Engineering Excited States of Pt-Based Deep-Blue Phosphors to Enhance OLED Stability

Platinum-based phosphorescent emitters have emerged as promising candidates for deep-blue OLEDs due to their high luminescence efficiency and narrow emission spectra. However, the insufficient chemical stability of blue phosphorescent emitters remains the primary obstacle to their commercial application. In this work, we present a systematic approach to enhance the stability of deep-blue emitters while preserving their optoelectronic properties. Using density functional theory calculations, we demonstrate that exciton-induced degradation via T₁→³MC transition is the primary operational degradation pathway for N-heterocyclic carbene-based tetradentate Pt-(II) complexes. To suppress this pathway, we developed two complementary strategies that destabilize the ³MC state while maintaining T₁ energy: (1) enhancing π-acceptance of the NHC moiety through electron-withdrawing substituents and (2) introducing steric hindrance via bulky groups on the pyridine ligand. Through systematic screening of PtON7 derivatives, we identified molecules with nearly doubled T₁-³MC energy gaps compared to the parent compound, achieving considerable stabilization while maintaining deep-blue emission characteristics. These findings establish rational design principles for developing commercially viable blue phosphorescent OLEDs.