Highly efficient blue phosphorescent iridium(iii) complexes with various ancillary ligands for partially solution-processed organic light-emitting diodes

Abstract

One homoleptic facial and five novel highly efficient blue heteroleptic iridium(III) complexes were designed and synthesized by selecting 2-(4-fluoro-3-(trifluoromethyl)phenyl)pyridine as cyclometalated ligands and 2,4-pentanedione, 2-(3-(trifluoromethyl)-1H-1,2,4-triazol-5-yl)pyridine, picolinic acid, 2-(1H-imidazol-2-yl)pyridine and 2-(1H-tetrazol-5-yl)pyridine as ancillary ligands, respectively. The alternation of ancillary ligands could finely tune the photophysical properties of the phenylpyridine-based complexes, particularly with respect to emission wavelength, photoluminescence quantum yield (Φ_PL), full width at half maximum (FWHM), etc. The phosphors designed not only exhibit excellent solubility in commonly used solvents with robust chemical stability but also show bright emissions in the pure blue region with very high absolute Φ_PL up to 0.98 in solution and relatively narrow FWHMs up to 52 nm. Furthermore, based on these highly efficient blue phosphors, high-performance partially solution-processed blue organic light-emitting diodes have been successfully fabricated. The electroluminescence peak, 1931 Commission Internationale de L’Eclairage coordinate and FWHM of the device based on Ir4 are all superior to the device based on FIrpic. In addition, the maximum efficiencies of the device based on Ir4 (21.15 cd A⁻¹, 12.07 lm W⁻¹) are also higher than those of the device based on FIrpic (18.89 cd A⁻¹, 11.26 lm W⁻¹) under the same conditions.