High-Efficiency Cells From Layer Transfer: A First Step Toward Thin-Film/Wafer Hybrid Silicon Technologies

Future low-cost Si photovoltaics shall combine the high-efficiency potential of ultrathin monocrystalline Si films with the low cost per area of the Si-thin-film photovoltaics. The literature describes various techniques for fabricating ultrathin monocrystalline Si films with no need for sawing wafers. Layer transfer using epitaxy on porous Si and subsequent layer separation is one option. We demonstrate an independently confirmed aperture efficiency of 19.1% for a 4-cm²-sized layer transfer cell with a thickness of 43 μm. This cell has a passivated emitter and rear contact structure with an Al₂O₃-surface passivation by atomic layer deposition and lasered contact openings. Highly efficient thin crystalline solar cells have to be integrated into modules. We also report on laser bonding of Si cells to a metalized carrier for module integration.