Homoleptic tris-cyclometalated iridium complexes with 2-phenylbenzothiazoleligands for highly efficient orange OLEDs

Abstract

Homoleptic tris-cyclometalated iridium(III) complexes containing 2-phenylbenzothiazole derivatives as ligands have been successfully synthesized and characterized for the first time. Electron-donating (CH₃, OCH₃) and -withdrawing groups (F) were introduced into the 6-position of the benzothiazole moiety in the ligands to verify their influence on the optical and electronic properties of the complexes. Organic light-emitting diodes using these iridium complexes as doped emitters exhibited orange electrophosphorescence with excellent performances. An extremely high brightness of 95 800 cd m⁻² and a maximum luminance efficiency of 87.9 cd A⁻¹ (46.0 lm W⁻¹) were achieved for the pristine complex without any substituent in the ligand. These performances represent a significant improvement for vacuum-deposited orange OLEDs and the new record of the efficiencies for orange OLEDs reported so far. The substituents in the ligand were observed to be rather unimportant to influence the performance of this series of iridium complexes.