High efficiency ultra-thin silicon photonic crystal based solar cells

In this work, we present a comparative theoretical study about the optical absorption coefficient calculated in ordered nanopillar and nanohole photonic crystal silicon structures for solar energy applications. In particular, we investigate the ultimate efficiency at normal incidence condition of such structures for several fill factors and lattice constants. We find that, except for small ranges of frequency where an inversion of tendency is observed, the total absorption coefficient in nanopillar arrays is greater than the one calculated in nanohole arrays. Moreover, optimized silicon nanopillar arrays show percentage improvements of the ultimate efficiency up to 138% with respect to the case of a silicon thin film of equivalent thickness. Finally, we report preliminary experimental results about the realization of a silicon photonic crystal with a nanopillar array structure to be exploited as an optical trapping film in solar cells. © 2013 SPIE.