What is the efficiency limit of commercial single-junction silicon solar cells? The case for 50% single junction silicon solar cells

Achieving 50% efficient solar cells is typically considered well outside the possibility for a single-junction silicon photovoltaic solar cell, particularly a commercial silicon solar cell. The goal of this paper is to show that a combination of innovations can put silicon solar cells on a path to 50% efficiency using physical processes that have been physically observed but not optimized in structures consistent with commercial solar cells. A central feature of an ultra-high efficiency solar cell, and a critical challenge in making such devices, is the need for very thin solar cells below 10 microns. An ultra-thin solar cell allows the incorporation of other innovations, giving efficiencies approaching 50% using conventional physics and structures. Ultra-thin solar cells, in combination with other physical processes, such as nanostructured light trapping, allow new processes and further increase possible efficiencies. Overall, innovations include limited acceptance angles, low concentration, and effective light trapping, leading to an efficiency potential of 36% without sacrificing yearly energy generation. Adding the extraction of carriers at the quasi-Fermi level rather than the Fermi level and two-carrier generation gives an efficiency of up to 51%.