(721b) Efficiency Limits of Underwater Solar Cells: An Excellent Application for Wide-Band-Gap Semiconductors?

Operation of underwater vehicles and autonomous systems is currently limited by the lack of long-lasting power sources. These systems could potentially be powered using underwater solar cells,^1–3 but the material requirements to achieve their full potential are not well-understood. Using detailed-balance calculations, we show that underwater solar cells can exhibit efficiencies from 55% in shallow waters to more than 65% in deep waters, while maintaining a power density > 5 mW cm^-2.⁴ We show that the optimum band gap of the solar cell shifts by ~0.6 eV (1.8 to 2.4 eV) between shallow and deep waters and plateaus at 2.1 eV at intermediate depths, independent of geographical location. This wide range in optimum band-gap energies opens the potential for the vast library of wide-band gap semiconductors to be used for high-efficiency underwater solar cells.

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