  Metal halide perovskite nanowires (PrvNWs) have recently emerged as an
interesting path for nanostructured solar cells. Here, we model the absorption
of light in PrvNW arrays for varying diameter and length of the PrvNWs and
period for the array by solving the Maxwell equations. For long enough bare
PrvNW arrays, we find that the optimum diameter is fixed to that which places
the absorption peak from the HE$_{11}$ waveguide mode in the PrvNWs to the
vicinity of the bandgap wavelength. In contrast, when we include a transparent
conductive oxide (TCO) top contact layer, the optimum diameter shifts to a
larger value by 100 nm. The origin of this shift is traced to a reduced
reflection at the interface between the TCO layer and the PrvNW array when the
PrvNW's diameter is larger. Overall, we find that 1500 nm long PrvNWs can reach
90% of the broadband absorption potential, making this system of high interest
for photovoltaics.
