【作者】 吴有智；

【导师】 蒋雪茵；

【作者基本信息】 上海大学 ， 材料学， 2004， 博士

【摘要】 有机薄膜电致发光作为一个新兴的研究领域不断吸引着越来越多的人们，目前已成为平板显示领域的一个研究热点。信息技术的飞速发展，对信息显示技术提出越来越高的要求。色彩丰富、低耗能、绿色环保、轻便甚至可卷曲的显示屏成为人们追求的目标。有机薄膜电致发光由于其低压驱动、高效发光、色彩丰富、响应快、视野宽及易于实现超薄轻便等优点，正迎合了这一要求，它必将成为信息时代一种理想显示技术。但有机电致发光本身是一个涉及化学、材料学、物理和电子等多学科的研究领域，这需要人们从材料的设计和合成、器件的制备、性能测试、发光过程和机理等多方面去研究。 本文主要侧重于研究器件结构、特性及发光机理等方面。首先，对蓝色有机电致发光器件进行了研究，获得了高效率色纯度较好的蓝色发光器件；其次，对电子注入材料及其对器件性能的影响进行较为系统的研究，提出了适当的模型对注入机理作出了尝试性解释；另外，以磷光材料为基础制备了高效率高色纯度的红色有机发光器件，并对器件发光机理进行了研究。 （1） 在蓝色发光器件的研究中，首先在以8-羟基喹啉金属配合物——LiBq₄为发光层的器件中，重点研究了作为电子传输层的Alq厚度对器件发光光谱、电流—电压特性的影响，结果表明电子传输层的厚度为5 nm时，既可以避免电子传输层的发光，又可以降低器件的工作电压，并从机理上进行了分析。接着以具有高荧光效率的DSA衍生物苯乙烯蓝色掺杂剂BCzVB为发光体，选用CBP作基质进行掺杂，得到了最大外量子效率为2.6％的色纯度很好的蓝色发光器件，色坐标为x=0.15，y=0.16，最高亮度达到8500 cd／m²。在进一步的实验中，在电子传输层与发光层之间引入BAlq来提高电子注入，将器件量子效率提高到3.3％，最高亮度达到11000 cd／m²，而器件的色纯度没有受到影响。通过对光致发光实验结果的分析表明器件的发光来源于能量传递和掺杂剂分子对载流子的直接俘获，但是后者起了主导作用。最后以TPD为空穴传输层，DPVBi为发光层，Liq／Al为复合电极实现了外量子效率为1.5％，色坐标为x=0.16，y=0.16的单异质结蓝色有机电致发光器件，并与有电子注入层的器件进行了比较。 （2） 在电子注入材料的研究中，以有机材料——Liq和无机材料——LiF为电子注入层与稳定金属Al配合构成复合电极，考查了Liq和LiF厚度对Alq发光器件的效率及电流-电压特性的影响。实验表明Liq或LiF厚度大约为0.5 nm左右时2003年上海大学博十学位论文器件的性能最佳，且使用注入层厚度约为0.5 nm的Liq器件与使用同样厚度LIF的器件性能相当，比只使用Al作电极的器件亮度和效率提高大约3倍。当改变注入层Liq或LIF的厚度时一，器件电致发光效率均随Liq或LIF厚度的增加而下降，同时一定电流下器件的工作电压随Liq或LIF厚度增加而升高，导致器件性能变差。但相对于以LIF为注入层的器件来说，以Liq为注入层器件的效率对注入层厚度表现出较低的敏感性。采用偶极模型对于电子注入的机制进行了分析解释。另外当把Liq和LIF作电子注入材料用于DPVBi蓝色发光器件及MEH一PPV橙色聚合物发光器件时，在没有电子传输层情况下Liq和LIF均能够有效的注入电子，但以Liq为电子注入层的器件其性能要优于以LIF为电子注入层的器件。 （3）以高效红色磷光材料一一苯基噬吩毗陡和乙酞丙酮与Ir的配合物btP2lr（acac）为磷光掺杂剂，以CBP为基质，制备了掺杂型器件，以期获得btP2Ir（acac）的磷光发射。在直接以Alq为电子传输层和空穴激子阻挡层时，器件最大量子效率为4.6%，最高亮度为7850 cd/m2;当在电子传输层和发光层间引入BAlq作激子空穴阻挡层时，器件的效率得到明显提高，最大效率达到7.0%，最高亮度达到1 0362ed/m2，而器件的驱动电压没有明显提高。无论是有BAlq还是没有BAlq的器件，它们的色度均非常理想，色坐标在x=0.668，y=o.325附近（非常接近NTSC标准:。。.670，，，二0.330）。光致发光对比分析表明基质CBp和掺杂剂btpZlr（aeae）之l旬存在有效的能量传递，这是确保器件发光色度纯正的基础。另外，通过对只有一种载流子的器件研究分析了掺杂体系CBP:btp2lr（acac）中载流子的注入输运特点，从中确证在掺杂型器件中存在掺杂剂分子对载流子的直接俘获。更多还原

【Abstract】 Organic thin film electroluminescence (EL), as new research field, has been a hot subject in flat panel displays and attracted more and more people. Higher and higher technology for information display is required as a result of rapid development of information technology. Display panel with rich color, low cost, environmentally protection, lightweight, even flexibility, has become a goal of modern people. Organic thin film electroluminescence would be an ideal technology for information display of modern times due to its low driving voltage, highly efficient luminescence, rich color, fast response, wide viewing angle, portability, etc. However, organic electroluminescence is by itself a subject relate to chemistry, material, physics, electronics etc., and need people to investigate it from material design and synthesis, device fabrication and its performance measurement, luminescence process and mechanism, etc.In this dissertation, main study is on device structure, performance and luminescence mechanism etc. of organic light emitting diodes (OLEDs). Firstly, several blue OLEDs are investigated and highly efficient blue OLEDs with good color purity are obtained; secondly, electron injection materials and its effect on the OLED performance are systematically investigated, and a proper model is in an attempt to explain the underlying mechanism; thirdly, highly efficient red OLEDs with high color purity are fabricated based on phosphorescent material and luminescent mechanism is studied.(1) In the study of blue OLEDs, firstly, device using lithium tetra-(8-hydroxy-quinolinato) boron (LiBq4) as an active layer was prepared and effects of electron transporting layer tris-(8-hydroxy-quinolinato) aluminum (Alq) on EL spectra and current-voltage characteristics are investigated. Experimental results show that operating voltage of the device may be lowered without emergence of luminescence of Alq as the thickness of Alq equals 5 nm. The mechanism of Alq’s effect on the device performance is also discussed. The following experiment is fabrication of blue OLEDs with good color purity using l,4-bis[2-(3-N-ethylcarbazoryl)vinyl]benzene (BCzVB) doped into 4,4’-N,N’-dicarbazole-biphyenyl (CBP). Maximum luminance and externalefficiency are 8500 cd/m2 and 2.6%. Commission Internationale de 1’Eclairage (CIE) co-ordinates are x=0.15, y=0.16. These values are further improved by inserting bis(2-methy]-8-quinolinato)4-phenylphenolate aluminum (BAlq) between CBP:BCzVB and Alq layers to be 11000 cd/m2, and 3.3%, with little variance of CIE co-ordinates. The analysis of photoluminescence spectra reveals that the emission originates from energy transfer and carrier trapping, while the latter dominates. Finally, single hetero structure blue OLED using TPD as a hole transporting layer, DPVBi as an emissive layer is realized and compared with the conventional device using Alq as an electron transporting layer. Maximum external efficiency and the CIE co-ordinates are 1.5%, x=0.16, y=0.16, respectively.(2) In the study of electron injection material, composite cathodes using organic material, 8-hydroxy-quinolinato lithium (Liq) and inorganic material, LiF and stable metal Al, were used in Alq based devices, and effects of the thicknesses of Liq and LiF on the luminescent efficiency and current-voltage characteristics of the.device are investigated. Experimental results show that the device performance is optimal when the thickness of Liq or LiF equals about 0.5 nm, and the device performance of 0.5-nm-thick Liq device is similar to that of 0.5-nm-thick LiF device, but their luminance and efficiency is several times higher than that of the device with an Al only cathode. As the thickness of Liq or LiF layer increases, the current density-voltage curves shift to higher voltage range and the efficiencies are lowed in both cases, resulting in deterioration of the device performance. But performance of the device using Liq as an electron injection layer is less sensitive in efficiency to Liq thickness than that using LiF. A dipole model is更多还原