Stability enhancement of blue organic light-emitting diodes through exciton-density-dependent degradation analysis and triplet management.

Abstract

Achieving long operational stability in blue organic light-emitting diodes (OLEDs) remains a challenge. Bond dissociation energy (BDE) is widely used to evaluate molecular robustness, yet it mainly reflects static chemical stability and does not account for exciton- and polaron-related degradation in operating devices. A semi-quantitative exciton-density-dependent degradation framework is developed by combining intrinsic BDE with activation-energy analysis to rationalize emitter stability under electrical excitation. The analysis indicates that the stability window of anthracene-based blue triplet-triplet annihilation (TTA) systems is affected by both intrinsic bond strength and the steady-state populations of triplet excitons and polarons. Triplet-related bond cleavage serves as a critical degradation channel, which tightens the BDE requirement. Reducing local polarons/triplet accumulation lowers the exciton-induced activation-energy contribution, mitigates bimolecular quenching, and broadens the design space for stable blue emitters. Following this principle, dual-emissive-layer blue TTA OLEDs were constructed to redistribute recombination and triplet-utilization zones, achieving a high blue index (BI ≈ 255 cd A^-1/CIEy at J = 10 mA cm^-2) and improved operational stability (LT95 = 46.18 h at 5300 cd m^-2, extrapolated LT95 = 854.94 h @ 1000 cd m^-2). These results highlight the importance of triplet-density management in stable blue OLEDs and provide qualitative guidance for exciton-management strategies in related OLED systems.