A magnesium/amorphous silicon passivating contact for n-type crystalline silicon solar cells
Among the metals, magnesium has one of the lowest work functions, with a value of 3.7 eV. This makes it very suitable to form an electron-conductive cathode contact for silicon solar cells. We present here the experimental demonstration of an amorphous silicon/magnesium/aluminium (a-Si:H/Mg/Al) passivating contact for silicon solar cells. The conduction properties of a thermally evaporated Mg/Al contact structure on n-type crystalline silicon (c-Si) are investigated, achieving a low resistivity Ohmic contact to moderately doped n-type c-Si (∼5 × 10¹⁵ cm⁻³) of ∼0.31 Ω cm² and ∼0.22 Ω cm² for samples with and without an amorphous silicon passivating interlayer, respectively. Application of the passivating cathode to the whole rear surface of n-type front junction c-Si solar cells leads to a power conversion efficiency of 19% in a proof-of-concept device. The low thermal budget of the cathode formation, its dopant-less nature, and the simplicity of the device structure enabled by the Mg/Al contact open up possibilities in designing and fabricating low-cost silicon solar cells. ; This work was supported by the Australian Government through the Australian Research Council and the Australian Renewable Energy Agency (ARENA). Some facilities at the Australian National Fabrication Facility at the ANU were used.