Boosting the Stability of the Efficient Tandem Blue Organic Light-Emitting Diodes Using Plasmon-Exciton-Polaritons

Over the decades, short operational lifetimes of blue organic light-emitting diodes (OLEDs) stand out as one of the greatest challenges in organic electronics. Plasmon-exciton-polaritons (PEPs), a quasiparticle formed by the strong coupling between the plasmons in the metal and the excitons in an adjacent dielectric material, have been recently introduced to extend the lifetime of blue phosphorescent OLEDs[SF1] [1]. The PEP-enhanced Purcell effect has achieved 5-6X enhancement in device stability by reducing the phosphor triplet density, thereby slowing down destructive triplet annihilation processes. In previous studies, the stability of the emissive layers was enhanced via the strong coupling between the cathode and the adjacent electron transporting layer (ETL). Here, we introduce the polariton-enhanced Purcell effect from the anode and the hole transporting layer (HTL) to achieve the device lifetime enhancement from both the anode and cathode contacts in tandem blue PHOLEDs. We show that full-cavity tandem blue OLEDs with double-sided PEP-enhanced Purcell effects achieve a 10X increase in device lifetime compared to weak-cavity tandem devices. A tandem OLED structure shows a 3X increase compared to a single stack device due to a 50% reduction in current needed to achieve the same luminance as a single junction device. Furthermore, the full-cavity device narrows the emission spectrum useful in blue display pixels. Taken together, these polariton-enhanced Purcell effect full-cavity tandem device shows a 30X longer device lifetime in deep blue over an analogous, single-stack device.<br/><br/>[1] H. Zhao, C. E. Arneson, D. Fan, and S. R. Forrest, <i>Stable Blue Phosphorescent Organic LEDs That Use Polariton-Enhanced Purcell Effects</i>, Nature 0 (2023).