Organic cesium salt as an efficient electron injection material for organic light-emitting diodes

Cesium quinoline-8-oxide (Csq), as an organic salt, was synthesized and applied as an electron injection material for organic light-emitting diodes. A typical bilayer structure of N,N-'-bis-(1-naphthyl)-N,N-'-diphenyl-1,1(')-biphenyl-4,4(')-diamine/tris-(8-hydroxy-quinolinolato) aluminum (III) (Alq(3)) was used to evaluate the electron injection of Csq. The results showed Csq/Al had better electron injection than LiF/Al cathode, and a maximum current efficiency of 4.13 cd/A (3.33 cd/A for LiF/Al) was obtained when the Csq layer is 2.0 nm. It is proposed that the enhanced electron injection by Csq is related to the interfacial chemical reaction between Csq and Al and the self-doping of Csq by librated Cs.