An A‐D‐A‐Type Thermally Activated Delayed Fluorescence Emitter with Intrinsic Yellow Emission Realizing Record‐High Red/NIR OLEDs upon Modulating Intermolecular Aggregations

Abstract Realizing efficient red/near‐infrared (NIR) electroluminescence (EL) by precisely modulating molecular aggregations of thermally activated delayed fluorescence (TADF) emitters is an attractive pathway, yet the molecular designs are elusive. Here, a new approach is proposed to manage molecular aggregation via a mild‐twist acceptor‐donor‐acceptor (A‐D‐A)‐type molecular design. A proof‐of‐concept TADF molecule, QCN‐PhSAC‐QCN , is developed that furnishes a fast radiative rate and obvious aggregation‐induced emission feature. Its emission bands can be facilely shifted from intrinsic yellow to the red/NIR region via fine‐tuning doping levels and molecular aggregates while maintaining elegant photoluminescence quantum yields benefiting from suppressed exciton annihilation processes. As a result, a QCN‐PhSAC‐QCN ‐based organic light‐emitting diode (OLED) exhibits a record‐setting external quantum efficiency (EQE) of 39.1% at a doping ratio of 10 wt.%, peaking at 620 nm. Moreover, its nondoped NIR OLED affords a champion EQE of 14.3% at 711 nm and retains outstanding EQEs of 5.40% and 2.35% at current densities of 10 and 100 mA cm −2 , respectively, which are the highest values among all NIR‐TADF OLEDs at similar density levels. This work validates the feasibility of such mild‐twist A‐D‐A‐type molecular design for precisely controlling molecular aggregation while maintaining high efficiency, thus providing a promising pathway for high‐performance red/NIR TADF OLEDs.