High-Efficiency Polymer Light-Emitting Diode via Al Interfacial Modification Using Polyurethane

An efficient polymer light-emitting diode (PLED) was fabricated by inserting polyurethane (PU) between a poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene) layer and an Al cathode. The electroluminescence (EL) efficiency of the PU-based device can reach 1.27 cd/A, which is much higher than that of a device without PU (0.015 cd/A). The enhanced performance is attributed to both the hole-blocking capacity of the PU layer and the specific interaction between PU and the deposited Al, significantly facilitating the injection of electrons. Furthermore, the electron injection ability of PU-based devices was found to strongly depend on the thicknesses of the PU and Al layers.