Orbital Symmetry Engineering in Fused Polycyclic Heteroaromatics toward Extremely Narrowband Green Emissions with an FWHM of 13nm.

Abstract

Multiresonance (MR) molecules generally face spectral broadening issues with redshifted emissions. Thus, green emitters with full widths at half maximum (FWHMs) of <20nm are rarely reported, despite being highly desired. Herein, by properly fusing indolo(3,2,1-jk)carbazole (ICZ) and naphthalene moieties, green MR emitters are reported, which have FWHMs of merely 13nm (0.064eV) and 14nm (0.069eV) in dichloromethane, accompanied by high photoluminescence quantum yields of >95%, which represent not only the smallest FWHMs among all green MR emitters but also the first green emitters based on ICZ MR derivatives. Theoretical studies reveal that the orbital interactions between the antisymmetric sites of the segments play an important role in extending the conjugation length in the fusion architectures while simultaneously maintaining a small FWHM. The corresponding organic light-emitting diodes exhibit green emission peaks at 508-509nm and the first green electroluminescence FWHM of <20nm ever reported. Benefiting from the preferential horizontal dipole orientation, a high maximum external quantum efficiency of up to 30.9% is obtained, which remains at 28.9% and 23.2% under luminances of 1000 and 10000 cdm-2 , respectively, outperforming most reported green devices based on narrowband emitters.