存在相互作用的，电场作用力是轻微的使电子和空穴的分离减弱，致使整体的电子-空穴对的净能量减少，所以量子点的吸收峰红移。Stark位移随量子点尺寸的增加而增加，随场强增加stark位移呈非线性增加，且随尺寸增加量子点极化率增加。

实验结果显示随温度升高荧光光谱峰位红移，绿光量子发光器件的光谱峰位由528nm红移到534nm。这是因为温度升高，半导体材料内能增加．原子振动幅度增大，从而使得原子间距增大，原子间距增大导致材料中电子的平均势能降低，材料带隙宽度的减小，因而荧光峰红移。随电压增大，荧光峰发生明显的红移且强度减弱，这同样是由于电场作用下禁带宽度变窄，荧光峰红移。

相对于吸收谱，荧光峰的红移较小，这是由于II—VI族半导体量子点复杂的能带结构造成的，第一个吸收峰对应的光学跃迁与荧光峰对应的跃迁不同，因此吸收峰和PL峰对应的斯塔克位移也不同。而吸收峰和发射峰其极化性质均相同，在外电场作用下，电子空穴间距离增大，电子振动强度减弱，吸收峰峰和荧光峰的强度减弱，半高宽均变宽。

关键词： 量子点，红移，电致发光，光致发光，量子限制Stark效应

Abstract

Quantum dots, called QDs. Because of stable,controllable size, dispersion, light color adjustable light intensity, high color purity, long fluorescence lifetime, a single light source can be multicolor fluorescence excitation and other advantages, make it In the field of optoelectronic devices and biomarkers it has a wide range of applications. Quantum dots can produce a variety of quantum effects, such as quantum size effect, quantum confinement effect, quantum surface effects, the dielectric confinement effect, macroscopic quantum tunneling effect, etc., to show the excellent physical properties, derived from a different from the conventional Many characteristics of the material system, especially in the electrical and optical on and have a very broad application prospects in the functional areas of nonlinear optics, catalysis, magnetic media, medical and optical and other materials.

In this thesis, the optical properties and electrical properties of quantum dots to CdSe quantum dot materials for the carrier to expand on photoelectric properties of quantum dot material to explore. Under different conditions by measuring the fluorescence spectrum emission peak broadening obtain more than 11%, peak red-shift more than 26mev (much larger than the CdSe quantum dot exciton binding energy 15meV), and the absorption intensity decreased about 14.5%. Quantum dot electroluminescent study found significant quantum confinement Stark effect. Quantum dots in the electric field, the electrons and holes are pulled to between the two sides, the interaction between electrons and holes are present, the field force is a slight separation of electrons and holes weaken, resulting in overall e - hole pairs reduce net energy, so absorption red-shift quantum dots. Stark shift with increasing quantum dot size increases, strong stark increases nonlinearly with increasing displacement field, and with the increased size of the quantum dot polarization rate increases.

The results showed that with increasing temperature, green light-emitting device fluorescence spectrum peaks is moved from 528nm to 534nm. This is because the temperature increases, the semiconductor material’s internal energy increased. Atomic vibration amplitude increases, so that the interatomic distance increases, the atomic spacing increases resulting in the average potential energy of electrons in the material decreases, reducing the width of the band gap material, so fluorescence peak red-shift. With voltage increases, the fluorescence peaks obvious red shift and strength diminished, which is also due to the band gap of the electric field is narrowed, the fluorescence peak red-shift.

Analysis the absorption spectrum, fluorescence peak red-shift small, this is due to II-VI semiconductor quantum dots complex band structure caused, the first optical transitions with fluorescence peaks different the absorption transition peak , and therefore the absorption PL peaks corresponding to the peaks and Stark shift is different. The peak absorption and emission polarization properties are the same, external electric field between the electron-hole distance increases, electronic vibration intensity decreased absorption peak and peak fluorescence intensity decreased FWHM were widened.

Key words:Quantum dot;Red-shift;Electroluminescent;Photoluminescence;Quantum confinement Stark Effect

目录

摘要 I

Abstract II

第一章 绪论 1

1.1引言 1

1.2 量子点的概述 2

1.3量子点的基本特性 2

1.3.1量子尺寸效应 2

1.3.2表面效应 2

1.3.3宏观量子隧道效应 2

1.3.4介电限域效应 3

1.4 量子点器件发光原理 3

1.5 量子点光电特性 4

1.6 量子点的制备方法 5

1.6.1金属有机合成法 5

1.6.2水相合成法 5

1.7量子点LED的前景与挑战 6

1.8本论文研究内容 6

第二章 量子点的电致发光机理研究 7

2.1引言 7

2.2电致发光器件基本原理 8

2.3量子点器件电致发光原理 8

2.4量子点在WLED中的优势 9

2.5量子点光致发光红移可能性 9

2.6量子点的寿命 9

第三章 基于蓝光LED的量子点的性能測试 11

3.1引言 11

3.2 实验设备介绍 11

3.3实验内容 13

3.3.1实验准备 13

3.3.2性能测试 13

3.3.3寿命试验 14

3.4实验结果 15

3.4.1不同尺寸CdSe量子点溶液的光致荧光光谱 15

3.4.2不同量子点尺寸的LED的光致发光光谱 16

3.4.3发光光谱归一化对比 16

3.4.4不同量子点尺寸的LED的激发谱和吸收谱 17

3.4.5 GaN蓝光LED的电流与电压关系 18

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