Improved material quality via impurity and defect analysis for enhanced device performance. Collaborative work between Solarex and NREL

This paper reports on a number of specific experiments in which Solarex Corporation and the National Renewable Energy Laboratory (NREL) have collaborated. This work involves the development of cast polycrystalline silicon for use as the substrate for the manufacture of solar cells. Experiments have been conducted to evaluate the improvements in cell efficiency that can be achieved via modified growth conditions, hydrogen passivation, and phosphorous gettering of the cast polycrystalline silicon substrates. NREL performed the hydrogenation and has also assisted in material evaluation using defect mapping, photocurrent mapping, and Fourier Transformed Infrared (FTIR) Spectroscopy. Both hydrogen passivation and phosphorous gettering show promise as cost effective approaches to increasing cell efficiencies.