P‐260: <i>Late‐News Poster:</i> Enhancing the Stability of Deep Blue Phosphor‐Sensitized Fluorescent OLED Using Polariton‐Enhanced Purcell Effect

The stability of efficient, deep blue organic light‐emitting diodes (OLEDs) remains a major challenge in organic electronics and industry. The poor device stability originates from the high probability of non‐radiative triplet exciton annihilation. Phosphor‐sensitized fluorescence (PSF) has been proposed to reduce triplet exciton density and enable deep blue emission by efficient energy transfer to fluorophores. Recently, the polariton‐enhanced Purcell (PEP) effect has been introduced to decrease the triplet radiative lifetime, thereby reducing reduce triplet density resulting an increase in blue phosphorescent OLED lifetime. Here, we introduce the PEP effect to enhance the stability of the PSF‐OLEDs. Applying a full PEP cavity to the device using Pt‐complex phosphor and a so‐called multi‐resonance (MR) fluorescent emitter, we observe a 3.1‐fold lifetime increase at a current density of J = 10 mA/cm 2 . reduced EQE roll‐off and a deep blue color with Commission Internationale de l'Eclairage coordinates of (0.13, 0.09).