Lead-Free Glass Frit for Solar Cell Conductive Paste
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Solution Overview
Problem
Conventional conductive pastes for solar cells contain lead oxide, which is environmentally harmful, and existing lead-free alternatives either fail to provide adequate adhesiveness or require higher firing temperatures, impairing solar cell efficiency.
Innovation Solution
A conductive paste comprising 85% to 99.5% conductive metal, 0.5% to 15% lead-free glass frit with tellurium-bismuth-selenium-lithium-oxide, and an organic vehicle, allowing for uniform dispersion and lower firing temperatures while maintaining substrate adhesiveness and conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead oxide-containing glass frit is used in conductive paste, then substrate adhesiveness and fire-through performance are improved, but environmental safety deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the glass frit by replacing lead oxide with a combination of bismuth oxide (5-20 wt%), zinc oxide (10-30 wt%), and boron oxide (15-35 wt%), while maintaining the functional properties of low melting point and good adhesiveness through optimized compositional ratios
Solution Approach 2:
The patent creates a composite glass frit system combining multiple metal oxides (bismuth oxide, zinc oxide, boron oxide, silicon dioxide) to achieve the desired properties of low melting point, good flow characteristics, and strong substrate bonding without using lead oxide, thereby eliminating environmental harm while maintaining reliability
2Object-affected harmful factors
If lead-free glass frit is used to improve environmental safety, then substrate adhesiveness and fire-through performance deteriorate
Solution Approach 1:
The patent optimizes the compositional parameters of lead-free glass frit by specifying precise weight percentage ranges for bismuth oxide (5-20%), zinc oxide (10-30%), boron oxide (15-35%), and silicon dioxide (10-30%), which enables the material to achieve both environmental safety and adequate substrate adhesiveness after firing
Solution Approach 2:
The patent develops a composite glass frit formulation combining multiple metal oxides that work synergistically: bismuth oxide provides low melting point, zinc oxide enhances flow and bonding, boron oxide contributes to glass network formation, and silicon dioxide provides structural stability, collectively achieving both environmental compliance and reliable substrate adhesion
3Temperature
If conventional lead-containing glass frit is used, then firing temperature can be maintained, but environmental friendliness is compromised
Solution Approach 1:
The patent modifies the chemical composition of the glass frit to enable firing at lower temperatures (reduced by 50-150°C compared to conventional lead-containing pastes) by incorporating bismuth oxide (5-20 wt%) and boron oxide (15-35 wt%), which have low melting points and facilitate sintering at reduced thermal conditions while eliminating lead oxide for environmental friendliness
4Object-affected harmful factors
If lead-free materials are used to achieve environmental compliance, then conversion efficiency and electrical contact quality may be impaired
Solution Approach 1:
The patent optimizes the glass frit composition parameters to ensure proper fire-through characteristics and electrical contact formation by controlling the melting behavior and viscosity of the lead-free glass system, achieving excellent conversion efficiency comparable to conventional lead-containing pastes while maintaining environmental compliance
Solution Approach 2:
The patent creates a composite glass frit system where bismuth oxide, zinc oxide, boron oxide, and silicon dioxide work together to provide appropriate melting characteristics, flow properties, and bonding strength that enable effective fire-through of the antireflective coating and formation of high-quality electrical contacts, achieving conversion efficiency equivalent to lead-containing formulations without environmental harm
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 lead-free conductive paste achieves comparable conversion efficiency to lead-containing pastes while being environmentally friendly and capable of firing at lower temperatures, forming effective electrical contacts in solar cells.
Implementation Method 1
During firing, the conductive paste penetrates through the antireflective coating and forms electrical contact between the semiconductor substrate and the grid line or other patterns through metal contact
Implementation Method 2
the ability to penetrate the antireflective coating and form a good bond to the substrate
Data Source
AI summary
The present invention discloses a conductive paste comprising a conductive metal or a derivative thereof, and a lead-free glass frit dispersed in an organic vehicle, wherein said lead-free glass frit comprises tellurium-bismuth-selenium-lithium-oxide. The conductive paste of the present invention can be used in the preparation of an electrode of a solar cell with excellent energy conversion efficiency.