Thin‐film (25.5 μm) solar cells from layer transfer using porous silicon with 32.7 mA/cm2 short‐circuit current density

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.