Efficient Silole-Based Organic Light-Emitting Diodes Using High Conductivity Polymer Anodes

High luminance organic light-emitting diodes (OLEDs) with a relatively low operating voltage are presented using a conducting polymer [without an indium-tin oxide (ITO) underlayer] as a hole-injecting electrode (anode) and silole derivatives as an emitter and/or an electron transporter. The conducting polymer films of poly(3,4ethylenedioxythiophene)-poly(styrenesulfonate) were either spin-cast from aqueous dispersions on glass substrates or supplied as precoated films on poly(ethylene terephphalate) substrates. The films obtained by spin casting on glass substrates show very low sheet resistance (150 (omega)/sq). OLEDs fabricated using this conducting polymer as an anode without using an ITO underlayer and CsF/Al as a cathode exhibit very low operating voltages (6.5 V at 1000 cd/m^2). The silole derivative, 2,5-bis-(2ʹ,2ʹʹ-bipyridin-6-yl)-1,1-dimethyl-3,4-diphenylsilacyclopentadiene, used as an electron transporter, forms an Ohmic contact with the electroninjecting electrode (CsF/Al), leading to efficient electron injection. This contributes to better charge balance and improved device efficiency.