Gas Jet Meniscus Stabilization for Silicon Sheet Extraction
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Solution Overview
Problem
Current methods for producing silicon sheets from a melt, such as the Czochralski method and vertical ribbon pulling, face challenges like material waste, temperature gradients leading to poor crystal quality, and difficulties in initiating and controlling the pulling process, which hinder the production of high-quality, thin silicon solar cells.
Innovation Solution
A method and apparatus using gas impingement to stabilize the meniscus and control the pressure distribution, allowing for horizontal sheet formation from a melt without kerf loss, with the gas jets maintaining a stable meniscus and enabling continuous sheet extraction without external stress, thus improving crystal quality and reducing material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If gas jets are used to stabilize the meniscus and enable horizontal sheet formation from a melt, then material waste is eliminated and crystal quality is improved, but the device complexity increases due to the need for gas jet apparatus and pressure control systems
Solution Approach 1:
The patent applies pneumatic principles by using gas jets to stabilize the meniscus of the melt during horizontal sheet formation. Gas is introduced through jets positioned near the meniscus to control its stability and position, enabling continuous sheet extraction without the need for physical contact or complex mechanical pulling apparatus. This pneumatic approach eliminates kerf loss associated with sawing while maintaining simple overall process geometry.
2Productivity
If vertical ribbon pulling is used to produce silicon sheets, then production speed can be increased, but temperature gradients cause poor crystal quality and multi-grain silicon formation
Solution Approach 1:
The patent transitions from vertical ribbon pulling to horizontal sheet formation by changing the dimension of sheet extraction. The sheet is formed horizontally from the melt surface and extracted in the horizontal direction, eliminating the vertical temperature gradient that causes crystal defects. This dimensional change allows faster production speeds while maintaining single-crystal quality throughout the sheet.
3Ease of operation
If low angle pulling is used to prevent melt spilling, then sheet extraction is controlled, but the process is difficult to initiate and control due to meniscus stability issues
Solution Approach 1:
The patent introduces gas as an intermediary substance to mediate the interaction between the melt meniscus and the extraction process. Gas jets are positioned to interact with the meniscus, providing stabilizing pressure and control without requiring precise mechanical positioning or low-angle geometry. This intermediary gas phase simplifies process initiation and control while ensuring meniscus stability throughout extraction.
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 enables the production of high-quality silicon sheets with reduced material waste and improved crystal quality, facilitating the wider adoption of solar cells by lowering production costs and enhancing the efficiency of solar cells.
Implementation Method 1
Gas jets may be used to stabilize the meniscus or provide a pressure distribution that prevents the melt from spilling
Implementation Method 2
The removed latent heat during cooling and solidifying of the silicon must be removed along the vertical ribbon
Implementation Method 3
allow the pulled silicon to cool and solidify into a sheet
Implementation Method 4
The angle, surface tension, and melt level are balanced to prevent the melt from spilling over the crucible
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
In one embodiment, a sheet production apparatus comprises a vessel configured to hold a melt of a material. A cooling plate is disposed proximate the melt and is configured to form a sheet of the material on the melt. A first gas jet is configured to direct a gas toward an edge of the vessel. A sheet of a material is translated horizontally on a surface of the melt and the sheet is removed from the melt. The first gas jet may be directed at the meniscus and may stabilize this meniscus or increase local pressure within the meniscus.