New rhenium(i) complexes with substituted diimineligands for highly efficient phosphorescent devices fabricated by a solution process

Abstract

A series of new carbonyl rhenium(I) complexes chelated by a substituted 1,10-phenanthroline ligand with the general formula Re(CO)₃LCl, where L = 2-(2′-methoxyphenyl)-1,10-phenanthroline (L₁1), 2-(4′-methoxyphenyl)-1,10-phenanthroline (L₂2) and 2-(4′-diphenylaminophenyl)-1,10-phenanthroline (L₃3), have been systemically synthesized. The molecular structure of complex 1 was determined by single crystal X-ray diffraction studies, showing that the complex adopts a distorted octahedral geometry. The electrochemical, photophysical, and thermal properties, as well as the electroluminescent behaviors of three rhenium(I) complexes, were investigated. The solution processable complex 1, 2 or 3 was used as a yellow emitting dopant to fabricate electrophosphorescent devices with a polymer host. The device based on complex 3 exhibits a maximum current efficiency of 12.2 cd A⁻¹ and a peak brightness in excess of 7300 cd m⁻², respectively. Even at a high luminance of 5000 cd cm⁻² with current density of 81 mA cm⁻², the current efficiency of this device remains as high as 6.4 cd A⁻¹. These results represent the best values reported for electophosphorescent devices based on solution processable rhenium(I) complexes.