  Recently, we studied the effect of hexagonal sinusoidal textures on the
reflective properties of perovskite-silicon tandem solar cells using the finite
element method (FEM). We saw that such nanotextures, applied to the perovskite
top cell, can strongly increase the current density utilization from 91% for
the optimized planar reference to 98% for the best nanotextured device (period
500 nm and peak-to-valley height 500~nm), where 100% refers to the
Tiedje-Yablonovitch limit.
  In this manuscript we elaborate on some numerical details of that work: we
validate an assumption based on the Tiedje-Yablonovitch limit, we present a
convergence study for simulations with the finite-element method, and we
compare different configurations for sinusoidal nanotextures.
