Thin-film monocrystalline-silicon solar cells on transparent high-temperature glass-ceramic substrates

Solar modules made from thin-film crystalline-silicon layers of high quality on glass substrates could lower the price of photovoltaic electricity substantially. One possibility is to use polycrystalline-silicon thin films, but the difficulty of this approach is to obtain a sufficiently high material quality and to achieve an effective passivation of the numerous grain boundaries. However, the utilization of a monocrystalline-silicon thin film instead of a polycrystalline-silicon layer should enable simpler device processes, higher process yield and a single-crystal-like efficiency due to the intrinsic higher quality of the material. In this paper, 10-micron thick monocrystalline-silicon layers on transparent glass-ceramic substrates were made by epitaxial thickening of thin monocrystalline-silicon seed layers. By using a very simple cell structure that does not incorporate any light trapping features, silicon single-crystal solar cells on glass-ceramics presented efficiencies of up to 7.5%. However, efficiencies above 9% should be realizable by simply improving the contacting scheme. In addition, by integrating an efficient light trapping scheme and by optimizing the minority carrier diffusion length, the efficiency potential could be as high as 15% for films with a thickness between five to ten microns on glass-ceramics.