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.

1. Jenkins, P.P., Messenger, S., Trautz, K.M., Maximenko, S.I., Goldstein, D., Scheiman, D., Hoheisel, R., and Walters, R.J. (2014). High-Bandgap Solar Cells for Underwater Photovoltaic Applications. IEEE J. Photovoltaics 4, 202–206.
2. Walters, R.J., Yoon, W., Placencia, D., Scheiman, D., Lumb, M.P., Strang, A., Stavrinou, P.N., and Jenkins, P.P. (2015). Multijunction Organic Photovoltaic Cells for Underwater Solar Power. 2015 IEEE 42nd Photovolt. Spec. Conf. PVSC 2015, 1–3.
3. Kong, J., Nordlund, D., Jin, J.S., Kim, S.Y., Jin, S.-M., Huang, D., Zheng, Y., Karpovich, C., Sertic, G., Wang, H., et al. (2019). Underwater Organic Solar Cells via Selective Removal of Electron Acceptors near the Top Electrode. ACS Energy Lett. 4, 1034–1041.
4. Röhr, J.A., Lipton, J., Kong, J., Stephen, A., and Taylor, A.D. (2020). Efficiency Limits of Underwater Solar Cells. Joule 4, 1–10.