Conductive Paste Composition for Solar Cell Electrodes
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Solution Overview
Problem
Conventional conductive paste compositions for photovoltaic cells face challenges in achieving simultaneous good electrical and mechanical properties, particularly in penetrating anti-reflective layers without damaging the underlying semiconductor, and in forming strong adhesion between electrodes and substrates during firing.
Innovation Solution
A paste composition comprising 85 to 99.75% electrically conductive metal and 0.25 to 15% of an oxide-based component with a lead-tellurium-based oxide and a bismuth-silicon-oxide, which includes specific weight percentages of Bi2O3, SiO2, ZnO, TeO2, and other oxides, dispersed in an organic vehicle, is used to form electrodes that penetrate insulating layers and provide strong adhesion during firing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive paste compositions are used to penetrate anti-reflective layers, then electrical conductivity is improved, but mechanical adhesion deteriorates
Solution Approach 1:
The patent uses a composite paste composition containing silver particles (for conductivity), glass frit (for adhesion and penetration), and organic vehicle. This composite structure allows simultaneous achievement of electrical conductivity through silver network formation and mechanical adhesion through glass frit bonding to the substrate, resolving the contradiction between electrical performance and mechanical strength.
Solution Approach 2:
The patent modifies the chemical composition parameters of the paste, specifically the ratio of silver particles to glass frit, particle size distribution, and organic vehicle composition. By optimizing these parameters, the paste achieves appropriate viscosity for screen printing, sufficient penetration capability through anti-reflective layers, and strong adhesion to the underlying substrate, thereby resolving the contradiction between electrical conductivity and mechanical adhesion.
2Reliability
If paste composition penetrates anti-reflective layers effectively, then electrical contact is improved, but damage to underlying semiconductor occurs
Solution Approach 1:
The patent carefully controls the firing temperature parameters and paste composition to enable selective penetration. The glass frit composition and organic vehicle are designed to react with and penetrate the anti-reflective layer at specific temperature ranges, while the underlying semiconductor remains unaffected. This parameter optimization allows effective electrical contact formation without causing semiconductor damage.
Solution Approach 2:
The glass frit acts as an intermediary substance that facilitates controlled penetration through the anti-reflective layer. It chemically reacts with the anti-reflective layer to create conductive pathways while protecting the underlying semiconductor from direct exposure to aggressive paste components and excessive temperatures, thus resolving the contradiction between penetration effectiveness and semiconductor protection.
3Strength
If strong adhesion is formed during firing, then mechanical strength is improved, but electrical conductivity deteriorates
Solution Approach 1:
The patent employs a composite paste where silver particles provide the electrical conductive network while glass frit provides the adhesive bonding matrix. The silver particles remain as discrete conductive elements within the glass frit matrix, ensuring that strong adhesion through glass frit bonding does not compromise the electrical conductivity provided by the silver particle network. This composite structure resolves the contradiction between adhesion strength and electrical conductivity.
Solution Approach 2:
The paste composition is designed with different components having localized functions: silver particles concentrate in regions requiring electrical conductivity, while glass frit concentrates in regions requiring mechanical adhesion. During firing, silver particles sinter to form conductive pathways while glass frit forms the adhesive bond to the substrate. This spatial differentiation of material properties resolves the contradiction between local adhesion requirements and local conductivity requirements.
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 composition enables the formation of electrodes with high photovoltaic conversion efficiency, low series resistance, and good mechanical adhesion, improving the overall electrical performance and manufacturing efficiency of photovoltaic cells.
Implementation Method 1
an oxide-based component comprising a first fusible material and a separate second fusible material
Implementation Method 2
which comprises, by weight percent: 30 to 80% Bi2O3, 1 to 50% SiO2, 0 to 40% ZnO, 0 to 22% TeO2
Implementation Method 3
an organic vehicle in which the constituents of the inorganic solids portion are dispersed
Implementation Method 4
conductive metal particles are sintered to form a sintered metal layer
Implementation Method 5
forming strong adhesion between electrodes and substrates during firing
Implementation Method 6
improving the overall electrical performance and manufacturing efficiency of photovoltaic cells
Data Source
AI summary
The present invention provides a thick-film paste composition for printing the front side of a solar cell device having one or more insulating layers. The thick-film paste comprises an electrically conductive metal and a dual-frit oxide composition dispersed in an organic medium.