Photovoltaic effects of metalfree and zinc phthalocyanines. I. Dark electrical properties of rectifying cells

Abstract

The electrical properties of thin sandwich cells (M/Pc/Au) have been studied in a quantitative fashion. Here, M is either aluminum or indium (150–400 Å thick), and Pc represents metalfree phthalocyanine (H₂Pc) or its zinc complex (ZnPc). The phthalocyanines were ∼3000 Å thick. These devices were assembled by deposition in vacuo, but were studied by recording current–voltage curves in dry air. All showed rectification. Forward bias corresponded to a negative voltage at M. Cells with In contacts adhered quantitatively to expectations for Schottky junctions at the In/Pc boundaries. Cells with Al contacts passed much smaller currents under a given bias, and failed to behave quantitatively like Schottky junction devices. Various pieces of evidence indicate that the Al/Pc junction is spoiled by an interposed zone of Al₂O₃.