Conductive Paste for Solar Cells with Tellurium Glass Frit
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Solution Overview
Problem
The contact resistance between solar cell electrodes and the semiconductor substrate is difficult to maintain stably due to the composition of tellurium-based glass frit, affecting the cell's conversion efficiency and characteristics.
Innovation Solution
A conductive paste with a glass frit composition of 35 to 90 mol% TeO2, 5 to 50 mol% ZnO, 1 to 20 mol% Bi2O3, and 0.1 to 15 mol% of Li, Na, or K oxides, along with optional additives like Mg, Ca, Sr, Ba, Mn, Cu, Ag, V, B, P, Ti, Co, Nb, Fe, Ni, Al, Zr, Ta, Si, Sn, and Sb, to optimize fire-through performance and reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tellurium-based glass frit is used to control fire-through performance, then the light-receiving surface electrodes do not deeply erode the semiconductor substrate, but the contact resistance becomes difficult to maintain stably
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition ratios of multiple oxides in the glass frit. Specifically, it sets TeO2 at 35-90 mol%, ZnO at 5-50 mol%, Bi2O3 at 1-20 mol%, and adds 0.1-15 mol% of Li, Na, or K oxides. This multi-parameter optimization stabilizes the contact resistance while maintaining fire-through control, resolving the contradiction between reliability and compositional stability.
Solution Approach 2:
The patent creates a composite glass frit material combining multiple oxide components (TeO2, ZnO, Bi2O3, and alkaline metal oxides) to achieve synergistic effects. This composite formulation provides both controlled fire-through performance and stable contact resistance, eliminating the instability issue of pure tellurium-based frits while maintaining substrate protection.
2Strength
If a low-softening point glass frit is used to enhance adhesive strength, then the adhesive strength between light-receiving surface electrodes and semiconductor substrate is improved, but the fire-through may advance excessively causing electrode penetration and substrate erosion
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass frit to achieve an optimal balance. By setting TeO2 at 35-90 mol% and ZnO at 5-50 mol%, the formulation achieves appropriate softening point and adhesive strength without excessive fire-through, preventing substrate erosion while maintaining strong bonding between electrodes and substrate.
Solution Approach 2:
The patent applies local quality by creating a glass frit composition that provides different functional properties at different stages of the firing process. The formulation ensures strong adhesion during bonding while controlling the extent of fire-through to prevent harmful substrate erosion, achieving localized optimization of both adhesive strength and substrate protection.
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 optimized glass frit composition in the conductive paste lowers contact resistance, enhancing the energy conversion efficiency and cell characteristics of solar cells while being lead-free.
Implementation Method 1
the glass frit is fused in a firing process
Implementation Method 2
the conductive film is sintered to form light-receiving surface electrodes
Implementation Method 3
the antireflective film located at a lower layer of the conductive film is decomposed and removed
Data Source
Figure 1~2
Figure 3
AI summary
The conductive paste contains a conductive powder, a glass frit, and an organic vehicle. The glass frit contains 35-90 mol% of Te in terms of TeO2, 5-50 mol% of Zn in terms of ZnO, and 1-20 mol% of Bi in terms of Bi2O3, and contains 0.1-15 mol% of at least one element selected from the group of Li, Na, and K in terms of oxides thereof. The conductive paste is used to form light-receiving surface electrodes (3). A conductive paste appropriate for formation of electrodes of a solar cell capable of reducing contact resistance between the electrode (3) and a semiconductor substrate (1) is thereby achieved, the use of the conductive paste obtaining high energy conversion efficiency and attaining a solar cell having excellent cell characteristics.