Processes for Production of Solar‐Grade Silicon Using Hydrogen Reduction and/or Thermal Decomposition

Abstract

AbstractHigh‐purity Si used for photovoltaic applications, namely, solar‐grade Si (SOG‐Si), is commercially manufactured using the Siemens process. Although the present levels of supply satisfy the demand, there can potentially be a shortage of SOG‐Si in the long term. To overcome the low productivity of the Siemens process, various types of SOG‐Si production/purification processes have been developed as post‐Siemens processes. Some processes are under development as new commercial processes. These processes can be classified into the following three categories: (1) hydrogen reduction and/or thermal decomposition of silane‐based gases in improved Siemens‐based processes, (2) metallothermic reduction of silicon halides by Zn or Al, and (3) upgrading metallurgical‐grade Si by employing metallurgical purification methods. This paper presents a review of various types of SOG‐Si production processes, particularly those based on the hydrogen reduction and/or thermal decomposition of halides and silane‐based gases. These processes are classified on the basis of Si compounds used and the reaction types; further, the features of these processes are also analyzed. Future prospects for the development of new high‐purity Si production process are also presented.