A chiral co-assembled exciplex host achieved extremely outstanding narrowband circularly polarized electroluminescence

High-performance circularly polarized organic light-emitting diodes (CP-OLEDs) that can simultaneously achieve narrowband emission and high electroluminescence asymmetry factor (g _EL) values remain a formidable challenge. In this study, a simple strategy utilizing a co-assembled chiral exciplex as a host material was employed to fabricate high-performance CP-OLEDs. The exciplex was constructed from chiral acceptor enantiomers (R/S-TRZ) and an achiral liquid-crystalline donor (CzTPA). Upon thermal annealing, the resulting co-assembled films exhibited circularly polarized luminescence (CPL) with a luminescence asymmetry factor (g _lum) up to 0.58. Introducing the achiral green multiple-resonance thermally activated delayed fluorescence (MR-TADF) emitter to the exciplex host enabled high-performance circularly polarized electroluminescence (CP-EL). The resulting device exhibited a large g _EL value of 0.28, a narrow full width at half-maximum (FWHM) of 33 nm, and negligible efficiency roll-off. This work describes the first case of narrowband CP-OLEDs based on chiral co-assembled exciplex host materials, representing one of the highest g _EL values of reported narrowband emission CP-OLEDs to date. It further establishes a general strategy for fabricating high-performance CP-OLEDs with readily available achiral emitters, thereby significantly broadening applications in chiral optoelectronics.