Tuning the energy levels and photophysical properties of triphenylamine-featured iridium(iii) complexes: application in high performance polymer light-emitting diodes

Abstract

A new triphenylamine-based homoleptic iridium(III) complex is designed and synthesized by simply altering the ligation positions of the triphenylamine units. The theoretical calculations reveal that the difference in the ligation position has a significant influence on the optical and electronic properties of the complexes. Through dispersing the green phosphor G-Ir into PVK in the presence of an electron-transport material, 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD), the green phosphorescent device achieves maximum current/power/external quantum efficiencies of 43.8 cd A⁻¹/20.5 lm W⁻¹/15.1%. The new green phosphor and its counterparts OO-Ir and R-Ir have been demonstrated as active components for white polymer light-emitting diodes (WPLEDs). A single-layer white light-emitting device is fabricated by doping the sky-blue emitter iridium(III) bis(2-(4,6-difluorophenyl)-pyridinato-N,C²)picolinate (FIrpic), G-Ir, OO-Ir and R-Ir into a general polymer matrix, with the maximum current/power/external quantum efficiencies of 23.5 cd A⁻¹/12.0 lm W⁻¹/8.6%, which are comparable with the best results obtained from the conventional RGB primary color system under the same device structure.