Single crystal and amorphous Ge for use in stand-alone and thin film tandem solar cells

Thin film and single crystal germanium solar cells are of interest for use in low cost thermophotovoltaics [1,2] and in multijunction solar cells. Single crystal Ge substrates have been utilised for the growth of high-efficiency III-V concentrator solar cells which have achieved high efficiencies [3]. In this paper, we consider the use of crystalline Ge as bottom cell and substrate for growth of high efficiency II-VI multijunction solar cells and amorphous Ge for application in thin film II-VI tandem solar cells.