| 초록 |
A homoleptic and two new heteroleptic blue emitting Ir(III) complexes, tBu-FCNIr and tBuCN-FIracac/EtOCN-FIracac consisting of 2′,4″-difluorophenylpyridine (dfppy) with cyano (CN) group at 5′-position of the phenyl and tert-butyl (tBu) or ethoxy (EtO-) group at 4-position of the pyridine as main ligand are synthesized and characterized for phosphorescent organic light-emitting diodes (PhOLEDs). The tBuCN-FIracac and EtOCN-FIracac demonstrated high PLQYs of 90 ± 3% and 82 ± 3%, respectively, whereas tBu-FCNIr shows relatively low PLQY of 61 ± 3% measured in thin film. The emission spectra of EtOCN-FIracac, tBuCN-FIracac and tBu-FCNIr represent substantial mixing of lower energy 3MLCT and 3LC excited states. The PhOLEDs based on tBuCN-FIracac and EtOCN-FIracac show one of the highest efficiencies ever achieved for blue color with a maximum EQE of 22.3% (39.2 cd A-1) and 21.5% (35.1 cd A-1), respectively with a simple device structure; while the similar device based on tBu-FCNIr display a maximum EQE of 16.2% (23.5 cd A-1). |
