基于8-羟基喹啉及其衍生物的有机小分子电致发光材料

第25卷第7期2013年7月

化　学　进　展

PROGRESS IN CHEMISTRY

Vol.25No.7　Jul.,2013

收稿:2012年11月,收修改稿:2013年3月

　∗国家自然科学基金项目(No.60978059,60205040)、教育部新世纪优秀人才支持计划(NCET⁃10⁃0176)、四平市科技局项目(No.2011015)和吉林省创新团队项目(No.20130521019JH)资助

∗∗Corresponding author　e⁃mail:liuchunbo47@;guangboche@

基于8⁃羟基喹啉及其衍生物的有机小分子

电致发光材料

∗

苏　斌1　赵　静1　刘春波2∗∗　车广波1∗∗　王庆伟2　徐占林2

(1.吉林师范大学环境科学与工程学院　四平136000;

2.吉林师范大学化学学院　四平136000)

摘　要　有机电致发光器件因驱动电压低、亮度和效率高等优点,已经成为最具潜力的平板显示技术。自以8⁃羟基喹啉铝为发光材料制备双层有机电致发光器件开始,科研人员在发光材料设计合成方面做了大量工作并取得了重大研究进展。在小分子荧光材料中,8⁃羟基喹啉及其衍生物为配体的有机金属配合物因合成方法简单、发光效率和亮度高、成膜性好等优点而被广泛应用。本文简述了有机电致发光器件的优点、结构及工作原理,重点介绍了基于8⁃羟基喹啉及其衍生物为配体的有机小分子电致发光材料的研究现状。从分子设计的角度出发,旨在总结8⁃羟基喹啉及其衍生物为配体的有机小分子电致发光材料对有机电致发光器件性能的影响,包括:以8⁃羟基喹啉为单一配体的有机金属配合物展示了良好的电子传输能力、亮度高且可作为基质材料等卓越的特性;通过对8⁃羟基喹啉的苯氧环或吡啶环进行修饰可以调节电致发光颜色;混合配体的使用可以增加玻璃化温度、改善薄膜形貌进而提高器件的效率和稳定性。最后,对该领域存在的问题和有机电致发光材料的应用前景作了评述。

关键词　8⁃羟基喹啉　衍生物　混合配体　有机电致发光器件　电致发光

中图分类号:O644.1;O626.32　文献标识码:A　文章编号:1005⁃281X(2013)07⁃1090⁃12

Small Molecular Organic Electroluminescent Materials Based on

8⁃Hydroxyquinoline and Its Derivatives

Su Bin 1　Zhao Jing 1　Liu Chunbo 2∗∗　Che Guangbo 1∗∗　Wang Qingwei 2　Xu Zhanlin 2

(1.College of Environmental Science and Engineering,Jilin Normal University,Siping 136000,China;

2.College of Chemistry,Jilin Normal University,Siping 136000,China)

Abstract Organic light⁃emitting diodes (OLEDs)have emerged as a potential candidate for new flat panel

display due to their advantages such as low driving voltage,high brightness and luminous efficiency.Since tris(8⁃hydroxyquinolinato)aluminum (Alq 3)⁃based double layer thin⁃film device was prepared,much progress has been

made in new electroluminescence (EL)materials which were designed and synthesized by anic metal complexes based on 8⁃hydroxyquinoline and its derivatives are widely used due to simple synthesis,high luminance and efficiency as well as superior film morphology.This paper sketches the advantages,construction and working mechanism of OLEDs and stresses the research progress in small molecular organic EL materials based on

8⁃hydroxyquinoline and its derivatives as ligands.This article is written basically from the molecular design point of

view and aims at the significant developments in metal organic complexes based on 8⁃hydroxyquinoline and its

第7期苏　斌等　基于8⁃羟基喹啉及其衍生物的有机小分子电致发光材料·1091

　·derivatives that have been designed and synthesized intentionally for OLEDs.Firstly,organic metal complexes based on8⁃hydroxyquinoline as single ligand show favourable characteristics such as excellent electron⁃transport capability,high brightness and employment as host materials.Secondly,the EL colors could be tuned by modification of substituents at phenoxide or pyridine ring.Thirdly,the usage of mixed ligand can increase glass transition temperature and decorate morphology of film then result in high efficiency and stability.In the end,the current status,existing issues and prospects in this field are also discussed.

Key words　8⁃hydroxyquinoline;derivatives;mixed⁃ligands;organic light⁃emitting diodes; electroluminescence

Contents

1　Introduction

2　Structure and working mechanism of OLEDs 2.1　Structure of OLEDs

2.2　Working mechanism of OLEDs

3　Application of8⁃hydroxyquinoline organic metal complexes in OLED

3.1　8⁃Hydroxyquinoline as single ligand

3.2　Derivatives of8⁃hydroxyquinoline as ligands 3.3　Complexes of mixed⁃ligands

4　Conclusion and outlook

1　引言

有机电致发光器件(organic light⁃emitting diodes,OLEDs)由于驱动电压低、反应时间短、发光亮度和效率高以及易于调制颜色实现全色显示等优点,已成为21世纪电致发光(electroluminescence, EL)领域最具潜力的平板显示技术。早在20世纪60年代,科研人员就开展了对有机EL现象的相关研究,但是由于早期器件的性能如启亮电压、亮度和效率等均不理想,因此未能引起广泛的研究兴趣[1,2]。直到1987年,Kodak公司的Tang等采用芳香二胺(TPD)作为空穴传输层,8⁃羟基喹啉铝(A1q3)作为发光层兼电子传输层,功函数低且稳定的Mg:Ag合金作为电极,研制出了驱动电压约为10V、亮度>1000cd/m2、流明效率为1.5lm/W的超薄膜OLEDs[3]。这一结果极大地激发了人们对有机EL的研究热情,使OLEDs的研究进入了一个划时代的迅速发展阶段[4—8]。

在小分子荧光材料中,以8⁃羟基喹啉(q)及其衍生物为配体的有机金属配合物由于其卓越的性能如电子传输能力高、膜形态稳定、合成方法简单等而被广泛应用。本文从配体出发,讨论不同配体对配合物性质及OLEDs性能的影响,分析此类配合物应用于OLEDs的优点和局限性,并展望其在OLEDs 中的应用前景。

2　OLEDs的结构和EL机理

2.1　OLEDs的结构

OLEDs多采用夹层式三明治结构,典型的三层OLEDs结构示于图1(a)。为了优化器件的性能,在器件结构中引入的各种功能层,可以明显改善OLEDs的性能,如图1(b)。例如,电子注入层和空穴注入层往往能降低器件的启亮或工作电压;电子阻挡层和空穴阻挡层往往能减小直接流过器件而不形成激子的电流,从而提高器件的效率

。

图1　典型的有机电致发光器件结构示意图

Fig.1　The typical structures of organic light⁃emitting diodes(ITO:indium⁃tin oxide;HIL:hole inject layer;HTL: hole transport layer;EBL:electron block layer;EML:emitting material layer;HBL:hole block layer;ETL:electron transport layer;EIL:electron inject layer)

2.2　OLEDs的EL机理

OLEDs的发光属于注入型发光,在正向电压驱动下,阳极向发光层注入空穴,阴极向发光层注入电子。注入的空穴和电子在发光层中相遇结合成激子,激子复合并将能量传递给发光材料,后者经过辐射弛豫过程而发光。其发光过程可分为以下5个阶段,如图2所示:

(1)电子和空穴分别从阴极和阳极注入;