Enhanced light absorption in thin-film silicon solar cells by scattering from embedded dielectric nanoparticles

We investigate the light-trapping effects of dielectric nanoparticles embedded within the active semiconductor layer of a thin-film solar cell. The baseline model consists of a 1.0 μm slab of crystalline silicon on an aluminum back contact topped with a 75 nm Si₃N₄ anti-reflective coating. Using finite-difference time-domain (FDTD) simulations, we calculate the absorption gain due to a periodic array of SiO₂ nanospheres with characteristic depth, diameter, and pitch. Under optimal conditions, spectrally integrated absorption gain due to embedded spheres can reach as high as 23.4 % relative to the baseline geometry. Using a geometry with an Au-core and SiO₂ shell, it is even possible to reach 30% after accounting for Ohmic losses. We also discuss the trade-offs between broadband scattering efficiency, poor absorption at long-wavelengths, and semiconductor displacement due to the embedded nanospheres.