A solar cell including a base of single crystal silicon with a cubic crystal structure and a single crystal layer of a second material with a higher bandgap than the bandgap of silicon. First and second single crystal transition layers are positioned in overlying relationship with the layers graduated from a cubic crystal structure at one surface to a hexagonal crystal structure at an opposed surface. The first and second transition layers are positioned between the base and the layer of second material with the one surface lattice matched to the base and the opposed surface lattice matched to the layer of second material.