有机吡啶盐的电致发光

有机盐是一种离子化合物,其分子间依靠比范德瓦尔斯力大得多的离子键结合,这有利于器件稳定性的提高。主要研究一种以新型有机吡啶盐ASPT(trans-4-P-(N-ethyl-N-(hydroxylethyl)-amino)styryl]-N-methylpyridinium tetraphenyl-borate)作发光层的有机电致发光特性。实验发现有机盐ASPT是一种性能较好的红光发射材料。利用ASPT作发光层的单层电致发光器件,可获得稳定的红色电致发光。通过对外场界面势垒影响分析,我们讨论了这种单层器件的发光机理。为了探索ASPT中载流子传输与复合过程,并提高器件性能,设计了ASPT/Alq₃双层和TPD/ASPT/Alq₃三层结构的器件,进一步研究了它们的光电特性。实验结果表明,利用双层器件可获得亮度较高的红色发光。而在三层器件中,由于不同功能层的载流子传输特性的差别,激发复合区域受到驱动电压的显著影响,因此电致发光光谱随电压的变化而变化。通过对光谱结构、能级位置的分析,讨论了相关的发光机理。

Electroluminescence of an Organic Pyridyl Salt

Improvement of the triple colors,red,green and blue is the most basic and the most important technology for full color display.Green and blue emission from the organic light emitting diodes(OLED)have been employed successfully to organic display,but the red light performance still need to improved.So far,host-guest system and rare earth complexes were used for red emission.In these two kinds of OLEDs,the energy transfer efficiency were generally limited by the concentration quenching and the phase separation.Ones have paid great effort to explore some novel materials and devices structures for red emission with high perfor-mance.In this paper,an ionic organic pyridyl salt ASPT(trans-4-P-(N-ethyl-N-(hydroxylethyl)-amino)styryl]-N-methylpyridinium tetraphenyl-borate)] was employed as active layer for an organic light-emitting diode with stable red emission.The investigation on the electroluminescent properties demonstrated that ASPT is a good luminescent molecule for red emission.A stable red electroluminescence was obtained by using this material as emitting layer in a monolayer structure.The luminescence mechanism was discussed based on the influence of the external electrical field on the energy barrier in the interfaces between the active layer and the electrodes.In order to understand the charier charge transport and their recombination process,and to improve the EL performance,double-layer TPD/ASPT or ASPT/Alq_3 and triple-layer TPD/ASPT/Alq_3 structures were designed and the EL properties were further studied.Brighter red EL and red-blue variable emission depended on the applied voltage were observed in the double-layer and the triple-layer structures,respectively.Consi-dering the different function of each layer in the triple-layer structure,the color variation is assumed to the change of the recombination region.The mechanism was discussed by analyzing the spectra and the corresponding energy level structures.