Crystalline Silicon Thin Film and Nanowire Solar Cells

Abstract

This chapter reviews recent developments in the field of large grain size crystalline silicon thin film and silicon nanowire solar cells. Both technologies offer considerable potential for photovoltaics if they can be realised with adequate material quality on cheap substrates such as glass. The main methods for forming thin polycrystalline silicon (poly-Si) films on glass are described. These include thermal solid phase crystallisation, liquid phase crystallisation and epitaxial thickening of crystalline seed layers. The corresponding progress made in device technology is outlined. Some recent work on poly-Si film and solar cell formation on higher temperature substrates is also discussed, together with progress on thin monocrystalline layers produced by epitaxy or lift-off from Si wafers. Plasmonic enhancement of solar cells has attracted considerable interest in recent years. An account is given of developments relating to thin crystalline Si solar cells. Finally, the progress made in the fabrication of Si nanowires and microwires, and their deployment in photovoltaic devices is discussed. Both bottom–up and top–down methods of wire formation are considered. Considerable progress has been made in both planar and wire cell technologies, though the latter is at an earlier stage of development and significant research challenges remain for both. However, with further improvements in material quality and light trapping, excellent prospects exist for a cost-effective thin film crystalline Si technology exceeding 15% efficiency. This will offer all the advantages of Si including stability, non-toxicity and high abundance.