Fabrication of organic light-emitting diodes using LiF as a cathode injection layer

Organic light-emitting diodes using LiF as a cathode injection layer are fabricated by vapor thermal deposition.The diode with structure of ITO/TPD/Alq3/LiF/Al(TPD:N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'diamine,Alq3: tris(8-quinolinolato)-aluminum) performed better electroluminescent properties compared with the diodes without LiF layer.Experimental results showed that the insertion of ultra-thin LiF layer enhances the electron injection,reduces the turn-on voltage and improves the luminance and efficiency of diodes.The diode with a 0.5 nm LiF layer demonstrated the best performance,the turn-on voltage lowers to 5 V and efficiency increases to 3.3 cd/A in comparison with 9 V and 1.5 cd/A of the diode without LiF layer.However,the performances of diodes become worse with increasing thickness of LiF layer.