Thin-film crystalline silicon mini-modules using porous Si for layer transfer

Layer transfer processes yield Si films of high electronic quality on low-cost non-Si carriers such as glass: a crystalline Si film grows on a Si-substrate wafer, is detached from that substrate and transferred to a low-cost non-Si device carrier. The substrate wafer is re-used for further growth cycles. Electrochemical etching of a porous Si (PSI) layer system into the substrate wafer enables homoepitaxial growth of monocrystalline Si films and facilitates the detachment of the film. We discuss the potential of crystalline thin-film cells from layer transfer and review the layer transfer work conducted at ZAE Bayern. The sevenfold use of a substrate wafer and the transfer of a 10 x 10cm(2) epitaxial film from a 6"-wafer is demonstrated. A new module process that permits an integrated series connection by a single metallization step is demonstrated to yield a module efficiency of 10%. (C) 2004 Elsevier Ltd. All rights reserved.