High efficiency thin upgraded metallurgical-grade silicon solar cells on flexible substrates.

We present a thin film (<20 μm) solar cell based on upgraded metallurgical-grade polycrystalline Si that utilizes silver nanoparticles atop silicon nanopillars created by block copolymer nanolithography to enhance light absorption and increase cell efficiency η > 8%. In addition, the solar cells are flexible and semitransparent so as to reduce balance of systems costs and open new applications for conformable solar cell arrays on a variety of surfaces. Detailed studies on the optical and electrical properties of the resulting solar cells suggest that both antireflective and light-trapping mechanisms are key to the enhanced efficiency.