Highly stable and efficient copper(I) sensitizer for narrowband red organic light-emitting diodes with an operational lifetime (LT95) of up to 3689 h at 1000 cd m−2

Copper-based organic light-emitting diodes (OLEDs) are low-cost alternatives to precious metal-based OLEDs, but currently no such OLEDs can meet the practical requirements for high colour purity, device efficiency, and operational stability. Carbene-Cu(I)-amide emitters reported here exhibited thermally activated delayed fluorescent emission with quantum efficiencies up to 0.90 and radiative decay rates of 2.7 × 10⁶ s^-1. These enable blue to near-infrared Cu(I)-OLEDs with high brightness (265,000 cd m^-2) and extended LT₉₅ lifetime (3582 hours at 1000 cd m^-2). Deuteriation and π-extension of carbazole significantly enhance OLED stability. Cu(I)-sensitized fluorescence OLEDs showed efficient narrowband electroluminescence (λ_max 612-614 nm; full-width half maximum of 33-38 nm; maximum external quantum efficiencies reach 21.9%) and prolonged LT₉₅ lifetime (up to 3689 h at 1000 cd m^-2). This work highlights earth-abundant metal-based sensitized-OLEDs that exhibit high colour purity and long device lifetime comparable to the best non-iridium metal-based OLEDs.