High-brightness top-emissive polymer light-emitting diodes utilizing organic oxide/Al/Ag composite cathode

摘要

This work presents the fabrication of high-brightness (over 30 000 cd/m~2) top-emissive polymer light-emitting diodes (PLEDs) using a hybrid semitransparent cathode capable of efficient injection of electrons. The composite cathode is comprised of the organic oxide/Al complex as the injection buffer layer covered by a thin Ag overlayer. The anode is made of Ag: Ag_2O coated on the glass substrate. The electroluminescence (EL) efficiency of 8.9 cd/A for phenyl-substituted poly(para-phenylene vinylene) copolymer based top-emissive PLED markedly exceeds that of 4.3 cd/A for the control device with the bottom-emissive configuration, The high performance is attributed to the balanced injection of charge carriers and the effective extraction of EL emission from the top cathode. The optical microcavity effect significantly promotes the EL emission in the direction along the surface normal.