Highly efficient long-life blue fluorescent organic light-emitting diode exhibiting triplet–triplet annihilation effects enhanced by a novel hole-transporting material

Abstract

A novel hole-transporting material with high singlet and triplet excitation energy levels was developed. Quantum efficiency of a fluorescent organic light-emitting diode (OLED) using this material as a hole-transporting layer can be increased because of facilitated triplet–triplet annihilation (TTA) due to exciton confinement in an emission layer. Furthermore, this material has a deep highest occupied molecular orbital level because of the absence of triarylamine structure. This feature also contributes to the increase in the quantum efficiency, owing to inhibition of a low-energy exciplex formed between the material and a host in the emission layer. Achieved consequently was a blue fluorescent OLED exhibiting a high external quantum efficiency of 11.9% and a long half-decay time of 8,000 h at 1,000 cd/m2. By the device analysis including time-resolved electroluminescence measurements, it was confirmed that TTA contributes to the high efficiency.