Excited‐State Engineering Enables Efficient Deep‐Blue Light‐Emitting Diodes Exhibiting BT.2020 Color Gamut

• Published in: Advanced materials (Weinheim) 2024-08, Vol.36 (31), p.e2313602-n/a
• Main Authors: An, Rui‐Zhi, Sun, Yuqi, Chen, Hao‐Yang, Liu, Yuan, Privitera, Alberto, Myers, William K., Ronson, Tanya K., Gillett, Alexander J., Greenham, Neil C., Cui, Lin‐Song
• Format: Article
• Language: English
• Subjects: bt.2020; deep‐blue emission; Emitters; Excitons; Fluorescence; High definition; hybrid long‐/ short‐range charge‐transfer; Organic light emitting diodes; Quantum efficiency; thermally activated delayed fluorescence
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202313602

Organic luminescent materials that exhibit thermally activated delayed fluorescence (TADF) can convert non‐emissive triplet excitons into emissive singlet states through a reverse intersystem crossing (RISC) process. Therefore, they have tremendous potential for applications in organic light‐emitting diodes (OLEDs). However, with the development of ultra‐high definition 4K/8K display technologies, designing efficient deep‐blue TADF materials to achieve the Commission Internationale de l’Éclairage (CIE) coordinates fulfilling BT.2020 remains a significant challenge. Here, an effective approach is proposed to design deep‐blue TADF molecules based on hybrid long‐ and short‐range charge‐transfer by incorporation of multiple donor moieties into organoboron multiple resonance acceptors. The resulting TADF molecule exhibits deep‐blue emission at 414 nm with a full width at half maximum (FWHM) of 29 nm, together with a thousand‐fold increase in RISC rate. OLEDs based on the champion material achieve a record maximum external quantum efficiency (EQE) of 22.8% with CIE coordinates of (0.163, 0.046), approaching the coordinates of the BT.2020 blue standard. Moreover, TADF‐assisted fluorescence devices employing the designed material as a sensitizer exhibit an exceptional EQE of 33.1%. This work thus provides a blueprint for future development of efficient deep‐blue TADF emitters, representing an important milestone towards meeting the blue color gamut standard of BT.2020. Here, an effective approach is proposed to design deep‐blue thermally activated delayed fluorescence molecules based on hybrid long‐ and short‐range charge‐transfer by incorporating multiple donor moieties into organoboron multiple resonance acceptors. The resulting molecule exhibits deep‐blue emission, narrow spectra, and high reverse intersystem crossing rate. The organic light‐emitting diode fabricated with the designed molecule records maximum external quantum efficiency of 22.8% with the Commission Internationale de l’Éclairage coordinates of (0.163, 0.046).