Synthesis and Photoelectrical Properties of Room-Temperature Phosphorescent (ppy)<sub>2</sub>Ir(pybi) Complex

Abstract

A blue-green emitter of iridium(III) complex (ppy) 2 Ir(pybi), has been synthesized (ppy= 2-phenyridine and pybi=2-(2-pyridyl)benzimdazole) and its structure was characterized by Fourier transform infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance ( 1 H NMR), mass spectroscopy (MS), and elemental analysis. Its photophysical properties and energy-level structure were studied by UV-Vis absorption, excitation and emission spectroscopy, and cyclic voltammetry combining time- dependent density functional theory (TD-DFT). The electrophosphorescent performance of (ppy) 2 Ir(pybi) was characterized by using 4,4 -bis(9-carbazolyl)-1,1 -biphenyl (CBP) as host. The results indicated that the UV-Vis absorption bands were located at 250, 295, 346, and 442 nm, which were in good agreementwith the TD-DFT simulation results. The blue-green phosphorescent emission was observed with peaks at 495, 518 nm in CH 2 Cl 2 solution at room temperature. The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) energy levels and optical gap were -6.11, -3.43, and 2.68 eV, respectively. Theoretical calculation revealed that the HOMO for (ppy) 2 Ir(pybi) was mainly distributed on the ppy ligand and the iridium ion, whereas the LUMO was centered mainly on the pybi ligand. The device based on the system of (ppy) 2 Ir(pybi) doped into CBP has an electroluminescence (EL) spectrum with a peak wavelength of 508 nm, a maximum luminance of 8451 cd · m -2 , and a maximum current efficiency of 17.6 cd · A -1 . These investigations will provide an important experimental basis for the application of (ppy) 2 Ir(pybi) in the organic electroluminescent field.