Precisely regulating the double-boron-based multi-resonance framework towards pure-red emitters: high-performance OLEDs with CIE coordinates fully satisfying the BT. 2020 standard

Abstract

Here, we propose a new simple and effective strategy for designing pure-red multi-resonance (MR) emitters through precisely regulating the double-boron-based MR framework. The designed two emitters exhibit ultrapure red emission...

Boron-containing helicenes as new generation of chiral materials: opportunities and challenges of leaving the flatland

“…5) resulted in the red emitters containing one [7]-and one [5] helicene moiety. 178 When embedded in a host matrix (1 wt%) together with a sensitizer, they produced EL devices with l EL of 632 and 645 nm, corresponding to the CIE coordinates of (0.689, 0.311) and (0.701, 0.301), and excellent EQE max of 33.1 and 34.7%. Remarkably, the sensitized OLEDs constructed with 2 wt% 140 achieved the optimal coordinates (0.708, 0.292) according to the BT.2020 standard, although its EQE decreased with the increase of the 140 concertation in EML.…”

Marching Toward Long‐Wavelength Narrowband Emissive Multi‐Resonance Delayed Fluorescence Emitters for Organic Light Emitting Diodes

“…[141] 4) Another interesting strategy is metal-perturbation into the MR-core; by introducing metals such as Au and Pt, the SOC for the ISC and RISC significantly improved; [142][143][144] which is one of the feasible solution to boost the RISC of MR-TADF emitters without compromising color purity; 5) From device engineering point of view, employing the MR-emitter as terminal dopant in sensitized device structure is advantageous for suppressing the triplet exciton quenching, leading to the reduced efficiency roll-off and improved operation stability. [90][91][92] For improving the RISC of longwavelength emitters with high color purity, we believe that the integration of multiple design strategies such as para-N-𝜋-N and para-B-𝜋-B, heavy atom incorporation and 𝜋-extension together in one molecular design is ideal.…”

“…developed a series of pure red‐MR TADF emitters by replacing the one of the para ‐N‐π‐N with para ‐O‐π‐O resulted BNO1‐BNO3 . [ 91 ] The emission wavelengths and TADF features of the materials were modulated by peripheral decoration of aryl units on O‐atom ( Figure ). The optical properties of these materials are hypochromic shifted compared to the R‐TBN because of the reduced electron donating strength of O than N. Nonetheless, all the materials displayed λ PL > 600 nm and narrow FWHM < 33 nm.…”

“…However, due to the atomically separated HOMO and LUMO orbitals, the MR‐TADF emitters possess feeble CT character, hence it is highly challenging to realize bathochromic shifted emission from blue‐green region. [ 51–149 ] However, the long‐wavelength ( λ em > 550 nm) MR‐TADF emitters with narrow FWHM are scarcely reported due to the limited scope for structural diversity, weak short range charger transfer (SRCT) and complicated synthetic procedures. [ 85–113 ] Therefore, it is urgent need to develop new emitter designs for constructing long‐wavelength MR‐TADF emitters without compromising the FWHM.…”

“…[ 51–149 ] However, the long‐wavelength ( λ em > 550 nm) MR‐TADF emitters with narrow FWHM are scarcely reported due to the limited scope for structural diversity, weak short range charger transfer (SRCT) and complicated synthetic procedures. [ 85–113 ] Therefore, it is urgent need to develop new emitter designs for constructing long‐wavelength MR‐TADF emitters without compromising the FWHM. Besides, although the conceptual advancement has been derived several MR‐TADF emitters, contrary to the conventional TADF emitters, they often possess low spin up conversion rates ( k RISC ≈ 10 4 s −1 ), which leads to the undesirable bimolecular quenching and severe efficiency roll‐off at practical brightness; this needs to be resolved from material design perspective.…”