Which boundary condition to be set for simulating array of nanoparticles on solar cell?

    • Abrar820

      Hello, I am trying to simulate arrays of plasmonic nanoparticle on silicon solar cell on FDTD. I learned from Solar cell methodology – Lumerical Support (Solar Cell Methodology) website that simulating just one unit cell is enough. I have some queries arising from this:

      1. Does simulating one unit cell with symmetric-antisymmetric boundary condition mean that FDTD will calculate Solar Generation Rate, Short Circuit Current Density (Jsc) and other electrical parameters by taking all other nanoparticles present in the configuration? Or do I have to use PML boundary condition to see the effect of all nanoparticles on the solar cell? How different is periodic and symmetric-antisymmetric boundary condition?
      2. If I place 5*5 array of nanoparticles spread throughout the solar cell (as show on the picture attached), can I simulate only one unit cell of 5 nanoparticles to see the overall electrical property of the whole solar cell? Or is that going to count/take only those 5 nanoparticles into consideration for calculation Jsc, solar generation rate?
      3. How deep should the fdtd region go into the rectangular solar cell to measure Jsc, solar generation rate as standard?
      4. To see the I-V characteristics and find Voc, fill factor I learned that I need to use Charge. What is the simulation workflow to do that? Please share this information as I am trying to find electrical behavior of solar cell in charge.

      Thank you for your time.

    • Kyle
      Ansys Employee

      If you use periodic boundary conditions the results will be calculated for the simulated unit cell. However, the results in the solar cell workflows are typically normalized to the surface area of the unit cell, so the results will be applicable to the entire solar cell. The symmetric/antisymmetric BCs are used when the geometry and source inside the unit cell is symmetric/antisymmetric. You can use boundary conditions that are both symmetric/antisymmetric and periodic. This page has more information:
      As I mentioned above, you can simulate one unit cell and normalize the results so that they are applicable to the entire structure.
      The FDTD region should extend until either most of the light has been absorbed (for example, the amplitude decreases to around 10^-5), or to the end of the absorbing region, whichever is first.
      This solar cell example has a workflow that includes CHARGE: This one does as well: I think that this example is similar to yours as well:

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