TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The back contact semiconductor material layer is in direct contact with the bottom surface of the absorption layer. The front contact semiconductor material layer is in direct contact with the top surface of the absorption layer. The silicon-containing semiconductor layer of the first conductivity type comprises crystalline or multi-crystalline silicon. The back or front contact semiconductor material layer each comprises germanium or a silicon-germanium alloy which is: amorphous and hydrogenated; and nano/microcrystalline or polycrystalline. The first conductivity type is p-type, where the back contact semiconductor material layer has a higher concentration of p-type dopants than the absorption layer. The photovoltaic device further comprises: a back contact intrinsic semiconductor material layer positioned between the bottom surface of the absorption layer and the back contact semiconductor material layer; and a hydrogenated amorphous semiconductor layer positioned between the intrinsic layer and the back contact semiconductor material layer. The contact semiconductor material layer comprises a first back contact semiconductor material layer and a second back contact semiconductor layer, where the first and second back contact semiconductor material layers are of different composition. In the device (D1), the first conductivity type is n-type, and the second conductivity type is p-type. The photovoltaic device (D1) further comprises: a front contact intrinsic semiconductor material layer positioned between the top surface of the absorption layer and the front contact semiconductor material layer; and a hydrogenated amorphous semiconductor layer positioned between the intrinsic layer and the front contact semiconductor material layer. The front contact semiconductor material layer comprises a first front contact semiconductor material layer and a second front contact semiconductor layer, where the first and second front contact semiconductor material layers are of different composition. The first back or front contact semiconductor material layer comprises germanium and the second back or front contact semiconductor layer comprises a silicon-germanium alloy.