Development of the technology and equipment for low cost solar silicon
The purpose of the present work is the development of the technology and equipment for low cost solar-grade silicon (SGSi) production. The new technology makes it possible to reduce significantly the price for solar-grade silicon (minority carriers' lifetime is 20-30 microseconds, p-type conductivity with the resistance of 35 ohm?cm) up to 5.0 - 8.0 USD per kg .
High cost of silicon limits the rate of solar energy development. Only cheap silicon, produced by special technology, will allow to make solar energy not exotic, but necessary integral part of the world civilization. In fact, existing silicon production technologies, including chloride technology (Siemens - process), are laboratory ones with high expenses, energy costs and low output, which is principally defined by the technology.
The present work is devoted to the creation of the equipment and technology for the production of low cost silicon for solar cell manufacture.
The technology consists of 3 operations: silicon oxide carbothermic reduction, purification of the produced silicon at melting under current flow in transverse magnetic field, and crystallization.
At the first stage of SGSi production it is already possible to obtain silicon, 100-1000 times more pure than MGSi usually has.
The advantage of the purification while current flows in magnetic field is the force action influencing all impurities in the entire metal space, in contrast to crystallization, when impurities removal takes place only in the liquid - solid interface. Therefore, purification while current flows in transverse magnetic field is highly efficient and has high purification level.
The technology developed will allow not only to solve quite serious environ-mental problems in silicon manufacture, but also to correspond the industrial re-quirements of SGSi at a competitive price.
Comparison of the new technology and widely used Siemens process shows the new technology advantages in price, low specific energy consumption of production, principal technological opportunity of high efficiency, low financial expenditure for industrial equipment creation.
The proposed technology and equipment allows to solve the world problem of low cost for solar-grade silicon.