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 lightemitting 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-theconcept 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-Cz P 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.

Luminescent gold(Ⅲ)exciplexes enable efficient multicolor electroluminescence

The control of excited states and related emissive properties of gold(Ⅲ)complexes mainly depends on the modulation of intramolecular electronic interactions among gold(Ⅲ)metal center,chelating ligands and/or peripheral groups.However,luminescent gold(Ⅲ)systems based on intermolecular electronic interactions have never been explored.Here we report a series of proof-of-concept gold(Ⅲ)exciplexes using a simple gold(Ⅲ)complex,AuDPPy,as an electron acceptor.The emissive properties of gold(Ⅲ)exciplexes can be regulated by combining AuDPPy with different donors.Inspiringly,these gold(Ⅲ)exciplexes have donor-dependent emission mechanisms:dominant phosphorescence or dual radiative channels of thermally activated delayed fluorescence(TADF)and phosphorescence.Consequently,these gold(Ⅲ)exciplexes deliver green-to-red electroluminescence with external quantum efficiencies(EQEs)of up to 10.1%.More importantly,using these gold(Ⅲ)exciplexes to host multi-resonance TADF emitters results in narrowband yellow,orange,and deep-red electroluminescence with high EQEs of 23.5%,24.4%,and 27.4%,respectively,competitive to the highest values for gold(Ⅲ)OLEDs in similar color gamut.

Multiple Resonance Thermally Activated Delayed Fluorescence Sensitizers Enable Green-toUltraviolet Photon Upconversion:Application in Photochemical Transformations

Efficient visible-to-ultraviolet(UV)triplet-triplet annihilation upconversion(TTA-UC)with large anti-Stokes shift is highly promising for solar-powered and indoor applications.Nonetheless,the excitationwavelengthis confined to the blue region(<450 nm),mainly due to large energy loss during triplet sensitization,resulting in reduced photon utilization efficiency in practical scenarios.Herein,a series of multiple resonance thermally activated delayed fluorescence(MR-TADF)compounds are developed as purely organic sensitizers for the purpose of energy-loss reduction,which also feature intense absorbance in the visible region,high intersystem crossing efficiencies,and long triplet lifetimes.By pairing the MR-TADF sensitizers with appropriate acceptors,green-to-UV TTA-UC systems were realized with an anti-Stokes shift up to 1.05 eV,upconversion quantum yield up to 8.6%,and threshold excitation intensity as low as 9.2 mW cm^(−2) in solution.The TTA-UC pairs were applied as internal or external sources of UV photons to trigger energy-demanding photopolymerization and photoligation reactions even under excitation of low-power-density green light-emitting diode light,revealing the broad utility of thesemolecular upconverters.This work unlocks the huge potential of MR-TADF-type sensitizers in upconversion applications.