Unveiling the Centrosymmetric Effect in the Design of Narrowband Fluorescent Emitters: From Single to Double Difluoroboron Cores

Abstract

Narrowband fluorescent emitters are receiving significant attention due to the great potential for creating ultrahigh-definition organic light-emitting diode displays (UHD-OLED). Unveiling innovative mechanisms to design new high-performance narrowband fluorescent emitters is a concerted endeavor in both academic and industrial circles. Theoretical calculations reveal that the centrosymmetric dianilido-bipyridine boron difluoride framework (cs-DAPBF₂) exhibits significantly reduced structural relaxation compared to previously reported asymmetric structures with monofluoroboron cores, creating new opportunities for the development of narrowband fluorescent emitters. In this work, we present a dual chelation-assisted C–H/C–H homocoupling strategy to efficiently synthesize the 3,3′-amino-2,2′-bipyridine skeleton, enabling the straightforward construction of a series of symmetric cs-DAPBF₂-based fluorescent emitters. Through molecular optimization, we have developed a high-performance narrowband green fluorescent emitter, cs-DMeAPBF₂-MP, which demonstrates a narrow full width at half-maximum (fwhm) of 20 nm, a high photoluminescence quantum yield (Φ_PL) of 98%, a large molar absorptivity (ε) of 2.10 × 10⁴ M^–1 cm^–1, and a high horizontal dipole ratio (Θ_//) of 77%. These properties make cs-DMeAPBF₂-MP a promising candidate for fabricating high-efficiency, narrowband green organic light-emitting diodes (OLEDs) with minimal efficiency roll-off. This study represents the first successful application of the DAPBF₂ architecture in the design of narrowband fluorescent emitters for high-performance OLEDs.