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.
Select publications:
- Strong internal and external luminescence as solar cells approach the Shockley–Queisser limit, O. D. Miller, E. Yablonovitch, and S. R. Kurtz, IEEE J. Photovoltaics 2, 303–311 (2012)
- The opto-electronics of solar cells, E. Yablonovitch and O. D. Miller, IEEE Photonics Soc. News (Research Highlight) 27, 4–5 (2013)
- Light trapping textures designed by electromagnetic optimization for subwavelength thick solar cells, V. Ganapati, O. D. Miller, and E. Yablonovitch, IEEE J. Photovoltaics 4, 175–182 (2014)
- Near-field electromagnetic theory for thin solar cells, A. Niv, M. Gharghi, C. Gladden, O. D. Miller, and X. Zhang, Phys. Rev. Lett. 109, 138701 (2012)