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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 cm 2 ) using layer transfer with porous Si.

We fabricate a 25.5‐μm‐thick monocrystalline Si solar cell with a confirmed power conversion efficiency of 15.4% and an area of 3.88 cm2 using a layer transfer process with porous Si. The process is free of photolithography and contains no high‐temperature oxidation steps. We investigate three design features that improve the short‐circuit current density to a value of 32.7 mA/cm2 under AM1.5 illumination. The detached back reflector contributes 2 mA/cm2, a reduced front‐surface reflectance accounts for an additional 2 mA/cm2 and a reduced base doping increases the current density by 1 mA/cm2. Copyright © 2002 John Wiley & Sons, Ltd.

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