Intramolecular‐Locked High Efficiency Ultrapure Violet‐Blue (CIE‐y <0.046) Thermally Activated Delayed Fluorescence Emitters Exhibiting Amplified Spontaneous Emission

Abstract

Rational manipulation of frontier orbital distribution and singlet‐triplet splitting is crucial to exploit the luminescent properties of organic molecules. To realize ultra‐blue luminescence, both blue‐shifted wavelength peak (λpeak) and narrow full‐width at half‐maximum (FWHM) are required. Herein, a new thermally activated delayed fluorescence (TADF) skeleton by inserting the diphenyl methylene intramolecular‐lock to adjust the torsion angles and restrict the intramolecular relaxation is developed. Two rigid emitters, incorporating phenoxazine (PXZN‐B) and acridine (DMACN‐B) as donors and mesitylboron as an acceptor, exhibit narrow FWHMs (<50 nm) with deep‐blue (0.133, 0.147) and violet‐blue emission (0.151, 0.045), respectively. In particular, the Commission Internationale de l'Eclairage (CIE) coordinates of a DMACN‐B‐based device closely approach the Rec.2020 standard (0.131, 0.046). Moreover, both of the organic light‐emitting diodes (OLEDs) based on PXZN‐B and DMACN‐B show TADF character, with high external quantum efficiencies (EQEs) exceeding 10%. Furthermore, owing to the large orbital overlap, these TADF emitters own a fast S1–S0 transition rate exceeding 108 s–1, thereby exhibiting marked amplified spontaneous emission (ASE) with low thresholds. Therefore, the intramolecular‐lock strategy provides not only innovation for realizing high‐efficiency deep‐blue TADF emission with high color purity but also an avenue for a TADF‐based ASE and lasing application.

2,6‐Dicarbonitrile Diphenyl‐1λ5‐Phosphinine (DCNP)—A Robust Conjugated Building Block for Multi‐Functional Dyes Exhibiting Tunable Amplified Spontaneous Emission

“…Therefore, up to now, very limited TADF materials with unconventional molecular structures can exhibit amplified spontaneous emission (ASE) properties. [12,33,34] However, from the aspect of color tuning in CT emission, wide-range color-shifting from violet-blue to NIR has been realized through manipulating the relative D-A strength. [35] Moreover, the treatment of triplets is crucial for organic lasing activity.…”

Isomeric thermally activated delayed fluorescence emitters based on a quinolino[3,2,1-de]acridine-5,9-dione multiple resonance core and carbazole substituent

“…And we further judged the color purity of the three molecules using the range-separated hybrid (RSH) functions previously proposed by our group. 47 Based on the calculation equation, the RSHs of D1, D2, and D3 were calculated to be 1.98, 1.96, and 1.98, respectively, which are all close to 1.7, further illustrating that these devices all exhibit good color purity (Table S7, ESI†). The maximum EQE (EQE max ) of D1 could reach 16.9%.…”

Deep‐Blue OLEDs with Rec.2020 Blue Gamut Compliance and EQE Over 22% Achieved by Conformation Engineering

“…Among the three primaries (red, green, and blue), researchers devote extensive endeavors in pursuing blue emitters satisfying the Rec.2020 standard, that is, Commission Internationale de l'Éclairage (CIE) chromaticity coordinates of (0.131, 0.046), [ 5 ] as the blue primary can simultaneously widen color gamut and reduce the power consumption of the display. [ 6–8 ]…”