A thermally activated delayed fluorescence exciplex to achieve highly efficient and stable blue and green phosphorescent organic light-emitting diodes.

The development of a thermally activated delayed fluorescence (TADF) exciplex with high energy is of great significance in achieving highly efficient blue, green, and red organic light-emitting diodes (OLEDs) for use in full-color displays and white lighting. Highly efficient and stable blue and green phosphorescent OLEDs were demonstrated by employing a TADF exciplex (energy: 2.9 eV) based on 4-substituted aza-9,9'-spirobifluorenes (aza-SBFs). Blue PhOLEDs demonstrated a maximum current efficiency (CE) of 47.9 cd A ^-1 and an external quantum efficiency (EQE) of 22.5% at 1300 cd m ^-2 (2.5 times the values of aza-SBF-based systems), with the best blue PhOLED demonstrating a CE, power efficiency (PE) and EQE of 60.3 cd A ^-1 , 52.7 lm W ^-1 , and 26.2%, respectively. Green PhOLEDs exhibited a CE of 78.1 cd A ^-1 and EQE of 22.5% at 9360 cd m ^-2 , with the best green PhOLED exhibiting a maximum CE, PE, and EQE of 87.4 cd A ^-1 , 101.6 lm W ^-1 , and 24.5%, respectively. The device operational lifetime was improved over 17-fold compared to reference devices because of the high thermal stability of the materials and full utilization of the TADF exciplex energy, indicating their potential for application in commercial OLEDs.
Competing Interests: There are no conflicts to declare
(This journal is © The Royal Society of Chemistry.)