Plasmonic light trapping in ultrathin single crystal silicon membrane for solar cells application

We report the experimental characterization of a promising light trapping scheme, in ultrathin, mechanically flexible, single crystal silicon membranes that included front surface nanotexturization and a back-sruface array of plasmonic metallic nanoparticles for solar cell applications. Sub-ten micrometer free standing silicon membranes were produced by the chemical etching of silicon wafers. The produced membranes were observed to be mechanically flexible, yet sufficiently sturdy to tolerate the different processing steps during solar cell fabrication. We studied the plasmonic effects of different metallic nanoparticles for optical absorption enhancement on the nanotexturized ultrathin silicon membranes by incorporating them on the back surface of the samples. A promising short circuit current density as high as 36.43 mA/cm² was calculated from the measured optical absorption spectra in a 7.85 μm thick single crystal silicon membrane with front surface nanotexturization along with a back surface array of random mixture of gold and silver nanoparticles. The extracted current density value compares favorably well with the value of 15.68 mA/cm² associated with a flat silicon membrane of the same thickness. The described light trapping scheme may enable the possibility for demonstrating high-efficiency, mechanically flexible photovoltaic devices in the near future.