Eutectic Interlayer Bonding for Photovoltaic Device Coverglass
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Solution Overview
Problem
Conventional bonding technologies for photovoltaic devices, particularly for inverted metamorphic solar cells, face challenges such as mechanical fragility, cracking, and contamination issues when using silicone-based adhesives, which transfer deleterious forces and are prone to degradation under space conditions.
Innovation Solution
The use of a eutectic interlayer that bonds photovoltaic cells to a transparent covering, such as coverglass, with a melting temperature increased by bonding with the covering material, allowing for isothermal solidification and forming a thin, resilient bond without residual stresses, and suppressing contamination and degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional silicone-based adhesives are used to bond solar cells to coverglass, then the bonding process is simple and flexible, but deleterious forces are transferred to the fragile solar cells causing cracking and mechanical failure
Solution Approach 1:
A thin interlayer of eutectic material is introduced between the solar cell and coverglass. This interlayer has a melting point below the solar cell's damage threshold, allowing it to temporarily become liquid during bonding, wet the surfaces, and then solidify to form a strong mechanical interlock. This intermediary layer absorbs bonding stresses and prevents direct force transfer to the fragile solar cell, eliminating cracking while maintaining bonding effectiveness.
2Strength
If rigid panel structures are used for solar arrays, then structural support is provided during launch and orbital operation, but thermal mismatch strains develop causing cracks in the solar cells
Solution Approach 1:
The eutectic interlayer undergoes a phase change from solid to liquid at a controlled temperature below the solar cell damage threshold. During the liquid state, it accommodates thermal expansion differences between the rigid coverglass and solar cell. Upon cooling, it solidifies to provide mechanical support. This parameter change allows the system to maintain structural integrity while accommodating thermal mismatches that would otherwise cause cracking.
3Strength
If thin eutectic interlayer is used to bond solar cell to coverglass, then a strong mechanical bond is formed, but contamination may occur during the bonding process
Solution Approach 1:
The bonding process utilizing the eutectic interlayer is conducted in a controlled inert atmosphere or vacuum environment. This prevents oxidation and contamination of the eutectic material during heating and bonding. The inert environment protects the molten eutectic layer from reacting with atmospheric gases, ensuring a clean, contamination-free bond between the solar cell and coverglass while maintaining the desired mechanical strength.
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 solution enhances the mechanical stiffness and resistance to thermal cycling of photovoltaic devices, reduces the risk of cracking, and maintains optical properties, while being resistant to UV exposure and radiation, thus improving the efficiency and durability of solar arrays.
Implementation Method 1
heating the eutectic layer to a sufficiently high temperature to transition to a liquid state. The liquid eutectic interlayer wets a surface of the solar cell
Implementation Method 2
The liquid eutectic interlayer wets a surface of the solar cell, covering surface components of the solar cell
Implementation Method 3
At least some of a compound of the eutectic interlayer bonds with the transparent covering, raising the melting temperature of the eutectic interlayer above the melting temperature with the full amount of the compound present
Implementation Method 4
increasing a concentration of a gas in the process chamber that causes the eutectic layer to transition into a liquid state
Data Source
AI summary
A solar energy collection system includes a solar cell, a transparent covering, and a eutectic interlayer binding the solar cell and the transparent covering together. At least some of a compound of the eutectic interlayer bonds with the transparent covering, raising the melting temperature of the eutectic interlayer above the melting temperature with the full amount of the compound present.