ECN publication
Final Report MissionN & Miracle : Micro Crystalline Silicon in the Netherlands
Soppe, W.J.; Devilee, C.; Biebericher, A.C.W.; Smit, C.; Swaaij, R.A.C.M.M. van; Houston, I.; Sanden, M.C.M. van de; Gordijn, A.; Rath, J.K.; Schropp, R.E.I.; Donker, H.; Goossens, A.
Published by: Publication date:
ECN Solar Energy 1-1-2004
ECN report number: Document type:
ECN-C--04-009 ECN publication
Number of pages: Full text:
100 Download PDF  


This report summarizes results obtained in the projects MissionN and Miracle, on the development of new deposition methods for microcrystalline silicon (mc-Si). The research has been carried out on five different locations in the Netherlands: TU-Eindhoven, Dimes-Delft, TAC-Delft, Utrecht University and ECN. Two new deposition methods for growth of intrinsic mc-Si layers for solar cell applications have been investigated: Expanding Thermal Plasma (ETP) and Microwave Plasma Enhanced Chemical Vapour Deposition MWPECVD. For both methods it is shown that fast growth (> 1 nm/s) of mc-Si is possible. In this project however, it has been found that these high growth rates are accompanied with high porosity of the layers. As a result the required electronic quality of mc-Si for solar cell application has not been obtained yet. Efficiencies of cells with i-layers deposited by one of these methods did not meet the project aim of 8% but were limited to 1.9 % and 0.5 % for respectively ETP and MWPECVD. Cells made with MWPECVD grown i-layers suffered extra from post oxidation resulting from vacuum interruption since different layers of these cells had to be manufactured at different locations.

A new and more effective method for deposition of doped mc-Si layers was developed successfully: the Layer-by-Layer method. With this method doped layers can be made in a wide temperature regime (150 - 400 °C), with a much higher doping efficiency than by the conventional continuous deposition method.

Research on the growth mechanisms of mc-Si by ATR-FTIR and spectral ellipsometry has shown that deposition of mc-Si always starts with an amorphous incubation layer (even when a crystalline Si wafer is used as substrate). The amorphous incubation layer continues into an a-Si/mc-Si mixed layers and then continues into an almost full crystalline mc-Si layer. Thicknesses of incubation and mixed layer can be controlled by the ratio of SiH4 and H2. The substrate temperature has little or no effect on the final crystal fraction of the layer.

Work on development of new and advanced characterization tools for mc-Si has yielded some promising methods: (Transient Absorption Spectroscopy and Time of Flight measurements) which will be applied in future for analysis of mc-Si.

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