Solar Cell Interconnect Foil With Local Yield Strength Control
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Solution Overview
Problem
Interconnecting solar cells is challenging due to issues like ratcheting and wafer bowing, which reduce the reliability and lifetime of solar cells and modules, primarily caused by thermal stress mismatch between silicon and metal materials.
Innovation Solution
The use of conductive foil with varying yield strengths for forming interconnect structures, where the foil over the solar cell has a lower yield strength to inhibit wafer bowing and the interconnect structure has a higher yield strength to prevent ratcheting, achieved through techniques like dual tempering and strategic placement of additional materials for stress relief.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform yield strength conductive foil is used for interconnection, then manufacturing is simple, but both wafer bowing and ratcheting occur reducing reliability
Solution Approach 1:
The conductive foil is designed with spatially varying yield strength: the first portion (over the solar cell) has lower yield strength to accommodate thermal expansion and prevent wafer bowing, while the second portion (interconnect structure) has higher yield strength to prevent ratcheting. This local differentiation of material properties resolves the contradiction by addressing different functional requirements in different locations.
Solution Approach 2:
The conductive foil is segmented into distinct portions with different yield strengths. The first portion extends over the solar cell surface while the second portion forms the interconnect structure, with an interface between them. This segmentation allows each portion to be optimized for its specific function, improving overall reliability without requiring completely separate components.
2Reliability
If high yield strength material is used for interconnect structure, then ratcheting is prevented, but wafer bowing occurs reducing lifetime
Solution Approach 1:
The conductive foil is designed with spatially varying yield strength: the first portion (over the solar cell) has lower yield strength to accommodate thermal expansion and prevent wafer bowing, while the second portion (interconnect structure) has higher yield strength to prevent ratcheting. This local differentiation of material properties resolves the contradiction by addressing different functional requirements in different locations.
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 the reliability and performance of solar cells and modules by reducing ratcheting and wafer bowing, leading to improved lifetime and efficiency in solar cell interconnections.
Implementation Method 1
thermal stress mismatch between silicon and metal materials
Implementation Method 2
conductive foil with varying yield strengths for forming interconnect structures, where the foil over the solar cell has a lower yield strength to inhibit wafer bowing and the interconnect structure has a higher yield strength to prevent ratcheting
Data Source
AI summary
A solar cell can include a conductive foil having a first portion with a first yield strength coupled to a semiconductor region of the solar cell. The solar cell can be interconnected with another solar cell via an interconnect structure that includes a second portion of the conductive foil, with the interconnect structure having a second yield strength greater than the first yield strength.