Plasmonic Nano-Gratings for High-Efficient Ultrathin GaAs Solar Cells

28th European Photovoltaic Solar Energy Conference and Exhibition; 166-169
We propose to integrate 2D plasmonic nano-gratings in ultrathin GaAs solar cells and demonstrate light absorption enhancement on a broad spectral range. We present several geometries fulfilling this goal. First, we describe the multi resonant broadband absorption mechanism achieved in a 25 nm-thick GaAs layer thanks to a metallic nanostructure array. We then describe two novel architectures to trap light inside ultrathin (25 to 110 nm) semiconductor layers. Light trapping in these two designs is based on the use of metallic nanogrids on the front or the back side of the device. Thanks to numerical simulations, we show in both cases an increase in absorption, reaching more than 80% on average on the 550-900 wavelength range for a 25 nm-thick GaAs layer. We calculated a corresponding theoretical short circuit current density of 21.6 mA/cm2. For a 110 nm-thick p-i-n heterojunction complete solar cell design, we achieve a theoretical Jsc of 22 mA/cm2, representing a rise of 23% compared to the device without nanostructures. Along with these simulations, first experimental validation of these light trapping concepts is presented.