Abstract
The development of ultra-high-definition organic light-emitting diodes (OLEDs) displays requires efficient and narrowband blue emission. Nevertheless, binary host-guest doped narrowband blue OLEDs still face significant challenges in simultaneously realizing high efficiency and negligible roll-off. Herein, a molecular construction strategy through the synergistic interplay between π-conjugation extension and functional complementarity fusion is proposed by incorporating a rigid boron-oxygen (BO) framework with carbazole building blocks. The constructed compounds exhibit increased triplet exciton recycling capability, high excited-state energy levels, and improved charge transporting features, showcasing significant potential as host matrices for blue devices. The sensitizer-free OLEDs achieve the narrowband blue emission with a CIEy value lower than 0.15, a maximum external quantum efficiency of 41.2%, and the suppressed efficiency roll-off at high luminance due to efficient energy transfer to blue guest emitters and elevated horizontal dipole orientation. This work strategically demonstrates a balance between high efficiency and reduced efficiency roll-off in binary narrowband blue OLEDs, representing a substantial advancement in blue electroluminescent technology.