High performance organic light-emitting diodes with tunable color range from orange to warm white based on single thermally activated delayed fluorescence emitter

Abstract

In this work, we reported the highly efficient organic light-emitting diodes based on orange-emitting thermally activated delayed fluorescence emitter 1,4-dicyano- 2,3,5,6-tetrakis(3,6-diphenyl-carbazol-9-yl)benzene (4CzTPN-Ph). By utilizing the bipolar material 2,6-bis(3-(9H-carbazol-9-yl)phenyl)-pyridine (26DCzPPy) and hole type material 4,4′,4″-Tri(9-carbazoyl)triphenylamine (TcTa) as host and ladder materials, respectively, the optimized single light-emitting layer (EML) orange device obtained the maximum brightness, external quantum efficiency, current efficiency and power efficiency up to 41791 cd/m2, 13.1%, 42.97 cd/A and 44.98 lm/W, respectively. Except for the 570 nm characteristic emission, interestingly, there is another emission peak at about 475 nm, which increases rapidly with decreasing doping concentration. Therefore, device color shifts gradually from orange to warm white with decreasing doping concentration due to the increasing relative intensity of exciplex emission. Finally, warm white device (Commission Internationale de L'Eclairage (CIE) Coordinates at (0.337, 0.476)) based on single TADF emitter with the maximum brightness, external quantum efficiency, current efficiency and power efficiency up to 23560 cd/m2, 10.2%, 32.33 cd/A and 32.75 lm/W, respectively, was also obtained.