Conductive Paste Penetrating Insulating Films for Solar Cell Contacts
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Solution Overview
Problem
Conventional solar cell structures face challenges in achieving improved electrical performance due to limitations in the composition and methods used for forming solar cells, particularly in the formation of effective electrical contacts on the front side of silicon semiconductor devices.
Innovation Solution
A thick film composition comprising electrically conductive silver, flux materials, and an organic medium is applied to the front side of a solar cell, where the silver and flux materials penetrate insulating films upon firing, forming a conductive path and enhancing electrical contact with the semiconductor substrate, with optional additives like metal oxides to improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metallization methods are used for front-side contacts, then the manufacturing process is simple, but the electrical performance is insufficient
Solution Approach 1:
The patent employs a composite paste composition containing silver particles (30-80 wt%), glass frit (10-40 wt%), and organic vehicle (10-40 wt%). The glass frit component penetrates the insulating film to create electrical contact, while silver provides conductivity. This composite approach resolves the contradiction by achieving superior electrical performance through material composition rather than process simplification.
Solution Approach 2:
The patent modifies the chemical and physical parameters of the contact material by incorporating flux materials with specific softening points and compositions. The glass frit undergoes phase change during firing to enable penetration through the insulating film. These parameter changes allow the material to transition from a non-penetrating state to an electrically conductive state, improving electrical performance while managing composition complexity.
2Reliability
If the thick film composition penetrates the insulating film effectively, then electrical contact is improved, but the insulating film integrity is compromised
Solution Approach 1:
The glass frit in the paste composition exhibits local quality changes during firing - remaining intact in areas where insulation is needed while penetrating through specific regions where electrical contact is required. This localized penetration behavior allows the insulating film to maintain its integrity in most areas while providing effective electrical contact pathways at contact points, resolving the contradiction between contact quality and film integrity.
3Ease of operation
If organic medium is used for paste application, then ease of application is improved, but organic residue after firing becomes a harmful factor
Solution Approach 1:
The organic vehicle in the paste composition undergoes complete decomposition and volatilization during the firing process at temperatures typically between 700-900°C. This parameter change transforms the organic medium from a beneficial application aid into a harmless byproduct that is completely removed, eliminating carbonization and residue issues. The controlled thermal processing ensures complete organic matter elimination while maintaining the beneficial functional properties of the inorganic components.
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
The solution results in improved electrical performance and efficiency of solar cells by forming a robust and efficient electrical contact between the conductive silver and the semiconductor substrate, enhancing the overall performance of the solar cell devices.
Implementation Method 1
upon firing, the organic vehicle is removed and sinters the silver and flux materials
Implementation Method 2
upon firing, the organic vehicle is removed and sinters the silver and flux materials
Implementation Method 3
the conductive silver and frit mixture penetrate the insulating film
Data Source
AI summary
Described herein are a silicon semiconductor device and a conductive paste, including a flux material, for use in the front side of a solar cell device.