Planar Chiral Multiple Resonance Thermally Activated Delayed Fluorescence Materials for Efficient Circularly Polarized Electroluminescence

Chiral boron/nitrogen doped multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters are promising for highly efficient and color‐pure circularly polarized organic light‐emitting diodes (CP‐OLEDs). Herein, we report two pairs of MR‐TADF materials (Czp‐tBuCzB, Czp‐POAB) based on planar chiral paracyclophane with photoluminescence quantum yields of up to 98 %. The enantiomers showed symmetric circularly polarized photoluminescence spectra with dissymmetry factors |gPL| of up to 1.6×10−3 in doped films. Meanwhile, the sky‐blue CP‐OLEDs with (R/S)‐Czp‐tBuCzB showed an external quantum efficiency of 32.1 % with the narrowest full‐width at half‐maximum of 24 nm among the reported CP‐OLEDs, while the devices with (R/S)‐Czp‐POAB displayed the first nearly pure green CP electroluminescence with |gEL| factors at the 10−3 level. These results demonstrate the incorporation of planar chirality into MR‐TADF emitter is a reliable strategy for constructing of efficient CP‐OLEDs. Two efficient planar chiral multiple resonance thermally activated delayed fluorescent compounds showing narrow emissions and circularly polarized luminescence were prepared. The sky‐blue circularly polarized organic light‐emitting diode exhibited the narrowest emission and high external quantum efficiency of 32.1 %, and the first nearly pure green circularly polarized electroluminescence was realized. Both devices display g factors at 10−3 level.