What purity level is required for solar grade silicon?
This question does not have a simple answer. The levels of the various impurities in the Silicon will affect cell performance. Some impurities, such as the metals, will make the Silicon too conductive for the photovoltaic effect. Some impurities can make it difficult to cut wafers. Other impurities, particularly Boron and Phosphorous, function as dopants and must be below threshold levels and be in a specific balance for proper solar cell performance. Depending upon the ingot, or ribbon, growing technique, some impurities can even affect the ability to create the ingot or ribbon. To optimize a solar grade silicon, it is important to address all of these factors and provide a consistent product that optimizes cell cost and performance while providing high production yield throughout the value chain. To provide a solar grade solution, these purity and product factors must be addressed along with the ability of the manufacturing process to scale quickly to allow the industry to keep pace
