Lead-Free Conductive Paste for Solar Cell Electrodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional conductive pastes for solar cells contain lead oxide, which is environmentally harmful, and require high firing temperatures to penetrate antireflective coatings effectively, impairing electrical contact and solar cell efficiency.
Innovation Solution
A conductive paste comprising 85-99.5% conductive metal, 0.5-15% lead-free glass frit with tellurium-bismuth-zinc-tungsten-oxide, and an organic vehicle, allowing for lower temperature firing and improved substrate adhesiveness, using selenium and additional metal oxides for enhanced properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead oxide-containing glass frit is used in conductive paste, then fire-through capability and substrate adhesiveness are improved, but environmental harm increases and firing temperature must be maintained at high levels
Solution Approach 1:
The patent changes the chemical composition parameters of the glass frit by replacing lead oxide with alternative oxides (bismuth oxide 20-40 wt%, zinc oxide 10-30 wt%, boron oxide 10-30 wt%, silicon dioxide 10-30 wt%). This parameter substitution maintains the glass frit's ability to dissolve antireflective coating and form strong bonds while eliminating environmental harm from lead content.
Solution Approach 2:
The patent creates a composite glass frit system combining multiple metal oxides (bismuth oxide, zinc oxide, boron oxide, silicon dioxide, and optional additives like selenium oxide or aluminum oxide). This composite formulation achieves the desired fire-through capability and adhesion properties without relying on harmful lead oxide, thus resolving the contradiction between performance and environmental safety.
2Reliability
If lead oxide-containing glass frit is used in conductive paste, then substrate adhesiveness and fire-through are improved, but firing temperature remains high
Solution Approach 1:
The patent modifies the glass transition and softening temperature parameters of the glass frit through compositional adjustments. The specific ratio of low-melting-point oxides (boron oxide 10-30 wt%, zinc oxide 10-30 wt%) is optimized to reduce the firing temperature from conventional high levels to 700-900°C, while maintaining adequate substrate adhesiveness through the composite oxide system.
3Reliability
If conventional lead-containing conductive paste is used, then conversion efficiency is achieved, but environmental friendliness is compromised
Solution Approach 1:
The patent changes the chemical composition parameters of the glass frit component in the conductive paste by substituting lead oxide with environmentally friendly alternative oxides. This parameter substitution eliminates harmful lead content while maintaining the electrical contact quality and conversion efficiency through optimized ratios of bismuth oxide, zinc oxide, boron oxide, and silicon dioxide.
Solution Approach 2:
The patent develops a composite, lead-free glass frit formulation that combines multiple metal oxides to achieve the necessary performance characteristics for maintaining conversion efficiency. The synergistic interaction between bismuth oxide, zinc oxide, boron oxide, and silicon dioxide creates a material that matches or exceeds the performance of lead-containing formulations while being environmentally friendly.
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, forming effective electrical contacts at lower temperatures, promoting environmentally friendly and efficient solar cell production.
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
after firing, 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-zinc-tungsten-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.