Crystalline silicon is the most used semiconductor material for solar cell applications accounting for more than 90% of the market share. Nowadays, multicrystalline and monocrystalline silicon are mainly produced from directional solidification and Czochralski method, respectively. Solar cells made of these two types of material have shown efficiencies below the theoretical limit due to the presence of impurities in the silicon feedstock, challenges during the solidification process and issues in the different solar cell flowchart steps. This book chapter focuses on the solidification of the silicon photovoltaic value chain and corresponding growth technologies. A detailed description of the directional solidification and Czochralski method apparatus is initially presented. The several types of defects generated during the solidification as well as the source of impurities incorporation into the ingots are described in detail. Among different defects, dislocations and grain boundaries are presented for directional solidification and voids and oxygen-related defects for the Czochralski method. At the end, alternative methods to grow silicon substrates from both liquid and gaseous phase at lower cost and moderate qualities compared to standard processes are presented. These methods are still not considered to be cost-effective compared to more traditional ones due to the higher defect density.
Part of the book: New Research on Silicon