MIP-type organic solar cells incorporating phthalocyanine/fullerene mixed layers and doped wide-gap transport layers

We describe a simple organic solar cell structure that allows to study in detail loss mechanisms due to non-ohmic contacts, structural drawbacks and material selection: the MIP-type (metal-intrinsic-p-doped) structure discussed here represents the p-side and the active layer within a PIN type solar cell architecture. We here adapt the bulk heterojunction concept using blends of zinc-phthalocyanine (ZnPc) and buckminsterfullerene C-60. Furthermore, we use doped wide-gap materials as hole transport layers that enable a more sophisticated solar cell development. The samples are characterized by combination of current voltage characteristics, impedance spectroscopy and capacitance-voltage measurements. We present an evolution of MIP-type structures which improves all solar cell parameters; in particular, excessive series resistance and contact problems reducing the fill factor could be almost completely eliminated. (C) 2003 Elsevier B.V. All rights reserved.