High-brightness solution-processed phosphorescent OLEDs with pyrimidine-based iridium() complexes

Two heteroleptic cyclometalated iridium( iii ) complexes, Ir(ppm) 2 (pic) and Ir(ppm) 2 (taz), using 4,6-diphenyl pyrimidine (Hppm) as a cyclometalating ligand, were successfully synthesized and characterized. Strong emission at 555 and 532 nm with high photoluminescence quantum yields of 83% and 86% in PMMA at 298 k were obtained for Ir(ppm) 2 (pic) and Ir(ppm) 2 (taz), respectively. Solution-processed organic light-emitting diodes (OLEDs) based on Ir(ppm) 2 (pic) and Ir(ppm) 2 (taz) showed high-brightness of 112233 and 125072 cd m 2 , peak current efficiencies of 30.6 and 40.4 cd A 1 and maximum external quantum efficiencies of 10.4 and 17.3%, respectively, accompanied by very low efficiency roll-off values. The ancillary ligand taz tuned the emission to saturated green, and more importantly, it can significantly increase the spectral stability and device efficiency. New complexes Ir(ppm) 2 (pic) and Ir(ppm) 2 (taz) emitted 555 and 532 nm light, respectively. Solution-processed organic light-emitting diodes based on Ir(ppm) 2 (taz) showed high-brightness of 125072 cd m 2 , peak current efficiencies of 40.4 cd A 1 .