Solar cell processes and structures

A photovoltaic device is formed with a passivated first light receiving surface of a semiconductor material layer of a first doping type. A portion of oppositely doped semiconductor material is formed to produce a pn junction on at least a portion of a second surface located opposite to the first light receiving surface of the semiconductor material layer. First contacts are formed on the light receiving surface of the semiconductor material layer of the first doping type, and second contacts are formed on the oppositely doped material on the second surface of the semiconductor material layer. An n-type region is formed on a surface of the silicon semiconductor material by forming a layer of aluminum over the surface of the silicon material. The aluminum is then shock-heated at a temperature above the eutectic temperature of aluminum-silicon to form a p-type aluminum alloy semiconductor region. An epitaxial low-temperature solid phase growth process is then carried out at a temperature below the eutectic aluminum-silicon temperature, residual silicon in aluminum and / or alloyed region forms a p-type region to the aluminum-silicon interface by epitaxial solid phase growth.