Innovative lift‐off solar cell made of monocrystalline‐silicon thin film by annealing of ordered macropores

To answer the challenge of obtaining thinner silicon solar cells, we developed a technique based on the transfer of a thin layer of high‐quality monocrystalline silicon to a foreign low‐cost substrate. The transfer is enabled by the reorganisation of macroporous silicon at high temperature: driven by the minimisation of their surface energy, pores close and, in specific situations, merge to form a large single void, a few micrometers under the wafer surface. As demonstrated in this paper, the micron‐thick film above it may be detached and used to process a solar cell. The difficulty of this approach lies in appropriately ordering the macropores, while its originality is to enable processing of a high‐quality material directly from porous silicon. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)