Sinterable Metal Particles for Low Resistivity Solar Paste
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Solution Overview
Problem
Current conductive pastes for solar photovoltaic cells, particularly those used in silicon heterojunction solar cells, face limitations in achieving low resistivity and fine line print performance, leading to increased shadow losses and emitter resistance, which hinder efficiency gains.
Innovation Solution
A conductive paste composition comprising metal particles with specific characteristics, such as a ψ value <0.0020, high crystallinity, and anisotropy, dispersed in a solvent and resin carrier, optimized for use as finger and busbar materials in solar photovoltaic cells, enabling improved electrical conductivity and fine line printing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional conductive pastes are used, then the paste can be printed and cured, but the resistivity remains high and fine line print performance is poor
Solution Approach 1:
The patent changes the crystalline structure parameters of metal particles by controlling the ψ value (peak position parameter in XRD) to be less than 0.0020 and maintaining high crystallinity (greater than 70%). This parameter change in the metal particle structure enables both fine line printability and low resistivity, resolving the contradiction between manufacturing precision and electrical conductivity.
Solution Approach 2:
The patent uses composite metal particles that combine high crystallinity with specific crystallographic orientation (low ψ value). This composite structure of highly ordered crystalline regions provides both the structural integrity needed for fine line printing and the electrical pathways needed for low resistivity.
2Loss of energy
If metal line width is reduced to reduce shadow losses, then transparency increases, but manufacturing precision and adhesion become more difficult to maintain
Solution Approach 1:
By changing the crystalline structure parameters (ψ value < 0.0020 and crystallinity > 70%), the patent enables metal particles to form adherent, precise lines at narrower widths. The highly ordered crystal structure provides better particle packing and sintering behavior, allowing narrow lines to maintain structural integrity and adhesion while reducing shadow losses.
3Temperature
If low temperature curing is used, then the process is simpler and suitable for heterojunction cells, but electrical conductivity and line resistance are insufficient
Solution Approach 1:
The patent changes the metal particle crystalline structure to have very low ψ values and high crystallinity, which enables effective sintering and conductivity formation at lower temperatures. The pre-organized crystalline structure reduces the energy barrier for sintering, allowing low temperature curing to achieve the same electrical conductivity that would otherwise require high temperatures.
4Reliability
If high crystallinity metal particles are used, then electrical conductivity improves, but the complexity of particle characterization and selection increases
Solution Approach 1:
The patent replaces complex multi-parameter particle characterization with a single, easily measurable parameter (ψ value from XRD). Instead of characterizing multiple aspects of particle morphology and structure, the ψ value serves as a comprehensive indicator that correlates with both crystallinity and electrical performance, simplifying the selection process.
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 proposed solution achieves lower resistivity and enhanced fine line print performance, reducing shadow losses and increasing the efficiency of solar photovoltaic cells by utilizing metal particles with defined ψ values, crystallinity, and anisotropy, thereby improving electrical conductivity and adhesion.
Implementation Method 1
sinterable metal particles having a ψ value, as defined by X-ray diffraction
Implementation Method 2
high crystallinity
Data Source
AI summary
The present invention relates to a conductive paste composition for solar photovoltaic cells comprising metal particles dispersed in a suitable carrier therefor, wherein said carrier comprises a solvent and a resin, and wherein at least a portion of said metal particles are characterized by having a ψ value, as defined by X-ray diffraction<0.0020, having at least 50% degree of crystallinity, and being anisotropic with respect to crystallographic direction.