High-Performance Red, Green, and Blue Electroluminescent Devices Based on Blue Emitters with Small Singlet-Triplet Splitting and Ambipolar Transport Property
High-Performance Red, Green, and Blue Electroluminescent Devices Based on Blue Emitters with Small Singlet-Triplet Splitting and Ambipolar Transport Property
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DOI：
10.1002/adfm.201202981
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发表时间：
2013-06-06
影响因子：
19
通讯作者：
Wang, Yue
中科院分区：
文献类型：
--
作者：
Wang, Kai;Zhao, Fangchao;Wang, Yue
设计、合成了两种配位配合物的发射体以及宿主材料Be(PPI)2和Zn(PPI)2 （PPI = 2-（1-苯基- 1h -菲罗[9,10-d]咪唑-2-基）苯酚）。金属原子的掺入使Be(PPI)2和Zn(PPI)2在475℃和217℃左右的热稳定性得到改善，从而形成了扭曲构象和刚性分子结构。给电子苯酚基团的引入导致发射色向深蓝色区域移动，发射最大值出现在429nm左右。这种分子设计策略确保了Be(PPI)2和Zn(PPI)2的最高已占据分子轨道（HOMO）和最低未占据分子轨道（LUMO）的HOMO和LUMO定位在分子的不同部分。因此，这两种配合物具有双极性输运性质和较小的单重态-三重态分裂，Be(PPI)2为0.35 eV, Zn(PPI)2为0.21 eV。一种以Be(PPI)2为发射体的未掺杂的深蓝色荧光有机发光器件（OLED），其最大功率效率为2.5 lm W-1， CIE坐标为（0.15,0.09），非常接近美国国家电视标准委员会（NTSC）的蓝色标准（CIE: 0.14, 0.08）。以Be(PPI)2和Zn(PPI)2为主体材料的绿色和红色磷光oled （PhOLEDs）表现出高性能。绿色二极管的最高功率效率为67.5 lm W-1，红色二极管的最高功率效率为21.7 lm W-1。此外，基于Be(PPI)2的器件表现出低效率滚转行为，这归因于Be(PPI)2更平衡的载流子输运特性。
Two coordination complex emitters as well as host materials Be(PPI)2 and Zn(PPI)2 (PPI = 2-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenol) are designed, synthesized, and characterized. The incorporation of the metal atom leads to a twisted conformation and rigid molecular structure, which improve the thermal stability of Be(PPI)2 and Zn(PPI)2 with high Td and Tg at around 475 and 217 degrees C, respectively. The introduction of the electron-donating phenol group results in the emission color shifting to the deep-blue region and the emission maximum appears at around 429 nm. This molecular design strategy ensures that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) HOMO and LUMO of Be(PPI)2 and Zn(PPI)2 localize on the different moieties of the molecules. Therefore, the two complexes have an ambipolar transport property and a small singlet-triplet splitting of 0.35 eV for Be(PPI)2 and 0.21 eV for Zn(PPI)2. An undoped deep-blue fluorescent organic light-emitting device (OLED) that uses Be(PPI)2 as emitter exhibits a maximum power efficiency of 2.5 lm W-1 with the CIE coordinates of (0.15, 0.09), which are very close to the National Television Standards Committee (NTSC) blue standard (CIE: 0.14, 0.08). Green and red phosphorescent OLEDs (PhOLEDs) that use Be(PPI)2 and Zn(PPI)2 as host materials show high performance. Highest power efficiencies of 67.5 lm W-1 for green PhOLEDs and 21.7 lm W-1 for red PhOLEDs are achieved. In addition, the Be(PPI)2-based devices show low-efficiency roll-off behavior, which is attributed to the more balanced carrier-transport property of Be(PPI)2.