Role and optimization of diffraction gratings for multiresonant light trapping in ultrathin solar cells

We present a study on the role and optimization of diffraction gratings used as back reflector/scatterer in multiresonant GaAs ultrathin solar cells. We show the influence of parameters variation for the grating and for the pattern on the diffraction efficiencies. With an optimized square pattern, we show a record-high absorption of 92.5% in a 100 nm-thick GaAs absorber. Accounting for parasitic absorption, the estimated short-circuit current is 26.4 mA/cm2. We also discuss routes towards even higher currents by breaking the degeneracy of the modes with non-symmetric structures.