Interfacial charges and electric field distribution in organic hetero-layer light-emitting devices

Abstract The electric field distribution in organic hetero-layer light-emitting devices based on N,N′-diphenyl-N,N′-bis(1-naphtyl)-1,1′-biphenyl-4,4′-diamine (NPB) and 8-tris-hydroxyquinoline aluminium (Alq3) has been investigated under different bias conditions using capacitance–voltage measurements. Although this method yields primarily information on the differential capacitance, the data give clear evidence for the presence of negative interfacial charges with a density of 6.8×10 11 e cm −2 at the NPB/Alq3 interface at large reverse bias. This leads to a jump of the electric field at the interface and a non-uniform field distribution in the hetero-layer device.

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