I know how to calculate the transmission and electric fields for an unpolarized light. However, I wish to calculate the short circuit current density generated in a solar cell of my design for an unpolarized light source. I want to calculate this using both FDTD Solutions and CHARGE (DEVICE). How do i achieve this?
The best starting point is our dedicated page on the knowledge base: https://kb.lumerical.com/en/index.html?solar_cells.html. It includes information about the methodology as well as several examples of optical and electrical simulations.
Regarding unpolarized light, you will need to run 2 simulations with orthogonally polarized sources and then incoherently sum the results as shown at https://kb.lumerical.com/en/index.html?ref_sim_obj_fdtd_coherence_unpolarized_beam.html.