The fine adjustment of the organic absorber nanoscopic properties, such as crystallite orientation, dimension and separation distance is demonstrated. This is essential for organic solar cells based on bulk and three-layered molecular heterojunctions for well controlled and reproducible properties. The required structures are achieved by using the organic vapor-phase deposition technique. Homogeneously nanostructured donor copper phthalocyanine layers are grown as a function of process parameters as columnar and/or horizontal elongated-rodlike crystallites on single crystalline < 100 >-oriented Si wafers as well as 3,4-polyethylenedioxythiophene:polystyrenesulfonate-coated indium tin oxide/glass substrates. The influence of the CuPc crystallinity on the photovoltaic properties of the organic solar cell devices is investigated. (c) 2007 Elsevier B.V. All rights reserved.