Crystalline silicon thin-film (cSiTF) solar cells are an attractive alternative to bulk silicon solar cells. At Fraunhofer ISE we follow the concept of the epitaxial wafer equivalent (EpiWE), where 20 mm of silicon are deposited epitaxially by high temperature atmospheric pressure CVD (APCVD) on a cheap silicon substrate. The EpiWE can then be processed using standard industrial cell production. Furthermore, it is possible to simplify the solar cell process when depositing the emitter by epitaxy in-situ after the growth of the base. The epitaxial emitter could be an alternative method of n-type emitter processing with adjustable emitter profile and short deposition time. This paper presents results of cSiTF solar cells with epitaxial emitters and photolithographic contacts, which prove the good performance of the emitter and the applicability of the EpiWE to conventional solar cell processes. Included in the discussion is a description of the CVD deposition principle developed at Fraunhofer ISE and the applied clean room solar cell process. The emitter doping profiles and concentrations, as well as the structural quality, are discussed in detail using SIMS and SEM data. The phosphorus out-diffusion during cooling is prevented by cooling the samples in a PH 3 /H 2 atmosphere. Moreover, a double-layer emitter is formed having blue sensitive properties. The internal quantum efficiencies (IQEs) show that the emitter can be passivated as well as a 'standard' emitter formed by POCl 3 diffusion. Efficiencies up to 14Á9 and 13Á6% for large area cSiTF solar cells on highly doped Cz and mc, respectively, are presented.

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This paper suggests epitaxy of silicon for emitter formation by high temperature CVD as an alternative to conventional processing for standard silicon wafer solar cells. Epitaxy could provide an alternative method to create an adjustable emitter shape at a short deposition time. Results of solar cells of phosphorous-doped epitaxial layers on p-type silicon wafers are presented. Different measurement methods characterising the doping profile and level were applied to such emitters. Until now no standard diffusion process has been found to create boron-doped emitters for n-type silicon wafers. Epitaxially deposited p-type emitters might open the market for n-type crystalline silicon solar cells. This paper presents preliminary and promising results of n-type solar cells with a boron-doped epitaxial emitter.

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