Efficient and Stable Deep-Blue OLEDs Employing Hot-Exciton Emitters with Rapid Exciton Dynamics: Achieving High EQEs Over 9% at 10 000 cd m−2 with CIEy <0.046

To achieve full-color displays with wide gamuts, developing high-performance deep-blue organic light-emitting diodes (OLEDs) with both high luminance and low efficiency roll-off is essential. Here, the study reports two new deep-blue emitters based on a crossed long-short axis (CLSA) molecular design strategy, incorporating a sp³-hybridized carbon bridge to create unique hybridized local and charge-transfer (HLCT) excited states. In addition to exhibiting high color-purity deep-blue emissions and high quantum yields in photoluminescence, these new emitters achieve excellent maximum external quantum efficiencies (EQEs) of 11.0% and 11.3% at CIE coordinates of (0.155, 0.039) and (0.155, 0.041), respectively. Furthermore, they maintain high EQEs of 9.3% and 9.1% at an ultrahigh luminance of 10 000 cd m⁻², representing the best performance reported to date for deep-blue OLEDs with CIEy ≤ 0.046. Theoretical calculations suggest these results originate from accelerated exciton dynamics via a dual-channel hot-exciton process, facilitated by the sp³-hybridized coupling mode that modulates excited-state behavior. This work demonstrates that adjusting the coupling mode between long and short axis in CLSA strategy has significant implications for improving device performance, especially in the development of high-performance deep-blue OLED emitters with high luminance and low efficiency roll-off.