Highly Efficient Electroluminescence from Narrowband Green Circularly Polarized Multiple Resonance Thermally Activated Delayed Fluorescence Enantiomers

Abstract

Purely organic fluorescent materials that concurrently exhibit high efficiency, narrowband emission, and circularly polarized luminescence (CPL) remain an unaddressed issue despite their promising applications in wide color gamut- and 3D-display. Herein, the CPL optical property and multiple resonance (MR) effect induced thermally activated delayed fluorescence (MR-TADF) emission are integrated with high color purity and luminous efficiency together. Two pairs of highly efficient green CP-MR-TADF enantiomers, namely, (R/S)-OBN-2CN-BN and (R/S)-OBN-4CN-BN, are developed. The enantiomer-based organic light-emitting diodes (OLEDs) exhibit pure green emission with narrow full-width at half-maximums (FWHMs) of 30 and 33 nm, high maximum external quantum efficiencies (EQEs) of 29.4% and 24.5%, and clear circularly polarized electroluminescence (CPEL) signals with electroluminescence dissymmetry factors (g_EL ) of +1.43 × 10^-3 /-1.27 × 10^-3 and +4.60 × 10^-4 /-4.76 × 10^-4 , respectively. This is the first example of a highly efficient OLED that exhibits CPEL signal, narrowband emission, and TADF concurrently.

Keywords: circularly polarized luminescence; multiple resonance; narrowband emission; organic light-emitting diodes; thermally activated delayed fluorescence.