Enhanced light emission from phosphorescent single-layered organic light-emitting devices doped with ionic salt by simultaneous thermal and electrical annealing

摘要

We studied the effect of thermal and electrical annealing on the light emission of phosphorescent single-layered organic light-emitting devices (PHOLEDs) doped with ionic salt. From the annealed green PHOLEDs with only an Al cathode, we clearly observed homogeneous and enhanced electrophosphorescent emission over ～50 000 cd/m~2. The efficiency of the device was also improved. The device operates at relatively low voltages and achieves a high peak current efficiency of over 30 cd/A, even at 1000 cd/m~2. These improved characteristics regarding luminescence and efficiency indicate clearly that simultaneous annealing can induce proper adsorption of charged salt ions at the electrode surfaces. This adsorption will lead to an increased and balanced injection of carriers.