Recent reports on solar modules based on ultrathin microcells, have shown that unique properties such as flexibility and transparency can be obtained from inorganic solar cells. Here, we present ultrathin solar modules that were fabricated using low-cost metallurgical-grade silicon wafers. In order to compensate the diminished cell performance resulting from high impurity level of the starting material and from small physical thicknesses of the microcells, metallic (Ag) nanoparticles that serve as light-concentrating centers were incorporated to the device by block-copolymer lithography. These plasmonic crystals (nanoparticles) have brought improvements in light absorption and quantum efficiency of the device, and we further enhanced these properties by forming nanopillars via reactive ion etching (RIE). Detailed studies of optical properties and performance of the device with varying the nanostructures’ size, together with investigation of stability of the ultrathin metallurgical-grade silicon microcells over time were carried out.