Single crystal Cu2O photovoltaics by the floating zone method

Cu2O is a p-type semiconductor with desirable bulk properties for photovoltaics. However, the lack of an n-type dopant and surface instability have hindered the development of a high efficiency Cu2O device. In this work, the floating zone method is used to grow high quality single crystals of Cu2O in order to controllably study the interfacial reactions between Cu2O and its heterojunction partners. While inclusions of CuO are inherent to the floating zone growth process we show that they can be removed by post-annealing with phase purity and crystallinity shown by x-ray diffraction. We discuss the role of CuO inclusions on the electronic properties of single crystal Cu2O wafers using Hall measurements. Changes in the resistivity and mobility due to post-annealing are correlated to changing defect densities obtained from steady-state photoluminescence. The optimization of the Cu2O wafers provides a pathway towards the first float zone single crystal Cu2O photovoltaic device.