^Innovative Heterojunction Solar Cells Based on n-type ZnO / p-type Silicon Rafal Pietruszka, Bartłomiej S. Witkowski (Polish Acad Sci, Warsaw), E. Zielony, K. Gwozdz, E. Placzek-Popko (Wroclaw U.Sci.Tech., Poland), Marek Godlewski (Polish Acad Sci, Warsaw)