Copper(I) complexes with planar chirality 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 remains 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 goal of realizing efficient CPL and thermally activated delayed fluorescence (TADF) simultaneously. Two pairs of proof-of-the-concept copper(I) enantiomers, R-p/S-p-MAC*-Cu-CzP and R-p/S-p-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 10(8) 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% and ultraslow efficiency roll-off (7.7% at 10,000 nits). This article not only demonstrates one of the best performances for CP-OLEDs based on earth-abundant organometallic complexes but also represents the first example of CP-OLEDs from CMA complexes to our knowledge.

Automated summary

This study successfully achieved efficient circularly polarized luminescence and thermally activated delayed fluorescence by introducing a typical planar chiral skeleton [2.2]paracyclophane into earth-abundant copper(I) complexes. Two pairs of proof-of-the-concept copper(I) enantiomers were developed, which not only exhibited significant mirror-image CPL signals but also displayed distinct TADF nature. The resultant OLEDs manifested efficient circularly polarized electroluminescence with excellent external quantum efficiencies, representing one of the best performances for CP-OLEDs based on earth-abundant organometallic complexes and the first example of CP-OLEDs from CMA complexes to our knowledge.