Photonics

Photonics

Solar Cell Source Polarization in Different Structures

    • spacelover17
      Subscriber

      I was a bit confused about the proper calculation for solar cells in different structures. In the TiO2 pyramid array example, it mentions that the symmetry of the problem allows us to only use one polarization, although "some care is required to calculate the unpolarized response correctly". However, the example files seem to show nothing special being done to calculate the unpolarized response. The planar example here only refers to polarization sensitivity in the abstract, so I'm assuming it's not important here. The 3D pillar example here does actually run two different polarizations but doesn't do anything with it in FDTD, only in charge.

      So going back to the TiO2 pyramid example, what "care" is required to calculate the unpolarized response for this particular 3D structure?

    • Taylor Robertson
      Ansys Employee
      Hey In the Ti02 and planar cell there is more symmetry. For the planar structure any polarization is equivalent, and the pyramid has 4-fold rotation so X, and Y polarizations are equivalent. At normal incidence this reduces to a single simulation, since the results from the simulations would be equal. In general you need to add the contributions of two orthogonal polarization for each plane incidence angle. Even for the pyramids if you were to inject light at an incidence angle then the symmetry is broken, and you need to consider two orthogonal polarizations. Likewise if you were to make the unit cell rectangular then the symmetry is broken and you need to consider two polarizations even at normal incidence. When using dipole sources you would need three. Take a look at the following article for more rigorous illustration https://support.lumerical.com/hc/en-us/articles/1500006149562-Polarization-incoherence

      Best
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