Facile access to spirobifluorene-fused chiral multi-resonance materials with ultra-narrowband blue emission

Narrowband multiple resonance (MR) emitters with circularly polarized luminescence (CPL) hold significant promise for three dimension organic light-emitting diode (3D-OLED) displays. In this work, we present a simple method for developing a new type of 9,9'-spirobifluorene-based CP-MR emitters by a recrystallization resolution technology and chlorine (Cl)-directed electrophilic borylation reaction, both of which significantly enhance the efficiency and scalability for mass production. This approach allows for integrating an asymmetric 9,9'-spirobifluorene core between two MR frameworks to achieve optically active CP-MR emitters. The highly rigid spirobifluorene framework minimizes structural relaxation, and meanwhile, the introduction of a cyano (CN) group enhances the MR emission characteristics, leading to an ultra-narrowband blue emission with full width at half maximum (FWHM) of 14 nm. As a result, these molecules facilitate the assembly of narrowband blue CPL-OLEDs with a maximum external quantum efficiency (EQE_max) of 30.7% and an impressive narrow FWHM of 16 nm, representing the first instance of an FWHM below 20 nm in CPL-OLEDs.