A photovoltaic apparatus includes an absorber including a p-layer having a bandgap greater than about 2 eV, an n-layer having a bandgap greater than about 2 eV, and an amorphous SiGe intrinsic layer between the p-layer and the n-layer; a first electrode adjacent to a first side of the absorber; a second electrode adjacent to a second side of the absorber; and an up-converter layer positioned adjacent to the second electrode on an opposite side of the second electrode from the absorber, wherein the up-converter layer includes a plurality of quantum dots of a first material in a matrix of a second material.