A ［2-methyl-6-［2-(2, 3, 6, 7-tetrahydro-1H, 5H-benzo［ij］ quinolizin-9-yl) ethenyl］-4H-pyran-4-ylidene］ propane-dinitrile (DCM2) sub-monolayer was inserted in the electron transporting layer of organic light emitting devices (OLEDs). Based on the different position of deposited DCM2 sub-monolayer, the electroluminescence (EL) spectra，brightness intensity and current efficiency of these four devices show that DCM2 sub-monolayer located at the N,N′-bis-(1-naphthyl)-N, N′-diphenyl-1, 1′-biph-enyl-4, 4′-diamine(NPB)/(8-hydroxyquinoline) aluminium(Alq) hetero-junction interface obtained most excitons. The obtained results will be helpful for the optimal design and operation of OLEDs.