Molecular Beam Epitaxy of Cu_2O Heterostructures for Photovoltaics

Cu_2O is a p-type semiconductor that has demonstrated attractive photovoltaic properties, but its efficiencies have been limited by surface instability and lack of high quality thin films. In this work, plasma-assisted molecular beam epitaxy is used to precisely control film orientation and interface chemistry of Cu_2O heterostructures. Thin films of Cu_2O are deposited by MBE onto thin films of Pt and Au sputtered on MgO single crystal substrates. This heterostructure configuration provides a path for an all-epitaxial thin film Cu_2O solar cell, which can serve as a top cell in a tandem structure with a crystalline Si bottom cell.