The down-to-earth future of Si substrate multi-junction concentrator photovoltaics

The high costs of multi-junction (MJ) cells are a barrier to transferring MJ technology from space to terrestrial Concentrator Photovoltaic (CPV) markets. This may be addressed with significant impact by transitioning from Ge to Si substrates. By exploiting reduced material costs, new manufacturing practices including automation and revised quality standards, and by leveraging manufacturing efficiencies inherent to larger wafer sizes, up to 200 mm, the selection of Si as the substrate material allows for reductions potentially as large as 70% of current values. It is possible to demonstrate how plausible reductions to system costs (22 - 40%), in combination with very conservative cell cost reductions, make achieving competitive Cost of Electricity (COE) values in the order of $0.10/kWh a likely scenario in the near future for MJ CPV. Impending increases to conversion efficiencies (up to 50%), exploited conjointly with stated cost reduction factors (particularly system cost reduction), promise to drive COE values lower still, potentially under $0.08/kWh.