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/m 2 . By the device analysis including time-resolved electroluminescence measurements, it was confirmed that TTA contributes to the high efficiency.

We developed a high‐performance 3.4‐in. flexible active‐matrix organic light‐emitting diode (AMOLED) display with remarkably high resolution using an oxide semiconductor in a backplane, by applying our transfer technology that utilizes metal separation layers. Using this panel, we also fabricated a prototype of a side‐roll display for mobile uses. In these AMOLED displays, a white OLED combined with a color filter was used in order to achieve remarkably high resolution. For the white OLED, a tandem structure in which a phosphorescent emission unit and a fluorescent emission unit are serially connected with an intermediate layer sandwiched between the emission units was employed. Furthermore, revolutionary technologies that enable a reduction in power consumption in both the phosphorescent and fluorescent emission units were introduced to the white tandem OLED.

This paper discusses the effectiveness of energy transfer from an exciplex to an emitter in both phosphorescent and fluorescent organic light‐emitting diodes. This energy transfer enhances the efficiency, lowers the drive voltage, and extends the lifetime. The increase in the quantum efficiency of a fluorescent organic light‐emitting diode using this mechanism is also analyzed.

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By developing low‐refractive‐index organic hole‐ and electron‐transport materials enabling the efficiency (cd/A/CIEy) of a top‐emission blue fluorescent OLED to be increased by 12% and 11%, respectively, the blue fluorescent OLED has achieved the ultra‐high efficiency over 250 ca/A/CIEy without the need of a special light‐outcoupling structure or film.