Continuous Casting Silicon Substrate Apparatus for Solar Cells
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Solution Overview
Problem
Conventional methods for manufacturing silicon substrates for solar cells result in significant Kerf-loss during cutting processes, increasing costs and compromising both productivity and energy conversion efficiency due to impurity segregation and low crystal grain size.
Innovation Solution
An apparatus and method utilizing continuous casting with a crucible unit, heating unit, casting unit, cooling unit, and transfer unit to control temperature and solidification, maintaining a horizontal solid/liquid interface and perpendicular crystal growth direction, facilitating large crystal grain formation and rapid cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional cutting processes (cropping, grinding, slicing) are used to manufacture silicon substrates from single crystalline silicon ingots or polycrystalline silicon blocks, then silicon substrates can be produced, but significant Kerf-loss occurs (40-50% material loss), increasing manufacturing costs
Solution Approach 1:
The invention extracts and eliminates the unnecessary intermediate steps of ingot/block preparation and cutting processes. By directly casting silicon substrates from molten silicon using continuous casting, the method removes the kerf-loss generating steps while retaining the essential function of substrate production.
Solution Approach 2:
The continuous casting process enables uninterrupted direct formation of silicon substrates from molten silicon. The continuous movement of the substrate through the casting zone eliminates discontinuous cutting operations, maintaining continuous useful action from molten silicon to finished substrate without material loss.
2Productivity
If rapid cooling is applied to increase productivity in direct silicon substrate manufacturing, then production speed improves, but impurity segregation and low crystal grain size occur, reducing energy conversion efficiency
Solution Approach 1:
The invention dynamically adjusts the cooling rate during the solidification process. By controlling the temperature gradient and solidification speed in different zones, the process achieves both rapid solidification for productivity and controlled cooling for crystal quality, preventing impurity segregation and ensuring large crystal grain formation.
Solution Approach 2:
The process changes thermal parameters (temperature, cooling rate, temperature gradient) during solidification to optimize both productivity and crystal quality. By adjusting these parameters, the method achieves rapid solidification without the harmful effects of uncontrolled fast cooling.
3Manufacturing precision
If multiple cutting and processing steps are used to prepare silicon substrates, then substrate quality can be improved through defect removal, but manufacturing complexity and time increase significantly
Solution Approach 1:
The continuous casting process performs preliminary quality assurance during the solidification itself. By controlling the solidification conditions to prevent defect formation in the first place, the method eliminates the need for subsequent defect removal steps, reducing process complexity while maintaining substrate quality.
Solution Approach 2:
The invention applies different cooling rates and temperature gradients to different zones of the substrate during solidification. This local control of solidification conditions ensures high crystal quality in critical areas while maintaining overall process efficiency, reducing the need for additional processing steps.
4Ease of manufacture
If conventional ingot preparation and cutting methods are used, then substrate manufacturing can proceed, but manufacturing time and costs increase due to multiple sequential processes
Solution Approach 1:
The invention merges the molten silicon discharge, casting, and substrate formation operations into a single continuous process. By combining these previously separate steps into one integrated continuous casting operation, the method dramatically reduces manufacturing cycle time while maintaining substrate production capability.
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 enhances productivity and quality of silicon substrates, achieving high energy conversion efficiency while reducing manufacturing costs by minimizing impurity segregation and residual stress.
Implementation Method 1
a heating unit provided to an outer wall and an external bottom surface of the crucible unit and heating the crucible unit to melt the raw silicon
Implementation Method 2
a cooling unit rapidly cooling the cast silicon substrate
Implementation Method 3
solidifying molten silicon to prepare a single crystalline silicon ingot or polycrystalline silicon block
Data Source
AI summary
The present disclosure provides an apparatus for manufacturing a silicon substrate for solar cells using continuous casting, which can improve quality, productivity and energy conversion efficiency of the silicon substrate. The apparatus includes a crucible unit configured to receive raw silicon and having a discharge port, a heating unit provided to an outer wall and an external bottom surface of the crucible unit and heating the crucible unit to form molten silicon, a casting unit casting the molten silicon into a silicon substrate, a cooling unit rapidly cooling the silicon substrate, and a transfer unit disposed at one end of the cooling unit and transferring the silicon substrate. The casting unit includes a casting unit body having a casting space defined therein to be horizontally connected to the discharge port, and an assistant heating mechanism that preheats the casting unit body to control a solidification temperature of the silicon substrate.