Highly Efficient Deep-Blue Phosphorescent OLEDs Based on a Trimethylsilyl-Substituted Tetradentate Pt(II) Complex.

Abstract

Compared to Ir(III) complexes with octahedral geometries, Pt(II) complexes with square planar geometries show superior optical properties because their flat shapes lead to an orientation that enhances the outcoupling of organic light-emitting diodes (OLEDs). However, the flat shapes of Pt(II) complexes typically induce a bathochromic shift, limiting their application in high-performance deep-blue phosphorescent OLEDs with high color purity. In this study, bulky trimethylsilyl (TMS)-substituted blue phosphorescent Pt(II) complex (PtON7-TMS) is successfully synthesized to improve color purity. The TMS substituent containing Si atom effectively suppresses intermolecular interaction and aggregation even when the complex concentration in the film state is higher than 30 wt %. As a result, the PtON7-TMS-based OLEDs exhibit a maximum external quantum efficiency of 21.4%, along with a pure-blue color of CIE (0.14, 0.09) at 20 wt % doping concentration and a full-width at half maximum of 30 nm. The pure blue color is maintained at a higher doping concentration (>30 wt %).