Development of highly efficient meridional Ir(III) complexes in solution-processed green phosphorescent organic light-emitting diodes

Two highly effective homoleptic meridional ( mer ) isomer-based emitters Ir(III) complexes, mer-MECF and mer- MEMO were synthesized for use in solution-processed phosphorescent organic light-emitting diodes (PHOLEDs). Both Ir(III) complexes contained a (2-ethylhexyl group) and different functional groups, such as trifluoromethyl (-CF3) and methoxy (-OCH3) and a substituted amide-bridged phenylpyridine unit, which was utilized as a main ligand. Thermal, photochemical, electroluminescence (EL) and electrochemical properties performances were examined. Interestingly, both complexes exhibited a structureless green light emission spectrum, high photoluminescence quantum yields (PLQYs) and excellent solubility in organic solvents. The solution-processed PHOLED containing mer-MEMO as dopant exhibited an excellent external quantum efficiency of 16.5 % and a current efficiency 54.3 cd A- 1 . The electron transport layer (ETL) optimized device containing mer-MECF as dopant had an excellent external quantum efficiency of 21.1 % and a current efficiency 71.4 cd A- 1 . The study shows that the described amide-bridged mer Ir(III) complexes have potential use as solution-processed PHOLEDs.