Deep Blue Emitter Based on Tris(triazolo)triazine Moiety with CIEy < 0.08 for Highly Efficient Solution‐Processed Organic Light‐Emitting Diodes Via Molecular Strategy of “Hot Excitons”

Abstract Realizing high efficiency deep blue emission with a Commission international de I'Eclairage (CIE) coordinate of CIE y < 0.08 is still a big challenge. In this contribution, three molecules, named TTT‐TPA‐R (R = H, OMe, t Bu), using tris(triazolo)triazine (TTT) as the acceptor and triphenylamine derivatives (TPA‐R, R = H, OMe, and t Bu) as the donor are prepared and characterized. All these emitters show deep/pure blue emission between 420 and 470 nm in the PMMA film, concomitant with the excellent emission efficiency of 80–100%. Both experimental and calculated methods demonstrate that these emitters exhibit a clearly hybridized local and charge‐transfer excited state and can harvest both singlet and triplet excitons via reverse intersystem crossing process from the high‐lying triplet to singlet states. Therefore, the solution processable deep blue organic light‐emitting diodes (OLEDs) achieve a maximum external quantum efficiency ( EQE max ) of 10.5% which is the recorded value for the solution processable deep blue OLED based on the “hot exciton” mechanism. Using TTT‐TPA‐H as the host material, solution‐processed phosphorescent OLED based on PO‐01 presents the EQE max of 20.2%. These results pave a novel avenue for designing highly efficient deep blue emitter in solution processable OLED.