Simple Double Hetero[5]helicenes Realize Highly Efficient and Narrowband Circularly Polarized Organic Light-Emitting Diodes

Helicene-based emitters with unique inherent circularly polarized luminescence (CPL) are promising yet remain a formidable challenge for highly efficient circularly polarized organic light-emitting diodes (CP-OLEDs), ascribed to their tough synthesis, low emission efficiency, and easy racemization in the thermal deposition process. Herein, a pair of helicene-based enantiomers, namely (P)-helicene-BN and (M)-helicene-BN, were developed, which merge helical chirality and the B/N/S inserted polycyclic aromatic framework to concurrently feature CPL and narrow thermally activated delayed fluorescence (TADF) characteristics. Benefiting from the excellent thermal/photophysical/chiroptical properties, the narrowband green CP-OLEDs based on enantiomers achieved maximum external quantum efficiencies (EQE(max)) of up to 31.5%, and dissymmetry factor (|g(EL)|) of 2.2 x 10(-3). This work reveals the great potential of helicene-based emitters in CP-OLEDs.