Silver Powder Composition for Low-Resistance Short-Fire Electrodes
Solution Overview
Problem
Conventional silver powders used in electrically conductive pastes for forming solar cell electrodes result in high resistance values and require lengthy firing processes, which can damage substrates.
Innovation Solution
A silver powder with a crystalline size of 50 nm or less and a pressed density of 6.3 g/cm3, produced by mixing large-diameter and small-diameter silver powders with specific particle size distributions, is used to create a conductive film with low resistance, allowing for shorter firing times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional silver powder with larger crystalline size is used, then the paste can be fired at lower temperature, but the resistance value of the electrode becomes high
Solution Approach 1:
The patent changes the crystalline size parameter of silver powder to 50 nm or less, which fundamentally alters the sintering behavior during firing. This parameter change enables the formation of low-resistance electrodes at lower firing temperatures by promoting more effective particle bonding and electron transport pathways.
Solution Approach 2:
The patent creates a composite silver powder system by mixing large-diameter and small-diameter silver powders with specific size distributions. This composite structure optimizes both the green paste properties and the final sintered electrode characteristics, achieving low resistance at reduced firing temperatures.
2Reliability
If conventional silver powder is used, then the paste can be processed with standard firing conditions, but the firing period of time becomes long (2 to 15 minutes)
Solution Approach 1:
By changing the crystalline size parameter to 50 nm or less, the patent accelerates the sintering kinetics, enabling low-resistance electrode formation in significantly shorter firing times (reducing from 2-15 minutes to much shorter durations) while maintaining or improving electrode quality.
Solution Approach 2:
The silver powder is pre-prepared with optimized crystalline size and particle size distribution before paste formulation. This preliminary structuring of the powder enables rapid sintering during firing, reducing the required processing time while ensuring low electrode resistance.
3Reliability
If conventional silver powder is used, then the paste can be fired with standard parameters, but the substrate is severely damaged due to long firing time
Solution Approach 1:
The patent changes the crystalline size to 50 nm or less, which enables the decoupling of electrode quality formation from high-temperature prolonged exposure. This allows achieving low resistance electrodes through shorter, milder firing cycles that do not severely damage the substrate.
Solution Approach 2:
The optimized silver powder enables the firing process to quickly pass through the critical sintering stage, forming low-resistance electrodes in a short time window before substrate damage can occur. This 'rushing through' the sintering process protects the substrate from thermal damage.
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 silver powder effectively forms an electrically conductive film with low resistance even when fired for a shorter duration, improving solar cell efficiency and reducing substrate damage.
Implementation Method 1
when the paste of Patent Document 1 is fired to form an electrode of a solar cell
Implementation Method 2
the crystalline size of the large-diameter silver powder being measured by means of a powder X-ray diffractometer to be calculated
Implementation Method 3
the particle diameter (D50) of the large-diameter silver powder being a particle diameter corresponding to 50% of accumulation in a volume-based particle size distribution obtained by measuring the large-diameter silver powder in a wet process by means of a laser diffraction scattering particle size distribution analyzer
Data Source
AI summary
There are provided a silver powder, which is able to form an electrically conductive film having a low resistance value even if the period of time for firing an electrically conductive paste is shorter than that for firing conventional electrically conductive pastes when the silver powder is used as the material of the electrically conductive paste, and a method for producing the same. A large-diameter silver powder, which has a crystalline size of 50 nm or less and which has a particle diameter (D50) of 1 μm or more and 4 μm or less, the particle diameter (D50) of the large-diameter silver powder being a particle diameter corresponding to 50% of accumulation in a particle size distribution of the large-diameter silver powder, is mixed with a small-diameter silver powder, which has a crystalline size of 50 nm or less and which has a particle diameter (D50) of 0.3 μm or more and less than 1 μm, the particle diameter (D50) of the small-diameter silver powder being a particle diameter corresponding to 50% of accumulation in a particle size distribution of the small-diameter silver powder, to produce a silver powder, which has a crystalline size of 50 nm or less and which has a pressed density of 6.3 g/cm3 or more.