Side by Side Alignment of Donors Enabling High‐Efficiency TADF OLEDs with Insensitivity to Doping Concentration

Abstract Doping sensitivity is a great obstacle in boosting thermally activated delayed fluorescence (TADF)‐based organic light‐emitting diodes into practical application. Herein, a “side by side” donor alignment strategy is proposed to achieve decent electroluminescence performance under high doping concentration by studying the structure–property relationship of two emitters D2T‐TRZ and D2Y‐TRZ. D2T‐TRZ containing parallel aligned donors shows high photoluminescent quantum yield (PLQY) and short delayed lifetime (τ_d) in both doped and neat films, which endow its excellent performances with maximum external quantum efficiencies (EQE_maxs) higher than 22% under wide doping range of 10–70 wt%. While, composed of antiparallel acridans, D2Y‐TRZ presents good PLQY and relatively long τ_d when diluted in host matrix, but undergoes severe quenching in neat films. Consequently, D2Y‐TRZ achieves lower EQE_maxs of 14.9–16.4% within narrow range of 10–40 wt%. This result reveals parallel aligned donors as a better choice to design TADF emitters inert to doping concentration.