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Near‐infrared exciplex can weaken molecular design difficulties, and has the advantage of easy bathochromic‐shift spectra via selecting the suitable electron donors and acceptors. In this contribution, exciplex is applied to fabricate near‐infrared (NIR) organic light‐emitting diodes (OLEDs) incorporating a synthesized fluorescent material 3‐([1,1″:3′,1″‐terphenyl]‐5′‐yl)acenaphtho[1,2‐b]pyrazine‐8,9‐dicarbonitrile (APDC‐tPh) and a commercially available material 4,4′,4″‐tris(carbazol‐9‐yl)triphenylamine (TCTA). The device having a mixed TCTA:APDC‐tPh as an emitting layer shows a 730 nm NIR emission with a maximum external quantum efficiency (EQE) of about 0.1%, while the device having 2‐[4‐(diphenylamino)phenyl]‐10,10‐dioxide‐9H‐thioxanthen‐9‐one (TXO‐TPA):APDC‐tPh as the emitting layer exhibits an emission peak of 704 nm with a maximum EQE of 1.27%. These results prove the feasibility of fabricating the efficient exciplex‐based NIR OLEDs. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Multiple resonances induced thermally activated delayed fluorescence (MR‐TADF) has great advantages in high color purity display. Up to now, current MR‐TADF emitters are only based on the boron‐nitrogen‐containing fragment. Reported herein is a novel class of MR‐TADF emitter, quinolino[3,2,1‐de]acridine‐5,9‐dione (QAO), realized by the opposite resonance effect of the carbonyl and the nitrogen atoms, which is also the smallest TADF emitter reported so far. The QAO‐based pure blue organic light‐emitting diode achieves a maximum external quantum efficiency (EQEmax) of 19.4% with a small full width at half maximum of 39 nm. Moreover, tert‐butyl modified QAO can be employed as an efficient electron acceptor to construct an efficient yellow‐green evaporation and solution process feasible TADF emitter, 7‐(tert‐butyl)‐3,11‐bis(9,9‐dimethylacridin‐10(9H)‐yl)quinolino[3,2,1‐de]acridine‐5,9‐dione (QAO‐DAd), with significantly improved performance as compared to the previous flexible diketone‐based emitters. A novel class of multiple resonance induced thermally activated delayed fluorescence (MR‐TADF) emitter (QAO) is developed, by using the opposite resonance effect of the carbonyl group and the nitrogen atom. Moreover, QAO can be employed as an efficient electron acceptor to construct traditional donor–acceptor–donor type TADF emitter, QAO‐DAd, and then achieve high performances in evaporation and solution‐processed devices. [ABSTRACT FROM AUTHOR]