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lNovel lithium doped tris 8 hydroxylquinoline aluminium(Alq3:Li) layer is deposited between emission layer and electron injection aluminium electrode as an electron injection assistant layer in different organic light emitting diodes(OLED) to lower the electron injection barrier. In these devices, Alq3 is used as emission layer, and a bilayer film of N,N bis (1 naphhyl) N,N diphenyl 1,1 biphenyle 4,4“ diamine(NPB) and 4,4,4” tris(3 methyl phenylphenylamino) triphenylamine( m MTDATA) used as hole transport layer(HTL). The electroluminescent performance of devices with different thicknesses of Alq3∶Li shows that the insertion of the lithium doped Alq3 layer can reduce the turn on voltage by at least 2 volts, and the stability of devices with this lithium doped Alq3 layer is improved too. It can also change the efficiency of devices. Compared with an ultra thin lithium fluoride(LiF) layer, Alq3∶Li sheet gives similar effects but higher efficiency and can be much thicker and hence it is easier to control the deposition.
In these devices, Alq3 (Liq) 2 is an electron injection metal layer that emits electrons is used as an emission layer, and a bilayer film of N, N bis (1 naphhyl) N, N diphenyl 1,1 biphenyle 4,4 "diamine (NPB) 3 methyl phenylphenylamino) triphenylamine (m MTDATA) used as hole transport layer (HTL). The electroluminescent performance of devices with different thicknesses of Alq3: Li shows that the insertion of the lithium doped Alq3 layer can reduce the turn on voltage by at least 2 volts, and the stability of devices with this lithium doped Alq3 layer is improved too. Compared with an ultra thin lithium fluoride (LiF) layer, Alq3: Li sheet cy and can be much thicker and hence it is easier to control the deposition.