【作者】 刘刚；

【导师】 杨伟；

【作者基本信息】 华南理工大学 ， 高分子化学与物理， 2011， 博士

【摘要】 有机电致发光二极管由于在平板显示及白光照明领域的应用潜力而引起了人们的广泛关注。其中,电子由电极注入,即电子注入,是非常重要的研究课题。通常情况下,可使用低功函的金属,如Ba、Ca、Mg等提高电子的注入。但这些元素对水、氧特别敏感,环境稳定性差。因而,利用阴极界面材料,提高在环境中较为稳定的金属,如Al、Ag、Au等的电子注入性能,显得尤为重要。目前,研究较多的阴极界面材料,包括纯粹的无机盐、有机共轭聚合物电解质或一些非离子型的小分子化合物、聚合物。本文的研究集中在制备和表征新型可溶液加工的小分子电子注入/传输材料方面。我们首次合成了含有枝状芳基单元的单铵基离子分子玻璃材料,命名为glass-1。该分子离子玻璃合成简单、容易纯化,并且在甲醇中具有非常好的溶解性;譬如:室温下,10 mg分子离子盐易溶于1 ml甲醇中,因而可以方便地从醇溶液中成膜。以该分子离子材料为电子注入/传输层的聚合物绿光器件ITO/PEDOT:PSS/P-PPV/glass-1/Al,最大电流效率达12.2 cd A-1,是纯Al器件的43倍,并接近Ba/Al器件的水平。在此基础上,设计制备了一系列含有线型共轭单元的单铵基分子离子盐,命名为1a/1b和2a/2b。通过在芴的9位上引入刚性的苯基单元,成功地将结晶态的1a/1b转变成无定形态的2a/2b,并且使离子盐在醇类溶剂中的溶解度也有了很大的提高。在阴离子相同的前提下,含有线性共轭单元的单铵基分子离子盐2a、2b表现出比含有枝状芳基单元的离子盐更好的器件性能。此外,我们还研究了阴离子的改变对材料自身及器件性能的影响。如材料的分解温度、溶解度、器件的稳定性。在对单铵基离子盐研究的基础上,设计合成了两组基于双铵基的离子盐,命名为dBr-1/dBF₄-1和dBr-2/dBF₄-2。相对于dBr-1/dBF₄-1,端基为3-（4-仲丁氧基苯基）-5-（1-萘基）苯基的dBr-2/dBF₄-2表现出更好的醇溶性。以小分子绿光材料为发光层,比较了双铵基离子盐dBF₄-2和单铵基离子盐2b作为电子注入/传输层的器件的电致发光性能。发现两者均能有效提高电子的注入/传输,并且器件性能和Ba/Al作为阴极的器件相当。为避免离子迁移对器件性能造成的潜在影响,设计合成了两个非离子型的电子注入/传输材料,分别用代号PA-1和PA-2表示。化合物PA-1和PA-2分别是基于二胺和三胺基的树枝状中性小分子。以PA-2为电子注入/传输层、高功函数金属Al为阴极所构成的小分子绿光器件,获得了10.6 cd A^-1的最大电流效率。更多还原

【Abstract】 Because of the potential applications in flat panel displays and solid-state lighting, organic light-emitting diodes （OLEDs） have drawn greet attention. For OLEDs, efficient electron injection from various metal cathodes has been a subject of intensive research. The early OLEDs have used low work-function metals such as Ca and Mg as efficient cathodes. However, these metals are very sensitive to both moisture and oxygen. Thus it is very important to develop new cathode buffer materials that are capable of facilitating electron injection from more environmentally stable metals such as Al, Ag or Au. Up to now, a variety of electron-injection materials including inorganic salts, conjugated polyelectrolytes and non-ionic molecules or polymers have been reported. This thesis mainly focuses on the synthesis and characterization of new solution processable small molecular electron-injection moleculars.We first reported a monoammonium-based molecular glass containing a rigid and bulky branched aromatic unit, namely glass-1. It can be facilely synthesized and purified, showing good solubility in methanol. For instance, 10 mg of the sample can be readily dissolved in 1 ml of methanol at room temperature, so it can be processed from methanol solution. With this monoammonium salt as electron injection layer, a polymer yellow-green light-emitting device （ITO/PEDOT:PSS/P-PPV/glass-1/Al） shows a maximum current efficiency of 12.2 cd A-1, almost forty-two times higher than the bare Al device, which is comparable to that of the Ba/Al device.Further, we designed and synthesized a series of molecular monoammonium salts based on a linearπ-conjugated unit, namely 1a/1b and 2a/2b. Replacement of the ethyl groups in 1a/1b by ethoxyphenyl substituents at one of the two fluorenyl moieties can improve the solubility in methanol and promote glass formation of compounds 2a/2b. It has been found that 2a and 2b show better device performances than 1a and 1b, respectively. In addition, the counteranion has an important effect on the device performances of the OLEDs as well as on solubility and thermal properties of the resulting ionic salts. ?Based on the above monoammonium salts, we developed two types of bis-ammonium salts, namely dBr-1/dBF₄-1 and dBr-2/dBF₄-2. Compared to dBr-1/dBF₄-1, compounds dBr-2/dBF₄-2 containing 3-（4-sec-butoxyphenyl）-5-（1-naphthyl）phenyl substituents show better solubility in alcohol. The green light-emitting OLEDs based on the bis-ammonium salt dBF₄-2 and monoammonium salt 2b as the electron-injection layers and Al as the cathode show comparable performances.We have also designed and synthesized two non-ionic molecules, which were named as PA-1 and PA-2. Compounds PA-1 and PA-2 are based on diamine and triamine, respectively. The green light-emitting device with PA-2 as the electron-injection/transport layer and high work-function metal Al as cathode revealed a maximal efficiency of 10.6 cd A^-1.更多还原