Solar Cell Design Principles

The two key metrics in photovoltaics are cost and efficiency. Wavelength-scale design has the potential to make improvements along both axes. In earlier work we studied the photon dynamics inherent to the Shockley–Queisser (SQ) limits, and found that there was a large and nonlinear penalty to any imperfections within the cell. We introduced a generalized bound with a new parameter incorporating such imperfections; the physical insight, connecting open-circuit voltage to photon dynamics, provided the foundation for Alta Devices to break the single-junction solar cell efficiency record. After twenty years of slight improvement in record efficiencies (25.1% to 26.4%), Alta achieved 28.8% efficiency, entirely through open-circuit voltage enhancement. 
More broadly, there is a never-ending push to find cheaper materials and architectures that achieve higher efficiencies. We have leveraged computational design to find sub-wavelength-scale surface textures that achieve record high-index broadband absorption enhancement, and we foresee many areas for improvement in the near to medium term.
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