Efficient blue organic light-emitting diodes with low operation voltage by improving the injection and transport of holes

Abstract In this work, we reported the highly efficient organic electroluminescent (EL) devices based on blue phosphorescent material FIr6. By utilizing p-type dopant HAT-CN as hole injection layer material, the injection of holes from the anode was significantly improved. In addition, doping HAT-CN into hole transport layer (HTL) and inserting thin TcTa film between HTL and light-emitting layer (EML) improved the transport of holes. The stepwise energy levels between functional layers reduced the injection barriers of carriers, thus improving the balance of carriers within EML. Finally, highly efficient blue EL device realized the maximum current efficiency, power efficiency, external quantum efficiency (EQE) and brightness up to 39.14 cd/A, 38.68 lm/W, 24.6% and 17201 cd/m2, respectively. Even at the high brightness of 1000 cd/m2 (3.7 V), current efficiency and EQE as high as 36.73 cd/A and 23.1%, respectively, can still be retained by the same device. Our investigation provides an idea for the design of high-performance devices with low operation voltage and slow efficiency roll-off.