Solution‐Processable Pure‐Red Multiple Resonance‐induced Thermally Activated Delayed Fluorescence Emitter for Organic Light‐Emitting Diode with External Quantum Efficiency over 20 %

Abstract

Developing solution-processable red organic light-emitting diodes (OLEDs) with high color purity and efficiency based on multiple resonance thermally activated delayed fluorescence (MR-TADF) is a formidable challenge. Herein, by introducing auxiliary electron donor and acceptor moieties into the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) distributed positions of multiple resonance skeleton simultaneously, an effective strategy to obtain red MR-TADF emitters was represented. The proof-of-the-concept molecule BN-R exhibits a narrowband pure-red emission at 624 nm, with a high luminous efficiency of 94 % and a narrow bandwidth of 46 nm. Notably, the fabricated solutionprocessable pure-red OLED based on BN-R exhibits a state-of-the-art external quantum efficiency over 20 % with the Commission Internationale de I'Éclairage coordinates of (0.663, 0.337) and a long operational lifetime (LT 50 ) of 1088 hours at an initial luminance of 1000 cd m À 2 .

Solution-processed orange and white OLEDs sensitized by an electroactive pure organic room-temperature phosphorescent polymer

“…We note that it is based on vacuum thermal deposition, and there are few reports about solutionprocessed PSF, which is believed to be more compatible with low-cost, large area and flexible displays in the future. [22][23][24][25] In addition, solution-processed white OLEDs adopt a straightforward single-emissive-layer structure that incorporates various functional materials, including a host material combined with blue/yellow or blue/green/red emitters. These emitters that encompass all-phosphorescent, 26 TADF/phosphorescent hybrid [27][28][29][30] and all-TADF white OLEDs [31][32][33][34] have the capability to efficiently harness excitons, thus achieving 100% IQE.…”

“…We note that it is based on vacuum thermal deposition, and there are few reports about solution-processed PSF, which is believed to be more compatible with low-cost, large area and flexible displays in the future. 22–25…”

Spirofluorene-locked carbazole based multiple resonance thermally activated delayed fluorescence emitters for efficient solution-processed narrowband green OLEDs

“…37 However, it should be noted that the majority of present MR-TADF-based OLEDs were fabricated by vacuum deposition, while the development of solution-processed MR-TADF emitters suitable for the fabrication of low-cost and large-area OLEDs has lagged behind and is still to be addressed. [38][39][40][41][42][43] Here, we report the design, synthesis and properties of two novel MR-TADF emitters (SpDCz and DSpDCz, Fig. 1) consisting of spirofluorene-locked carbazole moieties in the periphery of a boron, nitrogen-doped polycyclic aromatic hydrocarbon (BNN) skeleton, which can be used for the fabrication of solutionprocessed green-emitting narrowband OLEDs.…”

Precise modulation of multiple resonance emitters toward efficient electroluminescence with pure-red gamut for high-definition displays

“…Despite numerous reports on high-performance emitters based on the MR strategy, only a scant few of these materials produce red emissions due to the nonbonding nature of the MR skeleton, which limits their conjugation even with expanded planar structures ( 32 – 38 ). A feasible alternative for achieving red-shifted emissions is to increase the CT character via peripheral decoration; however, this approach typically weakens the MR effect and broadens the emission spectra ( 37 , 39 – 41 ). To surmount this challenge, researchers have boosted the donating/accepting strengths of MR emitters by integrating para B-π-B and N-π-N units in a central phenyl ring ( 32 ).…”