Silicon Substrate Copper Removal via Charged Insulation Layer
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Solution Overview
Problem
Silicon solar cells suffer from light-induced minority-carrier lifetime degradation due to copper impurities, which reduces efficiency and is challenging to address in multicrystalline and single crystalline silicon substrates.
Innovation Solution
A method involving a charged insulation layer on the silicon substrate to generate a potential difference, allowing impurities like copper to diffuse into the boundary between the substrate and the insulation layer through heat treatment, thereby reducing excess carrier-induced degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If copper impurities are present in silicon substrate, then solar cell manufacturing cost is reduced, but light-induced minority-carrier lifetime degradation occurs reducing efficiency
Solution Approach 1:
The patent extracts copper impurities from the bulk silicon substrate by creating a charged insulation layer that generates an electric field. This field drives copper atoms to diffuse toward the insulation layer boundary, effectively removing them from the active solar cell region where they would cause light-induced degradation.
Solution Approach 2:
The charged insulation layer acts as an intermediary structure between the silicon substrate and the external environment. It generates an electric field that mediates the movement of copper impurities, concentrating them at the interface without requiring direct contact with external removal mechanisms.
2Manufacturing precision
If traditional high-temperature heat treatment is used to remove impurities, then impurity removal effectiveness is improved, but manufacturing complexity and energy consumption increase
Solution Approach 1:
The patent changes the key parameter from temperature-driven diffusion to electric field-driven diffusion. By applying a charge to the insulation layer, copper impurities are driven to the boundary at lower temperatures, eliminating the need for complex high-temperature heat treatment processes while maintaining effective impurity removal.
Solution Approach 2:
The patent replaces thermal energy (heat treatment) with electrical energy (charged insulation layer) as the driving force for impurity migration. This substitution simplifies the manufacturing process by avoiding high-temperature equipment and complex thermal management systems.
3Reliability
If copper concentration is reduced in silicon substrate, then light-induced degradation is decreased, but manufacturing cost increases
Solution Approach 1:
The patent applies local quality by creating a charged insulation layer only at specific regions of the silicon substrate where impurity concentration needs to be reduced. This localized treatment allows copper removal from critical areas while maintaining cost-effective bulk material usage, rather than requiring uniform high-purity silicon throughout.
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 method effectively improves the performance and efficiency of silicon substrates by deactivating copper impurities, enhancing the stability of solar cells without requiring a complete solar cell structure or high-temperature processes, and can be performed at room temperature.
Implementation Method 1
heat treating the silicon substrate for enabling at least one impurity causing the excess carrier induced degradation and being in the silicon substrate to diffuse due to the potential difference into a boundary of the silicon substrate and the insulation layer
Implementation Method 2
Light activation of the interstitial copper reduces an electrostatic repulsion between positively charged interstitial copper ions and copper precipitates, which enables copper to precipitate in the wafer bulk
Data Source
Figure 1
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AI summary
An embodiment of the invention relates to a method for decreasing an excess carrier induced degradation in a silicon substrate (310), the method comprises providing a charged insulation layer (320) capable of retaining charge on the silicon substrate (310) for generating a potential difference between the charged insulation layer (320) and the silicon substrate (310), and heat treating the silicon substrate (310) for enabling an impurity causing the excess carrier induced degradation and being in the silicon substrate (310) to diffuse due to the potential difference into a boundary (330) of the silicon substrate (310) and the insulation layer (320).