No abstract

basically limited to donor (D)-π-acceptor (A) molecular architecture. [2] This type of molecular design, first proposed by Adachi and co-workers for TADF, [1a] can tune their D or/and A groups, geometries, and steric hindrance between them to generate twisted induced charge-transfer-type emission. [3] The twisted dihedral angle between D and A units can minimize the singlettriplet splitting energy (ΔE ST) for fast RISC, [1c,4] but the resulted TADF OLEDs still need to be significantly improved, notably in terms of efficiency roll-off at high brightness and concentration quenching because of the ππ intermolecular interactions in the solid-state. [5] Another way to achieve TADF is to use D/A complex, in which the D/A blocks are spatially isolated, but their forming exciplexes are far less efficient than D-π-A analogs, and the resulting OLEDs also display severe efficiency roll-off. [6] Recently, researchers conceptually consider that the intramolecular noncovalent interaction between D/A units in faceto-face alignment could be a new option to realize TADF. [7] Constructing TADF materials in this unconjugated way has the potential to combine the small ΔE ST value with substantial transition dipole and achieve high luminescent efficiency. [8] These two electron-rich and electron-poor π-systems need to be held close in space to form homoconjugation. In this regard, The ORCID identification number(s) for the author(s) of this article can be found under

Near-infrared (NIR) organic solid-state lasers play an essential role in applications ranging from laser communication to infrared night vision, but progress in this area is restricted by the lack of effective excited-state gain processes. Herein, we originally proposed and demonstrated the cascaded occurrence of excited-state intramolecular proton transfer for constructing the completely new energy-level systems.Cascading by the first ultrafast proton transfer of < 430 fs and the subsequent irreversible second proton transfer of ca. 1.6 ps,the stepwise proton transfer process favors the true six-level photophysical cycle,w hichs upports efficient population inversion and thus NIR single-mode lasing at 854 nm. This work realizes longest wavelength beyond 850 nm of organic single-crystal lasing to date and originally exploits the cascaded excited-state molecular proton transfer energy-level systems for organic solid-state lasers.

Organic materials with violet electroluminescence are highly interesting for organic light‐emitting diode (OLED) application. However, the design and synthesis of new molecules combining with desirable violet emission and high luminous efficiency are a challenging task. Here, three novel organic molecules consisting of a pyrene unit and a highly rigid skeleton, namely TFPy2, TFPy3, and TFPy4, are developed for violet‐emitting OLEDs (VOLEDs). These emitters exhibit excellent thermal stability and violet emission with a narrow full width at half‐maximum (FWHM) and high photoluminescence quantum yields (PLQYs). Photophysical results show that the emission peaks can be tuned by the introduction of pyrene units at different positions, and the emission will have a blue shift with increasing steric hindrance. Moreover, OLEDs fabricated with TFPy2, TFPy3, and TFPy4 as the emitters exhibit maximum external quantum efficiencies (EQEs), emission peaks, and CIEs (x,y) of 3.8%, 414 nm, and (0.15, 0.03); 4.8%, 406 nm, and (0.16, 0.02); and 5.1%, 404 nm, and (0.16, 0.02), respectively. The two molecules TFPy3 and TFPy4 exhibit violet emissions with EL peaks at ≈405 nm with a record low CIEy of 0.02. Therefore, these materials and their construction strategy are promising for future VOLEDs with wide‐color‐gamut display and potential biological applications.

No abstract

A narrowband blue CP-TADF emitter with a rigid hetero-helicene structure (QAO-PhCz) was synthesized and characterized. QAO-PhCz exhibits good electroluminescence performance (EQE = 14.0%) and narrow FWHM. The enantiomers of QAO-PhCz...

Intramolecular spatial charge transfer (ISCT) plays a critical role in determining the optical and charge transport properties of thermally activated delayed fluorescence (TADF) materials. Herein, a new donor/acceptor-type TADF compound based on rigid dibenzothiophene sulfone (DBTS) moiety, STF-DBTS, was designed and synthesized. Fluorene unit was used as a rigid linker to position the rigid acceptor and donor subunit in close vicinity with control over their spacing and molecular structure and to achieve high photoluminescence quantum yield (∼53%) and TADF property. For comparison purposes, we constructed the more flexible STF-DPS with a less rotationally constrained diphenylsulphone (DPS) acceptor instead of the rigid DBTS units, and STF-DPS showed no TADF properties and lower PLQY (16.0%). Organic light-emitting diodes (OLEDs) based on STF-DBTS achieve an external quantum efficiency (EQE) of 10.3% at 488 nm, which is a fivefold improvement in EQE with respect to STF-DPS.

A hetero-bichromophore thermally activated delayed fluorescence (TADF) emitter named BOQAO was designed and synthesized, which consists of two multi-resonance TADF (MR-TADF) core tBuBO and tBuQAO. The short-range intramolecular charge transfer...