Chiral Octahydro-Binaphthol Compound-Based Thermally Activated Delayed Fluorescence Materials for Circularly Polarized Electroluminescence with Superior EQE of 32.6% and Extremely Low Efficiency Roll-Off

Abstract

Circularly polarized organic light-emitting diodes (CP-OLEDs) are particularly favorable for the direct generation of CP light, and they demonstrate a promising application in 3D display. However, up to now, such CP devices have suffered from low brightness, insufficient efficiency, and serious efficiency roll-off. In this study, a pair of octahydro-binaphthol (OBN)-based chiral emitting enantiomers, (R/S)-OBN-Cz, are developed by ingeniously merging a chiral source and a luminophore skeleton. These chirality-acceptor-donor (C-A-D)-type and rod-like compounds concurrently generate thermally activated delayed fluorescence with a small ΔE_ST of 0.037 eV, as well as a high photoluminescence quantum yield of 92% and intense circularly polarized photoluminescence with dissymmetry factors (|g_PL |) of ≈2.0 × 10^-3 in thin films. The CP-OLEDs based on (R/S)-OBN-Cz enantiomers not only display obvious circularly polarized electroluminescence signals with a |g_EL | of ≈2.0 × 10^-3 , but also exhibit superior efficiencies with maximum external quantum efficiency (EQE_max ) up to 32.6% and extremely low efficiency roll-off with an EQE of 30.6% at 5000 cd m^-2 , which are the best performances among the reported CP devices to date.

Keywords: chiral octahydro-binaphthol compound; circularly polarized organic light-emitting diodes; high efficiency; low efficiency roll-off; thermally activated delayed fluorescence.