Platinum(ii) cyclometallates featuring broad emission bands and their applications in color-tunable OLEDs and high color-rendering WOLEDs

Abstract

Two phosphorescent platinum(II) cyclometallated complexes with phenoxy groups (1 and 2) have been developed. The modified organic ligands derived by combining the phenoxy moiety and 2-phenylpyridine conferred them with a more flexible structure, leading to superior intermolecular interaction properties of the resulting Pt(II) metallophosphors. Because of the excimer formation induced by Pt(II) complexes 1 and 2, the emission color can be tuned over a wide range from cyan to orange by simply increasing the concentration of the Pt(II) metallophosphors. Inspired by their broad emission band, color tunability and outstanding electroluminescence (EL) performance, these two Pt(II) phosphors complemented with blue fluorescent emitter 4,4′-bis(9-ethyl-3-carbazovinylene)-1,1′-biphenyl (BCzVBi) were employed in manufacturing high color-rendering white organic light-emitting devices (WOLEDs). In such simple two-emitter systems, 1-based WOLEDs exhibited reasonable EL performance with an external quantum efficiency (η_ext) of 11.7%, luminance efficiency (η_L) of 29.1 cd A⁻¹, power efficiency (η_p) of 16.9 lm W⁻¹ and color rendering index (CRI) of 77, whereas 2-based WOLEDs demonstrated an η_ext of 10%, η_L of 21.7 cd A⁻¹, η_p of 10.7 lm W⁻¹ and CRI of 88.