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

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 (tau(d)) in both doped and neat films, which endow its excellent performances with maximum external quantum efficiencies (EQE(max)s) higher than 22% under wide doping range of 10-70 wt%. While, composed of antiparallel acridans, D2Y-TRZ presents good PLQY and relatively long tau(d) when diluted in host matrix, but undergoes severe quenching in neat films. Consequently, D2Y-TRZ achieves lower EQE(max)s 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.

Automated summary

This study proposes a side by side donor alignment strategy to achieve decent electroluminescence performance under high doping concentration, by investigating the structure-property relationship of two emitters D2T-TRZ and D2Y-TRZ. The results reveal that TADF emitters with parallel aligned donors, such as D2T-TRZ, show higher efficiency and are less sensitive to doping concentration compared to those with antiparallel acridans like D2Y-TRZ.