Molecular Design of Blue Thermally Activated Delayed Fluorescent Emitters for High Efficiency Solution Processable OLED via an Intramolecular Locking Strategy

An asymmetric blue emitter of DPS-BF-Ac featuring donor-π-acceptor skeleton is prepared via intramolecular cyclization. Remarkable EQE max of ∼ 25% was achieved for the solution processed OLED, concomitant with the emission peak at ∼ 480 nm. Using DPS-BF-Ac and PO-01 as the blue and red dopant, respectively, the solution processable hybrid white OLED showed an EQE max of ∼ 29%. • Efficient blue emitter of DPS-BF-Ac is prepared via intramolecular cyclization. • A remarkable EQE max of ∼ 25% is achieved for the blue solution processed OLED. • DPS-BF-Ac based solution processable hybrid white OLED shows an EQE max of ∼ 29%. Realizing high-efficiency blue emission in solution processable organic light-emitting diodes (OLED) with thermally activated delayed fluorescent (TADF) emitters is still a big challenge. To suppress the non-radiative process in TADF emitters, compound DPS-BF-Ac featuring a donor-π-acceptor skeleton is prepared via intramolecular cyclization, in which diphenylsulfone (DPS), acridine (Ac) and furan derivatives are regarded as the donor, acceptor and π linker, respectively. Then, compounds DPS-Ph-Ac , DPS-OMe-Ac and DPS-OH-Ac with different π linkers are investigated to further explore the molecular structure-property relationships. All compounds show promising blue emission with a clear TADF character. Single crystal analysis demonstrate that compound DPS-BF-Ac possesses almost a perpendicular geometry between donor and acceptor groups and expanded molecular rigidity, leading to a smaller singlet-triplet energy difference and greatly improved emission efficiency. A remarkable external quantum efficiency ( EQE max ) of ∼ 25% is achieved for the DPS-BF-Ac based solution OLED, concomitant with the emission peak at ∼ 480 nm. Using DPS-BF-Ac and PO-01 as the blue and red dopant, respectively, the white OLED exhibit an EQE max of ∼ 29%. This research shows that intramolecular cyclization is an effective strategy for designing high efficiency solution-processable blue TADF emitters.