  A design tool was formulated for optimizing the efficiency of inorganic,
thin-film, photovoltaic solar cells. The solar cell can have multiple
semiconductor layers in addition to antireflection coatings, passivation
layers, and buffer layers. The solar cell is backed by a metallic grating which
is periodic along a fixed direction. The rigorous coupled-wave approach is used
to calculate the electron-hole-pair generation rate. The hybridizable
discontinuous Galerkin method is used to solve the drift-diffusion equations
that govern charge-carrier transport in the semiconductor layers. The chief
output is the solar-cell efficiency which is maximized using the differential
evolution algorithm to determine the optimal dimensions and bandgaps of the
semiconductor layers.
