Deposition of device-quality amorphous and microcrystalline silicon films with a new "hot wire" CVD technique

For the "Hot Wire" chemical vapor deposition technique (HWCVD) method to be a viable approach for photovoltaic applications, certain critical technical issues need to be addressed and resolved such as filament lifetime, reproducibility, and the ability to scale the technique to large area substrates. We have developed a new approach (patent applied for) that addresses some of these problems, specifically longevity of the filaments and reproducibility of the materials produced. The new filament material used has so far shown no appreciable degradation even after deposition of 500 pm of amorphous silicon (a-Si). We report that this technique can produce "state-of-the-art" a-Si and that a solar cell of p/i/n configuration exhibited an initial efficiency approaching 9%. The development of microcrystalline silicon materials and devices is also discussed, and we report on large area materials development (30 cm X 30 cm) using this technique.