Methods, systems, and devices are disclosed for implementing high conversion efficiency solar cells. In one aspect, an optical-to-electrical energy conversion device includes a substrate formed of a doped semiconductor material and having a first region and a second region, an array of multilayered nanoscale structures protruding from the first region of the substrate, in which the nanoscale structures are formed of a first co-doped semiconductor material covered by a layer of a second co-doped semiconductor material forming a core-shell structure, the layer covering at least a portion of the doped semiconductor material of the substrate in the second region, and an electrode formed on the layer-covered portion of the substrate in the second region, in which the multilayered nanoscale structures provide an optical active region capable of absorbing photons from light at one or more wavelengths to generate an electrical signal presented at the electrode.