Efficient harvesting of triplet excitons via multiple fast TTA up-conversion and high-lying reverse intersystem crossing channels for efficient blue fluorescent organic light-emitting diodes

Abstract

The efficient harvesting of triplet excitons is key to realizing high efficiency blue fluorescent organic light-emitting diodes (OLEDs). Triplet–triplet annihilation (TTA) up-conversion is one of the effective triplet-harvesting strategies. However, during the TTA up-conversion process, a high current density is necessary due to the competitive non-radiative triplet losses. In this study, we designed blue organic light-emitting diodes with fast TTA up-conversion and high-lying reverse intersystem crossing channels. It can be seen that the utilization of triplet excitons was greatly improved and the non-radiative triplet losses were significantly suppressed due to the availability of multiple efficient channels for triplet exciton utilization. As a result, a high efficiency blue fluorescent OLED was successfully fabricated. The maximum external quantum efficiency (EQE) reached 11.4% with CIE coordinates of (0.13, 0.11). This research provides a new route for the development of high efficiency blue fluorescent OLEDs.