Improvement of color purity and operational lifetime for PhOLEDs based on tetradentate Pt (II) complex

초록

In blue phosphorescent organic light-emitting diodes (PhOLEDs), achieving both high color purity and long operational stability remains a critical challenge. A new platinum (II) complex, PtON-tb-TPI, is developed by introducing a bulky ligand framework to control excited-state dynamics and host-dopant interactions. Density functional theory and molecular dynamics analyses reveal a reduced activation barrier for the metal-centered triplet to lowest triplet transition (3MC -> T1), small geometric displacement, and increased intermolecular distances in the emissive layer, which together suppress nonradiative decay and exciplex formation. Photophysical studies reveal that the introduction of bulky ligand effectively suppresses exciplex formation, leading to reduced spectral broadening and preserving the intrinsic narrow-band emission of PtON-tb-TPI. Devices incorporating PtON-tb-TPI as the blue emitter exhibit a narrow electroluminescence peak at 461 nm with a full width at half maximum of 21 nm (CIE y = 0.14) and achieve an operational lifetime (LT90) of 145 h at 1000 cd m- 2. These results highlight PtON-tb-TPI as a promising Pt(II) blue emitter and demonstrate an effective molecular design strategy for achieving stable, high color purity blue emission.

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