Improvement in performance of organic light-emitting diodes by interfacial engineering

We demonstrated a marked improvement in performance of organic light-emitting diodes (OLEDs) by interfacial engineering at electrode/ organic and organic/organic heterojunction interfaces. The use of an ultrathin 0.75-nm-thick MoO₃ layer between indium tin oxide (ITO) and N,N′-diphenyl-N,N′-bis(1-naphthyl) -1,1′-biphenyl-4,4′-diamine (α-NPD) drastically decreases the driving voltage of OLEDs and prevents OLED degradation at an ITO/α-NPD interface. We show that the insertion of a thin 5-nm-thick mixed layer of α-NPD and tris (8-hydroxyquinoline) aluminum (Alq₃) reduces the driving voltage and enhances the OLED stability as well. The decrease in driving voltage may reduce the generation of Joule heat and thus decrease thermally induced electrochemical decomposition of Alq₃.