Synergistic Enhancement of Emitting Dipole Orientation between Pt‐Based Phosphorescent Sensitizers and Boron‐Based Multi‐Resonance Fluorescent Emitters for High‐Performance Phosphor‐Sensitized Fluorescent Organic Light‐Emitting Diodes

Phosphor‐sensitized fluorescent (PSF) organic light‐emitting diodes (OLEDs) emerge as an attractive solution for realizing high‐performance displays with high color purity, meeting the Broadcast Television 2020 (BT.2020) requirements, by fully harnessing the benefits of both phosphorescent and fluorescent emitters. Herein, the synergistic effect of a Pt sensitizer and a boron (B)‐based multi‐resonance (MR)‐fluorescent emitter are introduced to enhance the efficiency of blue‐emitting PSF–OLEDs. Notably, it is confirmed that the interaction between the empty pz orbital in the boron atom of the MR emitter and the unpaired electrons in the dz2 orbital of the Pt emitter plays a crucial role. The combination results in an enhancement of the horizontal emitting dipole orientation (EDO) to 81%, a marked improvement compared to the individual components of Pt phosphor (69%) or MR emitter (78%). The synergistic approach leads to the realization of high‐performance blue‐emitting PSF‐OLEDs with a maximum external quantum efficiency of 25%, a peak intensity at 465 nm in the electroluminescence spectrum, and a full width at half maximum of 29 nm, achieved by enhancing the outcoupling. In these findings, insight is provided into design strategies for developing PSF systems based on Pt sensitizer and B‐terminal emitter to achieve efficient energy transfer as well as improved EDO.