Rational Design and Characterization of Heteroleptic Phosphorescent Complexes for Highly Efficient Deep-Red Organic Light-Emitting Devices

摘要

Two new deep-red iridium(III) complexes, (fpiq)(2)Ir(dipba) (fir1) and (f(2)piq)(2)Ir(dipba) (dflr2), comprising two cyclometaling ligands of fluorophenyl-isoquinoline derivatives (fpiq and f2piq) and a N-heterocyclic tarbene (NHC)-based ancillary ligand of N,N'-cliisopropylbenzamidinate (dipba) are designed, synthesized, and characterized. Given the unique four-membered Ir-N-C-N backbone built by the metal center and the ancillary ligand, both phosphors achieve significant improvement for their comprehensive optoelectronic characteristics. Density function theory (DFT) calculations and electrochemical measurements sup= port the genuine pure red phosphorescent emission of On and dflr2 based on their clearly distinct electron density distributions of the HOMO/LUMO orbitals compared with other red-emitting Ir(III) derivatives. Both new phosphors show deep-red" emission with lambda(max) values in the region of 650-660 nm with high PLQYs and short.-excited-state lifetimes. The phosphorescent organic light emitting diodes (PhOLEDs) based on flr-1 and dflr2 realize deep-red EL with-the stable ClEx,y coordinates of (0.70, 0.30) and (0.69, 0.31), the peak EQB/PE values, of 15.4%/9.3 lm. w(-1) and 16.7%/10.4 lm respectiyely, which maintain such high levels- as 10.6%/3.5 lm-W and 10.8%/3.6 lm W-1 at the practical himinance of 1000' cd m(2). They are the highest EL values reported for the OLEDs with such deep-red CIE coordinates.