Solar cell preparation in thin silicon membranes

Solar cells prepared in a thin (≈30 μm) crystalline silicon membrane with a supporting frame allow an evaluation of the potential of c-Si thin film cells on cheap substrates. At the same time, lightweight and more radiation-hard solar cells may have direct applications in space. This paper studies the fabrication process of solar cells in ≈30 μm thick p-Si epitaxial layers, incorporating a p⁺⁺-Si etch-stop/back-surface field layer, using KOH etching. Wax, rubber and silicon nitride were tested as masking materials during the etching. It was found that both wax and silicon nitride could be used as materials for the masking of supporting frames for solar cell thinning up to 30 μm. However, silicon nitride does not reliably protect the frontside structure