Thermally activated delayed fluorescence enantiomers for solution-processed circularly polarized electroluminescence

Abstract

Circularly polarized organic light-emitting diodes (CP-OLEDs) with thermally activated delayed fluorescence (TADF) characteristics are receiving increasing interest, as they have shown improving efficiencies of circularly polarized electroluminescence (CPEL). Here, we developed a series of TADF enantiomers based on chiral binaphthalene, an acceptor (A) of cyanopyridine, and donors (D) of carbazoles in a chiral–A–D architecture. Good solubility, high luminescence yields, and excellent chiral stability with a photoluminescence dissymmetry factor (g_PL) up to 5.8 × 10⁻⁴ were achieved. Efficient CP-OLEDs using these chiral TADF molecules as dopants were successfully fabricated, exhibiting high external quantum efficiencies (EQEs) up to 12.4% and opposite CPEL signals with g_EL of 6 × 10⁻⁴/−8.6 × 10⁻⁴ in vacuum-deposited devices. More impressively, the solution-processed TADF CP-OLEDs result in much larger g_EL values (3.5 × 10⁻³/−3.9 × 10⁻³) with EQEs up to 10.6%. This discovery is encouraging and instructive, which could stimulate the development of high-performance CP-OLEDs using chiral TADF molecules through solution-processing approaches.