利用溶液製程製作小分子磷光藍光與單發光層磷光白光之高效率有機發光二極體

Abstract

經由蒸鍍製程所製作的有機發光二極體，在大面積元件製作以及卷對卷製程上難以實現。為了達到低成本以及大面積元件製作的有機發光二極體，溶液製程是一個理想的方法。在這篇論文中，我們利用溶液製程刮刀塗佈方法製作小分子磷光藍光與單發光層磷光白光之高效率有機發光二極體。一般使用溶液製程的小分子有機發光二極體在電子傳輸層也還是使用蒸鍍的製程，導致製程上的複雜，而我們的元件包括電子傳輸層也是使用刮刀塗佈的溶液製程方法。為了達到高效率白光元件，我們先從提升磷光藍光FIrpic元件的效率開始，我們使用一個擁有較高三重激發態能量以及雙極性的主發光體26DCzPPy。主發光體的高三重激發態能量會使三重激發態的激子侷限在客發光體當中，而雙極性也能達到載子傳輸的平衡，進而得到高效率磷光元件。溶液製程的小分子磷光藍光元件最高電流效率達到25.1 cd/A ( 最高功率效率為9.3 lm/W )，而最高亮度為20,790 cd/m2。得到不錯效率的磷光藍光元件之後，我們加入磷光橘光發光體PO-01-TB以後得到高效率單發光層磷光白光元件，最高電流效率達到34.24 cd/A ( 最高功率效率為12.04 lm/W )，而最高亮度為27,920 cd/m2。

In general , highly efficiency organic light-emitting diodes ( OLEDs ) are fabricated by vacuum deposition . The cost for such vacuum deposition is however intrinsically high due the following reasons . The vacuum system itself for large size has a high cost and the majority of the organic semiconductors is deposited onto the chamber wall and is wasted . Therefore , solution-process is ideal candidates to fabricate low cost and large area OLEDs . In this thesis , we demonstrate high performance , single emitting layer small-molecule blue and white OLEDs via solution process by using the blade coating method . Compare with other solution-processed small-molecular OLEDs reports , an additional hole-blocking / electron-transport layer which was made by thermal vapor deposition , but our hole-blocking / electron-transport layer which were made by solution process via blade coating method . We use a host material 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine ( 26DCzPPy ) which has carbazole electron donor with high triplet energy and pyridine electron acceptor with high electron affinity to give bipolar character . The host material 26DCzPPy as a result of good confinement of the triplet excitons on the guest molecules in the emissive layer , so the devices have a good performance . A blue-phosphorescent bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium(III) ( FIrpic ) small-molecule solution-processed OLEDs shows a maximum luminance efficiency of 25.1 cd/A ( 9.3 lm/W ) , and a maximum luminance of 20,790 cd/m2 . Blue-phosphorescent ( FIrpic ) and orange- phosphorescent ( iridium(III)bis(4-(4-t-butylphenyl)thieno[3,2-c] pyridinato-N,C2’)acetylacetonate PO-01-TB ) iridium complexes were doped into the host 26DCzPPy to enable a small-molecule solution-processed white OLEDs . We demonstrate a single light emitting layer device of white emission shows a maximum luminance efficiency of 34.24 cd/A ( 12.04 lm/W ) , and a maximum luminance of 27,920 cd/m2 .