Achieving near-infrared electroluminescence around 780 nm based on butterfly-shaped dinuclear platinum(ii) complexes

Abstract

Organic near-infrared (NIR) phosphorescent materials, especially platinum complexes, still attract the attention of researchers due to their excellent performance. However, most of the high-efficiency mononuclear cyclometalated platinum complexes in NIR-OLEDs are derived from intermolecular excimer emission except for porphyrin–platinum complexes. The problem is that aggregated emission heavily relies on solid-state packaging technology, which poses challenges to preparation conditions and performance optimization of devices. Employing dinuclear platinum complexes as dopants for solution processed devices is regarded as one of the methods to solve this problem and achieve intrinsic long wavelength emission. Here, we report a class of dinuclear platinum complexes Pt1 and Pt2 which have a butterfly-shaped three-dimensional structure and a cyano (CN) group on the main ligand. Importantly, maximum external quantum efficiencies (EQE_max) of 2.73% and 2.62% around 780 nm at a low doping concentration of 2.0 wt% were achieved for Pt1 and Pt2 based NIR-OLEDs. Our results demonstrate that butterfly shaped dinuclear platinum complexes obtained by cyanidation can be potential candidates for achieving solution processed long wavelength NIR-OLEDs.