Space‐Charge‐Limited Current and Band Structure in Amorphous Organic Films

Abstract

Electrical conduction phenomena in thin films of some organic polymers have been investigated. The current‐voltage characteristics of polymethylmetacrilate, polyvinylformal, and polyethylene‐terephthalate films display a space‐charge‐limited current (SCLC). The steady‐state SCLC and the back current are interpreted in terms of an energy band model with localized states uniformly distributed in energy within a region of the forbidden band. This region is (0.353 + 0.025) eV wide and seems to be independent of the chemical nature of the amorphous material, the sample preparation procedure, and the sample thickness. The density per unit energy of localized states ranges from 10¹⁴ to 10¹⁸ cm⁻³ eV⁻¹.