A highly efficient host/dopant combination for blue organic electrophosphorescence devices

作者：Lin Jin Ju^*; Liao Wei Shieng; Huang Hsiang Jung; Wu Fang Iy; Cheng Chien Hong

来源：Advanced Functional Materials, 2008, 18(3): 485-491.

DOI：10.1002/adfm.200700537

We have synthesized a new blue-emitting iridium complex, FIrpytz (iridium(III) bis(4,6-difluorophenylpyridinato)-4-(pyridin-2yl)-1,2,3-triazolate), and two new bis(triphenyisilyl) derivatives, BSB (4,4'-bis-triphenylsilanyl-biphenyl) and BST (4,4 ''-bis(triphenylsilanyl)-(1,1',4',1 '')-terphenyl) as hosts for blue phosphorescence devices. The photoluminescence (PL) and electroluminescence (EL) properties of different host/dopant combinations were studied in details. These two arylsilanes showed glass transition temperatures (T(g)s) >= 100 degrees C higher than those of UGH1 (diphenyl-di(o-tolyl)silane) and UGH2 (1,4-bis(triphenylsilyl)benzene), the common arylsilane-based hosts. The band gaps for BSB and BST are 4.16 and 3.78 eV, respectively, lower than that of UGH2 of 4.40 eV. The FIrpytz-doped UGH2, BSB and BST films exhibit PL quantum yields of 0.58, 0.83 and 0.48, respectively. The EL devices using FIrpytz or FIrpic (iridium(III) bis(4,6-difluorophenylpyridinato)-picolinate) as the blue phosphorescence dopants and UGH2, BSB and BST as the hosts also showed that BSB-based devices gave the best device efficiencies. Both PL and EL studies show that BSB is better than UGH2 and BST as the host material for FIrpytz and FIrpic. In particular, the use of Flrpytz as dopant, BSB as host and LiF/Al as cathode provides a remarkably efficient combination for blue electrophosphorescence device reaching a very high external quantum efficiency of 19.3% at 8.5 V and a high luminance level of 20500 cd m(-2) at 19.3 V after electroluminescence started at 5.1 V.

• 出版日期2008-2-11
• 单位清华大学