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

Abstract 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.