Electron injection mechanisms of green organic light-emitting devices fabricated utilizing a double electron injection layer consisting of cesium carbonate and fullerene

Electron injection mechanisms of the luminance efficiency of green organic light-emitting devices (OLEDs) fabricated utilizing a cesium carbonate (Cs2CO3)/fullerene (C60) heterostructure acting as an electron injection layer (EIL) were investigated. Current density–voltage and luminance–voltage measurements showed that the current densities and the luminances of the OLEDs with a Cs2CO3 or Cs2CO3/C60 EIL were higher than that of the OLEDs with a Liq EIL. The luminance efficiency of the OLEDs with a Cs2CO3 EIL was almost three times higher than that of the OLEDs with a Liq EIL. Because the electron injection efficiency of the Cs2CO3 layer in OLEDs was different from that of the C60 layer, the luminance efficiency of the OLEDs with a double EIL consisting of a Cs2CO3 layer and a C60 layer was smaller than that of the OLEDs with a Cs2CO3 EIL. The electron injection mechanisms of OLEDs with a Cs2CO3 and C60 double EIL are described on the basis of the experimental results.