Dual Metal Paste Grid Electrode for Silicon Solar Cells
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Solution Overview
Problem
Conventional silicon solar cell production methods for forming grid electrodes on the front-side of solar cells face inefficiencies in electrical efficiency and adhesion between printed layers, particularly when using the same metal paste for multiple printings.
Innovation Solution
A process involving the sequential printing and firing of two metal pastes, A and B, with distinct glass frit content and fire-through capabilities, where metal paste A has a higher glass frit content for initial contact and metal paste B has a lower glass frit content for subsequent layer formation, enhancing electrical contact and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the same metal paste is used for multiple printings to form grid electrodes, then the manufacturing process is simple, but the electrical efficiency and adhesion between printed layers deteriorate
Solution Approach 1:
The invention segments the metal paste application process into two distinct printing steps: first printing a metal paste with high glass frit content (5-15 wt%) to create a glass-rich layer that fires through the ARC, then printing a metal paste with low glass frit content (0-3 wt%) to form the conductive grid pattern. This segmentation allows each layer to perform its specific function optimally, resolving the contradiction between manufacturing simplicity and electrical performance.
Solution Approach 2:
The invention applies local quality by using different metal paste compositions in different spatial locations and sequential layers. The first printed paste (high glass frit) is applied in specific patterns to create fire-through pathways, while the second printed paste (low glass frit) is applied in grid patterns for electrical conduction. This localized differentiation of material properties optimizes both adhesion and electrical efficiency.
2Strength
If metal paste with high glass frit content is used, then adhesion and fire-through capability are improved, but electrical conductivity deteriorates
Solution Approach 1:
The invention divides the metal paste composition into two segments: a high glass frit paste (5-15 wt%) for creating strong adhesion and fire-through pathways, and a low glass frit paste (0-3 wt%) for providing excellent electrical conductivity. By applying these segmented compositions in sequence rather than mixing them, the patent achieves both strong adhesion and high conductivity simultaneously.
Solution Approach 2:
The invention creates a composite structure through sequential printing of two metal pastes with different glass frit contents. The resulting grid electrode is a composite of high glass frit material (for adhesion and fire-through) and low glass frit material (for conductivity), combining the advantages of both material compositions in a single functional electrode structure.
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
This process improves the electrical efficiency and solder adhesion of silicon solar cells by optimizing the glass frit content in each metal paste, leading to better contact formation and overall performance.
Implementation Method 1
printing and drying a metal paste A having fire-through capability on the ARC layer
Implementation Method 2
the metal paste A comprises an organic vehicle and an inorganic content comprising (a1)) at least one electrically conductive metal powder and (a2) 0.5 to 8 wt.-% of glass frit
Implementation Method 3
printing and drying a metal paste A having fire-through capability on the ARC layer
Data Source
AI summary
A process of forming a front-grid electrode on a silicon wafer having an ARC layer, comprising the steps:(1) printing and drying a metal paste A comprising an inorganic content comprising 0.5 to 8 wt.-% of glass frit and having fire-through capability, wherein the metal paste A is printed on the ARC layer to form a bottom set of thin parallel finger lines,(2) printing and drying a metal paste B comprising an inorganic content comprising 0.2 to 3 wt.-% of glass frit over the bottom set of finger lines, wherein the metal paste B is printed in a grid pattern which comprises (i) thin parallel finger lines forming a top set of finger lines superimposing the bottom set of finger lines and (ii) busbars intersecting the finger lines at right angle, and(3) firing the double-printed silicon wafer,wherein the inorganic content of metal paste B contains less glass frit plus optionally present other inorganic additives than the inorganic content of metal paste A.