Single crystal Cu_2O photovoltaics by the floating zone method

Abstract

Cu_2O 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 Cu_2O device. In this work, the floating zone method is used to grow high quality single crystals of Cu_2O in order to controllably study the interfacial reactions between Cu_2O 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 Cu_2O 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 Cu_2O wafers provides a pathway towards the first float zone single crystal Cu_2O photovoltaic device.

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