Electronegativity model for barrier formation at metal/organic interfaces

An electronegativity model is proposed to characterize the variation of charge injection barrier heights at metal/organic interfaces. In contrast to the traditionally used metal work function, barrier heights at interfaces are shown to be linearly dependent on metal electronegativity for a wide range of organic materials. The physical basis for the better suitability of electronegativity than work function to describe barrier heights is discussed. While barrier formation is caused by charge transfer between metals and organic semiconductors, the variation of the barrier height is related to the electronegativity difference of metals. The applicability of the electronegativity model to compound or alloy electrodes, such as indium tin oxide having no defined electronegativity, is also exemplified. © 2005 American Institute of Physics.