Planar Chiral Copper(I) Complexes Realize Efficient Circularly Polarized Electroluminescence

Chiral organometallic emitters hold great promise in potential and practical applications of circularly polarized organic light-emitting diodes (CP-OLEDs). However, developing luminescent earth-abundant organometallic complexes concurrently exhibiting circularly polarized luminescence (CPL) and high quantum efficiency remain a formidable challenge. In this study, we introduced a typical planar chiral skeleton of a [2.2]paracyclophane moiety into earth-abundant copper(I) complexes with the goals of realizing efficient CPL and thermally activated delayed fluorescence (TADF) simultaneously. Two pairs of proof-of-the-concept copper(I) enantiomers, Rp/Sp-MAC*-Cu-CzP and Rp/Sp-MAC*-Cu-CNCzP, were developed using planar chiral [2.2]paracyclophane-based donor ligands in a carbene-metal-amide (CMA) motif. Both panels of enantiomers not only exhibited significant mirror-image CPL signals but also displayed distinct TADF nature with fast reverse intersystem crossing rates of up to 108 s−1. The resultant OLEDs based on the MAC*-Cu-CzP enantiomers manifested efficient circularly polarized electroluminescence with excellent external quantum efficiencies of 13.2% with ultraslow efficiency roll-off (7.7% at 10000 nits). This work not only demonstrates one of the best performance for CP-OLEDs based on earth-abundant organometallic complexes but also represents the first example of CP-OLEDs from CMA complexes to our knowledge.