The present disclosure relates to a nanopillar tunneling photovoltaic (“NPTPV”), and method for fabricating it. The NPTPV device has a regular array of semiconductor pillar cores formed on a substrate having a conductive surface. Layers of high-k material are formed on the cores to provide an efficient tunneling layer for electrons (or holes) generated by incident photons in the cores. Transparent conductive collector layers are formed on the tunneling layer to collect the tunneled carriers. An optimized deposition process, various surface preparations, an interfacial layer between the pillars and the high-k tunnel layer, and optimized pre- and post-deposition annealing reduce the interface trap density and thus reduce recombination prior to tunneling. The absence of a junction also reduces core recombination, resulting in a high short-circuit current. Modifying the collector material and core doping tunes the open-circuit voltage. Such NPTPVs result in large-scale low-cost PVs.