Structured ZnO thin films grown by chemical bath deposition for photovoltaic applications

ZnO thin films have been deposited by chemical bath deposition (CBD-ZnO). The deposition conditions, i.e. the pH and the temperature of the bath, have been adjusted to achieve the deposition of porous, but adherent, thin films. After annealing in air half an hour at 300degreesC ZnO films crystallized in the hexagonal structure are obtained. They are nearly stoichiometric with a slight oxygen deficiency. The films are porous and the grains are columnar, which allows achieving films with large surface area. The films are semi-conductor with a n-type conductivity. It is shown that the grain boundary influence on the conductivity is stronger in longitudinal than in transversal structures. In the latter case the barrier height is nearly homogeneous. Such films deposited on ITO have been used in micro-structured solar cells with configuration ITO/ZnO/absorbent/aluminum. The absorbent used was an organic layer of zinc-phthalocyanine or a blend of poly(N-vinylcarbazole):diaminoanthraquinone. A photovoltaic effect has been achieved. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.