Donor–Acceptor Molecules with Locked sp3 Carbon Link for Highly Efficient Near Ultraviolet Organic Light‐Emitting Diodes

Abstract To achieve high‐performance near ultraviolet (NUV) organic light‐emitting diodes (OLEDs), highly stable and fluorescent emitters with good triplet utility are essential. The challenge in making such molecules stems from the fact that a wide bandgap and strong luminescence are two conflicting requirements. Herein, a new strategy is proposed for NUV emitters featuring donor–acceptor moieties linked by a rigid sp 3 carbon atom to weaken the conjugation and reduce nonradiative processes. The resultant emitters exhibit excellent NUV luminescence, high thermal and electrochemical stabilities, and hybridized local and charge‐transfer excited‐state characteristics. A nondoped device emits NUV light (414 nm, Commission Internationale de L'eclairage coordinates [CIE x , y ] = 0.157, 0.058) with a maximum luminance, current efficiency, and external quantum efficiency (EQE) of 7979 cd m −2 , 2.53 cd A −1 , and 6.60%, respectively. The device also shows a small efficiency roll‐off of 6.8% at 1000 cd m −2 . A doped device acquires a high efficiency and color purity with a maximum EQE of 7.64%, CIE x , y of (0.158, 0.049), and emission peak of 406 nm, representing one of the best values among NUV OLEDs. This research provides an effective method to achieve high‐performance NUV OLEDs and also offers flexibility in material design.