Synthesis And Study Of Electroluminescent Properties Of Orange-emitting Irdium (Ⅲ) Complexes

White Organic light-emitting diodes (WOLEDs) are currently attracting a lot of attention due to their potential application in low-cost full color displays. Of the light-emitting materials available, phosphorescent materials are particularly promising because they can emit light from both singlet and triplet excitions, enabling the fabrication of PhOLEDs with close to 100% internal quantum efficiency. In general, WOLEDs can be obtained by incorporating either three primary colors (red, green, and blue) or two complementary color ones (e.g "blue and orange"). Two complementary colores have ascended to be one important method for fabrication of WOLEDs in a multi-structure for their simple fabrication. Therefore, although red, green and blue emitters of high color purity are required for full color display applications, there is still a great demand for emitters that give a bright color, such as orange for multiple color display purposes. In particular, the interest in phosphorescent Ir(III) complexes is growing rapidly with respect to their very high luminescence efficiencies and rather short phosphorescence lifetimes.Here, we report the synthesis, redox, photophysical, and EL properties of a new series of bifunctional bis-and tris-cyclometalated Ir(III) complexes [Ir(pcb)2(acac),Ir(pcb)3 Ir(bpp)2(acac),Ir(bpp)3] containing both hole-transporting 9-arylcarbazolyl, diphenylaminofluorene units and electrophosphorescent Ir functional units, in which the HT and electro-luminescent functional groups are integrated into one molecular unit essential for more efficient charge transport in the EL process. All compounds were purified by recrystallization or column chromatography and characterized by MS,MALDI-TOF-MS and 1H NMR. Absorption and photo luminescence (PL) spectra of the complexes were measured in CH2Cl2 and in soild state. All the complexes emit orange PL bands. The phosphorescence quantum yieleds were calculated using Ir(ppy)3 as a standard reference. To investigate the charge carrier injection properties of the Ir(III) complexes and evaluate their highest occupied molecular orbital (HOMO) and lowest unoccupiedmolecular orbital (LUMO)energy levels, we carried out redox measurements by cyclic voltammetry using ferrocene as the internal standard. All the Ir(III) complexes showed a reversible redox process, suggesting that these Ir(III) complexes stabilized the formation of both cation and anion radicals in PhOLEDs. To illustrate the EL properties of these Ir(III) complexes, PhOLEDs were fabricated using asdopants in the emission layer. These vacuum-deposited orange OLEDs using CBP as a host material show very high efficiencies. Device B exhibited a maximum luminance (Lmax) of 43510 cd/m2 at 11.5 V. Furthermore, a high luminance efficiency of 41.3 cd/A and a power efficiency of 23.9 lm/W were achieved for device B. Considering the performance advantages of these, orange phosphors, manufacturing WOLEDs using them is presently underway.