The present invention relates to a low temperature method for making a photovoltaic material. In particular, the present invention describes a low temperature method for the deposition in vacuo of successive layers of materials required for a photovoltaic device. The present invention uses ion beam assisted processes in which a selected silicon containing precursor film is controllably converted to an amorphous silicon and carbon mixture. Ion beams are used to control the hydrogen content and thereby control the electrical conductivity of the material. The present invention further comprises the addition of a dopant and the deposition of the electrical contacts, both by thermal evaporation.