Reported herein is a molecular design strategy of deep‐blue emitters for resolving the lack of highly efficient deep‐blue organic light‐emitting diodes (OLEDs) featuring CIEy (Commission Internationale de l'Eclairage) color coordinates matching the display requirements (<0.1). The strategy is to combine weak spiro‐donor and spiro‐acceptor groups into a linear donor‐π‐acceptor type of thermally‐activated delayed fluorescence molecule through a sterically bulky π‐spacer. The strategy endows an emitter with deep‐blue emission, a narrower emission bandwidth (51 nm in toluene), a high photoluminescence quantum yield (0.95 in toluene), weak concentration quenching, and efficient triplet‐exciton utilization, which are all attractive characteristics for emitters of deep‐blue OLEDs with lower CIEy coordinates. Owing to the rational design, the emitter has realized not only highly efficient doped deep‐blue OLEDs with external quantum efficiencies (EQEs) up to 25.4 % and CIEy less than 0.1 but also so far the most efficient nondoped deep‐blue OLED (EQE up to 22.5 %) with CIEy less than 0.1.
Reported herein is a molecular design strategy of deep‐blue emitters for resolving the lack of highly efficient deep‐blue organic light‐emitting diodes (OLEDs) featuring CIEy (Commission Internationale de l'Eclairage) color coordinates matching the display requirements (<0.1). The strategy is to combine weak spiro‐donor and spiro‐acceptor groups into a linear donor‐π‐acceptor type of thermally‐activated delayed fluorescence molecule through a sterically bulky π‐spacer. The strategy endows an emitter with deep‐blue emission, a narrower emission bandwidth (51 nm in toluene), a high photoluminescence quantum yield (0.95 in toluene), weak concentration quenching, and efficient triplet‐exciton utilization, which are all attractive characteristics for emitters of deep‐blue OLEDs with lower CIEy coordinates. Owing to the rational design, the emitter has realized not only highly efficient doped deep‐blue OLEDs with external quantum efficiencies (EQEs) up to 25.4 % and CIEy less than 0.1 but also so far the most efficient nondoped deep‐blue OLED (EQE up to 22.5 %) with CIEy less than 0.1.
Nowadays, thermally activated delayed
fluorescence (TADF) compounds
with a fused-ring core skeleton are getting increasing research interest
because of their use in high-performance organic light-emitting diodes
(OLEDs). In this study, TADF compounds featuring a D–A-type
fused-ring core skeleton are developed. The challenging compatibility
of a planarized D–A arrangement and the TADF property is achieved
through linking the D and A moieties with two oxygen atoms within
a six-membered ring. Compared with a single-oxygen analogue possessing
a flexible skeleton and a twisted D–A arrangement, these fused-ring
compounds with higher skeleton rigidity show higher photoluminescence
quantum yields and narrower emission spectra in toluene and in doped
thin films. Their electroluminescent devices achieve high external
quantum efficiencies (up to 19.4%), suggesting the potential of rarely
achieved D–A-type fused-ring TADF systems to serve as high-performance
emitters of OLEDs.
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