Angled Plasma Torch Silicon Purification
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Solution Overview
Problem
Current silicon purification methods for solar cells face inefficiencies in removing boron and other impurities, particularly due to limitations in the contact area between plasma gas and silicon melt surface, which affects the purification efficiency.
Innovation Solution
A silicon purification method and device that injects plasma gas at an angle of 20° to 80° to the silicon melt surface, forming elliptical recesses and promoting circulation flow, with multiple plasma torches arranged to increase contact area and maintain a radical-rich plasma zone, enhancing impurity removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If plasma gas is sprayed vertically onto the silicon melt surface, then heating efficiency is improved, but the contact area between plasma gas and melt surface is reduced
Solution Approach 1:
The plasma torch is positioned at an angle of 20° to 80° relative to the melt surface rather than vertically, creating a dynamic spray pattern that increases contact area while maintaining heating efficiency through controlled plasma gas flow direction
Solution Approach 2:
The plasma gas spray is directed at an angular dimension rather than perpendicular to the surface, transforming the contact geometry from a point/line contact to a broader area contact across the melt surface
2Productivity
If multiple plasma torches are used to increase contact area, then purification efficiency is improved, but device complexity increases
Solution Approach 1:
The purification process is divided into multiple zones by using several plasma torches positioned at different locations around the crucible, allowing simultaneous treatment of different melt surface areas and improving overall purification efficiency
Solution Approach 2:
Multiple plasma torches are combined in a coordinated arrangement where each torch contributes to the overall purification process, merging their individual effects to achieve enhanced impurity removal while maintaining manageable system complexity
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
The method significantly improves silicon purification efficiency by increasing the contact area between plasma gas and silicon melt, leading to effective oxidation and removal of impurities, resulting in higher purity silicon with reduced boron concentrations.
Implementation Method 1
oxidative purification is performed to remove boron (B) or contained impurities through heating by plasma arc or plasma gas
Implementation Method 2
The plasma arc is generated by applying a direct current through both electrodes in the plasma torch. The generated plasma arc is injected from the nozzle port, which also serves as the anode electrode, of the plasma torch toward the silicon metal loaded in the crucible, thereby heating the silicon metal
Data Source
AI summary
The silicon purification method uses a silicon purification device including at least a crucible for loading a silicon metal and a plasma torch, and purifies the silicon metal by injecting a plasma gas from the plasma torch toward a melt surface of the silicon metal loaded in the crucible in a state where an angle formed by the melt surface and the plasma gas is set in the range of 20° to 80°.