Directional Solidification Spherical Crystallization Front Solar Silicon
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Solution Overview
Problem
The photovoltaic industry faces challenges in producing solar-grade silicon efficiently and cost-effectively due to the high impurity levels in metallurgical silicon, which requires extensive processing steps to meet purity requirements, and the limitations of using waste silicon from the electronics industry are no longer sufficient to meet demand.
Innovation Solution
The method involves directional solidification with a crystallization front shaped like at least one section of a spherical surface, enhancing the cleaning effect by increasing the surface area of the crystallization front, thereby reducing the need for additional processing steps and improving the cost-effectiveness of producing solar-grade silicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional directional solidification with a flat crystallization front is used, then the purification process is simpler, but the cleaning effect is insufficient and multiple processing steps are required
Solution Approach 1:
The patent applies spherical curvature to the crystallization front by using a susceptor with a spherical lower surface. This spherical geometry increases the surface area of the crystallization front compared to conventional flat surfaces, thereby enhancing the segregation effect and improving impurity removal efficiency during directional solidification, reducing the need for multiple processing steps
2Manufacturing precision
If extensive processing steps are applied to metallurgical silicon, then purity requirements are met, but production cost and energy consumption increase
Solution Approach 1:
By implementing a spherical crystallization front through the susceptor design, the patent enhances the purification effect in a single directional solidification step. This reduces the need for repeated melting and solidification cycles or additional chemical cleaning steps, thereby lowering overall energy consumption while achieving the required purity level of solar-grade silicon
3Manufacturing precision
If a flat crystallization front is used in directional solidification, then the process is easier to control, but the cleaning effect is limited
Solution Approach 1:
The spherical lower surface of the susceptor automatically generates a spherical crystallization front during directional solidification. This geometric design simplifies the control mechanism while significantly increasing the crystallization front surface area, thereby enhancing the segregation effect and improving impurity removal without complicating the operational control of the solidification process
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the cost-effective production of solar-grade silicon with reduced impurities, benefiting the production of silicon discs and solar cells by concentrating impurities in the last solidified areas, which can be easily separated, thus minimizing further processing and energy consumption.
Implementation Method 1
the silicon melt solidifies in a directed manner
Implementation Method 2
The so-called segregation effect can therefore be used to clean the silicon material by collecting the impurities in the solidification or crystallization front in front of the solidified silicon and driving them in front of the crystallization front in the case of directional solidification
Data Source
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AI summary
Disclosed is a method for producing silicon that is suitable for solar purposes. Said method comprises the following steps: silicon is fused; and the melt is frozen in a directed manner, a crystallization front that has the shape of at least one sector of a spherical surface being formed during the directed freezing process.