High‐Efficiency Blue Hyper‐TTF OLEDs Formed by Pyrene‐Carbazole Derivatives as Triplet Donor

Triplet–triplet fusion (TTF) is one of the efficient methods to harvest low‐energy triplet excitons to become high‐energy singlet emission and achieve excellent performances in blue organic light‐emitting diodes (OLEDs). Further progress, an advanced approach is Hyper‐TTF OLED by utilizing bi‐emitting‐layers (bi‐EMLs) to separate the charge recombination zone and TTF zone to prevent triplet exciton and polaron quenching. The bi‐EML mainly involves pyrene and anthracene derivatives. The novel pyrene derivatives, PPCbz and PPtCbz , constructed with pyrene and carbazole, are successfully synthesized. In the bi‐emitting‐layer structure, the PPCbz and PPtCbz are respectively employed as the host for the carrier recombination and exciton generation layer, in which singlet excitons can be rapidly transported to the emitters, and the triplet excitons can be triaged to the adjacent TTF layer for luminescence. The blue Hyper‐TTF OLED of PPCbz achieves an exceptionally high external quantum efficiency ( η EQE ) of 16.3%, representing the record‐high η EQE value among the reported blue TTF OLEDs. It can also be applied to deep blue emission by incorporating a blue MR‐TADF emitter, achieving a device performance with a narrow emission bandwidth of 22 nm, CIE coordinates of (0.131, 0.084), and an η EQE of 12.1%.