15.4%-efficient and 25 μm-thin crystalline Si solar cell from layer transfer using porous silicon

A monocrystalline silicon wafer with a porous Si surface is an ideal seed for the epitaxial growth of thin monocrystalline Si films. After growth, we process a solar cell into the epitaxial film without using costly photolithography. We glue the cell to a glass carrier and separate it from the growth substrate at the porous Si layer. The substrate wafer is re-usable. We achieve an independently confirmed power conversion efficiency of 15.4% with a 25.5 μm-thick cell (3.88 cm2) using layer transfer with porous Si.