Epitaxial thin-film Si solar cells

Most types of thin-film solar cells imply a radical departure from the dominant bulk crystalline Si technology. This is not the case for epitaxial thin-film solar cells. In this technology, a high quality Si layer is deposited epitaxially on a low-cost Si substrate (e.g. cast Upgraded Metallurgical Grade silicon or high-throughput Si ribbons) and processed into a solar cell. This technology combines the well-known advantages of crystalline Si (high efficiency potential, stability and reliability) with a substantial cost reduction potential. Moreover, the similarity to the traditional Si technology lowers the threshold for adoption by the PV industry. This paper gives an overview of the field of epitaxial thin-film solar cells, covering substrates, deposition techniques and solar cell processing. Achievements reported in the literature are summarized and recent results are presented. Special attention is given to the crucial issue of achieving high currents by increasing absorbance in the active layer. This can be achieved by increased absorption through material engineering and through implementation of advanced light confinement schemes. (c) 2005 Elsevier B.V. All rights reserved.