Efficient white polymer light-emitting diodes employing a silver nanowire–polymer composite electrode

Abstract

White polymer phosphorescent light-emitting diodes have been fabricated employing silver nanowire (AgNW)–polymer composite substrates. Solution processing is used to form all the layers in the devices, except for the cathode, for potentially low fabrication cost. The current efficiency in the front viewing direction is 20.3 cd A⁻¹ for devices comprising two complementary dopants (bis[(4,6-difluorophenyl)-pyridinato-N,C²] (picolinato)Ir(III) (FIrpic) with sky blue emission and bis(1-phenylisoquinoline)(acetylacetonate) (Ir(piq)) for red emission). The efficiency is 42.3 cd A⁻¹ at 4000 cd cm⁻² for devices comprising the three primary colors (FIrpic, Ir(piq), and tris(2-(4-tolyl)pyridinato-N,C²) (Ir(mppy)₃), with green emission). These values are, respectively, 35% and 41% higher than those of control devices fabricated on indium tin oxide (ITO) coated on glass substrates. The enhanced current efficiency is attributed to enhanced light out-coupling thanks to light scattering by the silver nanowires embedded in the transparent composite electrode.