Efficient white polymeric light-emitting diodes by doping ionic iridium complex

Abstract

A series of white polymer light-emitting diodes (WPLEDs) each with a single emitting layer using ionic iridium complex is fabricated. The white light is obtained via two complementary colors of orange light emitter ionic iridium complexe PF6 (Hnpy: 2-(naphthalen-1-yl)pyridine, c-phen: 1-ethyl-2-(9-(2-ethylhexyl)-9H-carbazol-3-yl)-1H-imidazo phenanthroline) and sky-blue light emitter Firpic (iridium bis(2-(4,6-difluorophenyl)-pyridinato-N,C(2)) picolinate. The emtting layer consists of poly(N-vinylcarbzole) (PVK) as host polymer, 1,3-bis -phenylene (OXD-7) as electron-transporting materials, Firpic and PF6. The structure of the WPLED is indium-tin-oxide/poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate)(40 nm)/emtting layer (80 nm)/CsF(1.5 nm)/Al(120 nm). When the mass ratio of PVK, OXD-7, Firpic, PF6 is 67 ∶23 ∶10 ∶0.25, the most efficient white light is obtained with a color coordinate of (0.31,0.40), a maximal luminance efficiency of 13.3 cd/A and a maximal luminance of 6032 cd/m2. Meanwhile, the color coordinate is unchanged with current density. The mechanism of the WPLED is discussed.