Field effects in the saturation region of space charge limited current in molecular crystals

Abstract

Current-voltage curves in the saturation region of hole injection from aqueous Ce(SO₄)₂, KI₃, and SnCl₄ solutions into anthracene are reported. These, and some curves for similar systems appearing in the literature, contrast with the prediction of a flat saturation region from the theory developed by Mehl and Hale. They are inter- preted in terms of field assisted emission from the surface into the bulk of the crystal, although in some systems, particularly Ce(SO₄), 1 anthracene, two mechanisms appear to operate. In an Appendix the effects of space charge on the shape of the saturation curve are shown to be small, except near the saturation point in some cases.