SBIR PHASE II: Novel Microcrystalline Silicon Solar Cell Devices Prepared Using a Unique Microwave Gas Jet Deposition Technique

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This Small Business Innovation Research (SBIR) Phase II will further develop a novel microwave Gas Jet technique for its use the production of high efficiency microciystalline silicon solar cells at high deposition rates. In Phase I, it was demonstrated technique can he used to prepare microcrystalline silicon i-layers for single-junction nip solar cells at deposition A/s, rate 3-5 times high than those obtained using standard techniques. These rates make the large-scale production microcrystalline cells economically feasible. Microcrystalline cells are an attractive alternative to amorphous silicon germanium cells as red light absorbing structures in high efficiency amorphous silicon based multi-junction solar cell devices because their efficiencies do not degrade with long-term light exposure. Thus use of the microcyrstalline materials will lead to higher stable efficiencies for the multi-junction cells. In Phase II, the solar cell efficiencies for these microcrystalline cells will be further improved through optimization of the deposition conditions which include the use of carbon and fluorine based gases, and use of new load-locked hardware for the preparation of doped layers without air exposure of layer interfaces. Also, hardware designs for large-scale usage of the Gas Jet technique will be tested. A successful program will lead to the replacement of the standard rf glow discharge deposition technique in ECD's joint venture solar module production lines with the Gas Jet technique as well as the replacement or red-light absorbing amorphous silicongermanium layers in ECD's triple-junction solar cell design with more stable microcrystalline layers. As a result, we will fabricate modules with higher stable efficiencies at reduced costs. This will lead to a wider use of Photovoltaic (PV) products thereby reducing the dependency on fossil fuel energy sources. Development of a high deposition rate technique to prepare high quality microcrystallitic silicon could also be used in other applications such as in thin film transistors, photodetectors, and photosensors.