Si thin layer growth from metal solutions on single-crystal and cast metallurgical-grade multicrystalline Si substrates

A simple, vertical-dipping, liquid-phase epitaxy (LPE) method for growth of Si layers from Cu/Si solution at temperatures less than 950°C has been shown to be a promising technique for thin crystalline Si photovoltaic (PV) applications. Solar cells with more than 15% AM1 efficiency were fabricated on 5-μm-thick layers grown from Cu/Si solution on (111) Czochralski (CZ) substrates. To extend the application of this technique to low-cost substrates, we grew thin (5-40 μm) Si layers on cast multicrystalline metallurgical-grade (MG) substrates from Cu/Si solution as well as from Al/Si, Al/Cu/Si, Bi/Si, Ga/Cu/Si, and Sn/Si solutions. The conditions of growth, morphology, solvent incorporation characteristics and problems that arise with the use of multicrystalline Si substrates are discussed. A diagnostic solar cell with efficiency equal to 0.42 and open-circuit voltage equal to 0.89 of the values for a single crystal control cell was obtained, without any light-trapping scheme, on a 15-μm-thick layer grown on a MG Si substrate