Cyano-Substituted Platinum(II) Complexes for Highly Efficient Deep-Blue Phosphor-Sensitized Fluorescent OLEDs

초록

Tetradentate Pt(II) complexes are promising phosphorescent materials for achieving high-performance deep-blue organic light-emitting diodes (OLEDs). However, their molecular designs have traditionally relied on incorporating complex, bulky substituents to prevent stacking-induced photophysical anomalies arising from their inherently planar structures. Here, we present a simple yet highly effective alternative: introducing a non-bulky cyano (CN) group at the para-position of the Pt-phenyl bond. This subtle modification not only suppresses exciplex emission but also enhances the photoluminescence quantum yield by mitigating both temperature-dependent and temperature-independent nonradiative decay processes. Utilizing the CN-substituted Pt complex as a phosphorescent sensitizer, paired with a multi-resonance thermally activated delayed fluorescent emitter, we demonstrate a deep-blue phosphor-sensitized fluorescent (PSF) OLED achieving a maximum external quantum efficiency (EQE) of 31.7% +/- 0.9% and a Commission Internationale de l'& Eacute;clairage y-coordinate below 0.1. Notably, the PSF OLED sustains a high EQE of 25.4% +/- 0.8% even at the practical luminance of 1000 cd/m2. This simultaneous achievement-remarkable given the persistent trade-off between efficiency and spectral purity in the deep-blue regime - establishes a simple yet powerful strategy for advancing efficient deep-blue OLEDs based on Pt(II) complexes.

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