Electronic and chemical properties of cathode structures using 4,7-diphenyl-1,10-phenanthroline doped with rubidium carbonate as electron injection layers

Abstract

The electronic properties and chemical interactions of cathode structures using 4,7-diphenyl-1, 10-phenanthroline (Bphen) doped with rubidium carbonate (Rb2CO3) as electron injection layers were investigated. Current-voltage characteristics reveal that the devices with Bphen/Rb2CO3/Al as cathode structures possess better electron injection efficiency than those with cathode structures of Bphen/LiF/Al. Ultraviolet and x-ray photoemission spectroscopy shows that n-type doping effects resulting from Rb2CO3 and the gap states created by aluminum deposition are both keys to the improved carrier injection efficiency. Moreover, theoretical calculation indicates that the chemical reaction between aluminum and the nitrogen atoms in Bphen is the origin of the gap states.