Absorption Enhancement for Ultrathin Solar Fuel Devices with Plasmonic Gratings

We present a concept for an ultrathin solar fuel device with a nanostructured back contact. Using rigorous simulations, we show that the nanostructuring significantly increases the absorption in the semiconductor, CuBi2O4 in this case, by 47 5.2 mA cm 2 through the excitation of plasmonic modes. We are able to attribute the resonances in the device to metal insulator metal plasmons coupled to either localized surface plasmon resonances or surface plasmon polaritons. Rounding applied to the metallic corners leads to a blue shift in the resonance wavelength while maintaining absorption enhancement, thus supporting the possibility for a successful realization of the device. For a 2D array, the tolerance of the polarization dependent absorption enhancement is investigated and compared to a planar structure. The device maintains an absorption enhancement up to incident angles of 75 . The study highlights the high potential for plasmonics in ultrathin optoelectronic devices such as in solar fuel generatio