蓝色有机发光材料LiBq4的合成及其发光特性

蓝色有机发光材料的开发对于实现有机发光二极管(OLED)的全彩色化具有十分重要的意义.报道了蓝色有机发光材料8-羟基喹啉硼化锂(LiBq₄)的合成及提纯,研究了LiBq₄的光致发光特性,并用LiBq₄作为发光材料制备了蓝色有机发光器件,研究了电子传输层Alq₃的厚度及空穴缓冲层CuPc对器件电流-电压和亮度-电压特性的影响.结果表明,LiBq₄的光致发光峰值波长为452nm,器件ITO/PVK:TPD/LiBq₄/Alq₃/Al的电致发光光谱峰值波长位于475nm处,在25V工作电压下其最高亮度约为430cd/m².但CuPc的加入加剧了器件中载流子的不平衡注入,导致器件性能恶化.通过调整Alq₃的厚度,同时在Alq₃和Al阴极之间加入LiF薄膜以提高电子注入效率,获得了较为理想的实验结果.

Synthesis and Luminescence Properties of Blue Organic Light-emitting Material LiBq4

Synthesis of blue organic light-emitting materials is very important for practical applications of organic light-emitting diodes(OLEDs).Organometallic complex lithium tetra-(8-hydroxy-quinolinato)boron(LiBq₄)was synthesized,purified and used as light-emitting material.Blue ITO/PVK:TPD/LiBq₄/Alq₃/Al OLED was fabricated adopting spin and vacuum deposition,and the electroluminescence spectrum was measured at different operation volta】ge.At the same time,the influence of thickness of Alq₃,CuPc and LiF on the luminescence properties of blue OLEDs was studied.Results indicated that,the peak wavelength of fluorescence spectrum for LiBq₄ is about 452 nm under excitation of 350 nm.The peak wavelength of electroluminescence spectrum for blue OLED ITO/PVK:TPD/LiBq₄/Alq₃/Al device locates at 475 nm,and one weak shoulder peak appears at about 500 nm,this is resulted from excitation of Alq₃.The luminance of this blue OLED can reach 430 cd/m² at 25 V operate voltage.As electron transfer material,the thickness of Alq₃ film has distinct influence on the electroluminescence spectra and luminance of blue OLEDs.Through adjusting the thickness of Alq₃ layer,the recombination region of holes and electrons can be restricted in LiBq₄,and the shoulder peak will weaken and disappear.The optimal thickness of Alq₃ film is about 10 nm.Although the addition of CuPc between ITO and PVK:TPD could enhance the injection ability of holes,simultaneously induces the imbalance injection of charge carriers,and deteriorates the properties of blue OLED.The addition of LiF thin film between Alq₃ and Al cathode could enhance the injection ability of electrons,and makes the injection of electrons reach equilibrium with holes.So the recombination probability of holes and electrons was improved and the luminance of blue OLED was improved evidently.These results were explained with the schematic energy level structure of the blue OLEDs.