Narrow bandgap heterojunctions on crystalline silicon such as Si/Si 1−x Ge x are now in widespread use, but to date there has been little progress on widegap heterojunctions on silicon. In this abstract, we report: (i) TiO 2 /Si heterojunction with a band alignment which blocks holes from silicon but freely passes electrons, and (ii) the application of this heterojunction to form a photovoltaic cell on silicon with no p-n junction, and all fabrication below a temperature of 75 °C.