Silver Alloy Electrode Paste for Solar Cells
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Solution Overview
Problem
Existing solar cell electrode compositions face challenges in minimizing serial resistance and maintaining p-n junction stability due to increased contact resistance and varying baking temperatures, especially as solar cell areas expand and wafers with different resistances are used.
Innovation Solution
A composition comprising silver powder, a silver alloy with a eutectic point between 150° C. to 900° C., glass frit, and an organic vehicle, which includes specific metal oxides and additives to enhance adhesion, reduce contact resistance, and provide thermal stability, allowing for lower sintering temperatures and improved electromechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional silver paste compositions are used, then manufacturing process is simple, but serial resistance increases and contact resistance increases
Solution Approach 1:
The patent uses composite materials by combining silver powder with specific metal alloys (containing In, Sr, Ce, Zn, Te, Sn, Se, Eu, La, Sb, Pb, Na, Li, Pr, As, or Bi) and glass frit in defined weight ratios. This composite composition reduces serial resistance and contact resistance while maintaining manufacturability, directly resolving the contradiction between reliability improvement and composition complexity.
Solution Approach 2:
The patent changes the chemical composition parameters of the silver paste by incorporating specific metal alloys with controlled weight ratios (0.1-40 wt%) and glass frit content (0.5-20 wt%). These parameter changes optimize electrical conductivity and reduce contact resistance, addressing the serial resistance issue while managing composition complexity through defined ranges.
2Strength
If baking temperature is increased to improve adhesion, then adhesion improves, but p-n junction stability deteriorates
Solution Approach 1:
The patent changes the chemical composition of the paste by adding glass frit (0.5-20 wt%) and metal alloys that promote adhesion at lower temperatures. This allows achieving sufficient adhesion strength without increasing baking temperature, thereby protecting p-n junction stability while maintaining bond strength.
Solution Approach 2:
The glass frit acts as an intermediary material that enhances adhesion between the silver paste and the substrate at lower temperatures. The glass frit components (including ZnO-SiO2, ZnO-B2O3-SiO2, Bi2O3, PbO, and other glass systems) provide a bonding mechanism that reduces the required baking temperature, thus protecting the p-n junction while achieving adequate adhesion.
3Power
If solar cell area is expanded to increase power output, then power output increases, but contact resistance increases
Solution Approach 1:
The patent employs composite materials with specific metal alloys and glass frit that enhance electrical conductivity and reduce contact resistance. This allows expanding solar cell area to increase power output while maintaining low contact resistance across the larger surface area through the improved paste composition.
Solution Approach 2:
By changing the compositional parameters of the silver paste (adding metal alloys at 0.1-40 wt% and glass frit at 0.5-20 wt%), the patent optimizes electrical conductivity to compensate for the increased contact resistance that would normally accompany larger cell areas, enabling power output expansion without sacrificing reliability.
4Reliability
If sintering temperature is reduced to protect p-n junction, then p-n junction stability improves, but adhesion deteriorates
Solution Approach 1:
The glass frit serves as an intermediary that enables adhesion at lower sintering temperatures. The patent specifies glass frit containing various oxide systems (ZnO-SiO2, ZnO-B2O3-SiO2, Bi2O3, PbO, etc.) that become active at reduced temperatures, providing bonding capability while protecting the p-n junction from thermal damage.
Solution Approach 2:
The composite paste composition including metal alloys (0.1-40 wt%) and glass frit (0.5-20 wt%) creates a material system that achieves adequate adhesion strength at lower sintering temperatures, resolving the contradiction between protecting p-n junction stability and maintaining adhesion quality.
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 achieves low serial resistance, enhanced conversion efficiency, and improved fill factor by minimizing contact resistance and securing thermal stability across a wide sintering temperature range, thereby stabilizing the p-n junction.
Implementation Method 1
a silver alloy (AgX) that includes silver (Ag) and a metal (X), the silver alloy having a eutectic point of about 150° C. to about 900° C.
Implementation Method 2
Solar cells generate electricity using the photovoltaic effect of a p-n junction which converts photons of sunlight into electricity
Data Source
AI summary
A composition for solar cell electrodes includes silver powder; a silver alloy (AgX) that includes silver (Ag) and a metal (X), the silver alloy having a eutectic point of about 150° C. to about 900° C.; a glass frit; and an organic vehicle.