Engineering B‒N Covalent Bond-Fused Naphthalene Derivatives for Narrowband Yellow Emission and Power-Efficient White OLEDs.

The doping of B‒N covalent bond into multiple resonance (MR) emitters is believed to enable easy synthesis while maintaining the intrinsic narrow spectral profile for high-definition organic light-emitting diodes (OLEDs). However, there is still an unexplored spot if the residual MR section is further removed. Herein, the molecular engineering of B‒N covalent bond-fused naphthalene derivatives is demonstrated that are free of MR for yellow emission with a reduced spectral bandwidth and power-efficient white OLEDs. Starting from the BN-nap1 reference, a dual fusion strategy is proposed to design two new yellow emitters, BN-nap2 and BN-nap3, by integrating B‒N bonds with naphthalene via a centro and axial symmetry, respectively. Both of them exhibit significantly red-shifted light to the yellow region, decreased full width at half maximum, improved photoluminescent quantum yield, due to the B-naphthalene-B conjugation and suppressed high-frequency vibrations. As a result, the corresponding warm white devices achieve a record-high power efficiency of 101.4 lm W-1 at 1000 cd m-2 and Commission Internationale de l'Éclairage (CIE) coordinates of (0.342, 0.542). Further device optimization leads to a standard white electroluminescence with CIE coordinates of (0.334, 0.342). The unprecedented performance indicates the great potential of B‒N covalent bond-fused naphthalene derivatives in power-efficient white OLEDs.