Conductive Aluminum Paste for Solar Cell Electrodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional silicon solar cells face challenges in achieving high electro-optical conversion efficiency and stability due to high sheet resistance and adhesion issues in their electrodes, particularly the back side electrode, which affects the fill factor and overall performance.
Innovation Solution
A conductive aluminum paste is developed, comprising organic carrier, aluminum powder, glass frit, and nano-scale metal particles (such as gold, silver, copper, or lead), which reduces sheet resistance and enhances adhesion, thereby improving the electro-optical conversion efficiency and stability of silicon solar cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional aluminum paste is used for back side electrode, then manufacturing cost is reduced, but sheet resistance is high and adhesion is poor
Solution Approach 1:
The patent uses composite aluminum paste containing aluminum powder, silver powder, copper powder, glass frit, and organic carrier. The combination of different metals (Al, Ag, Cu) creates a composite material that achieves both low sheet resistance and high adhesion while maintaining cost-effectiveness compared to pure silver paste
Solution Approach 2:
The patent optimizes particle size distribution with D10=0.5-2μm, D50=3-6μm, D90=8-15μm for aluminum powder and D50=0.5-3μm for nano-scale metal particles. This parameter optimization of particle size distribution improves adhesion and reduces sheet resistance without significantly increasing cost
2Reliability
If silver paste is used for light incident side electrode, then conductivity is improved, but surface area for light incident is reduced
Solution Approach 1:
The patent uses screen printing technology with optimized paste viscosity and particle size distribution to achieve fine line patterns with high conductivity. The optimized paste formulation allows printing of thinner, more precise electrode lines that maintain low resistance while occupying less surface area
Solution Approach 2:
The patent applies different electrode patterns locally: bus electrodes for high current collection and finger electrodes for distributed collection. The conductive aluminum paste enables localized optimization of electrode geometry to minimize light blocking while maintaining conductivity requirements
3Reliability
If sintering temperature is increased to improve electrode formation, then aluminum diffusion into P-type semiconductor is enhanced, but risk of substrate damage and warpage increases
Solution Approach 1:
The patent optimizes sintering temperature to 700-900°C and holds it for 30-120 seconds. This parameter optimization achieves sufficient aluminum diffusion for good electrode formation and P+ layer creation while avoiding substrate damage and warpage that occur at higher temperatures
Solution Approach 2:
The glass frit component in the conductive aluminum paste acts as a flux that facilitates aluminum diffusion at lower temperatures. The glass matrix provides a controlled release mechanism for aluminum atoms, enabling effective doping at 700-900°C without requiring higher temperatures that would damage the substrate
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 use of nano-scale metal particles in the conductive aluminum paste results in lower sheet resistance, increased adhesion, and improved electro-optical conversion efficiency, enhancing the performance and stability of silicon solar cells, particularly in the back side electrode, leading to higher output and better package stability.
Implementation Method 1
addition of the nano-scale metal particle is used to reduce a sheet resistance value of the conductive aluminum paste
Implementation Method 2
the aluminum atoms in the aluminum paste are diffusing into the P-type semiconductor (P-type diffused layer) to form the P+ layer
Implementation Method 3
the sintering process, the high temperature (usually in the range from 600 degrees centigrade to 1000 degrees centigrade) is used to sinter the semiconductor substrate
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
This present disclosure relates to conductive aluminum paste for fabricating a silicon solar cell. Herein, the conductive aluminum paste is composed of organic carrier, aluminum powder, nano-scale metal particle, and glass frit, wherein the nano-scale metal particle has a particle size distribution D50 in the range from 10 nanometers to 1000 nanometers and the weight percentage of the nano-scale metal particle associated with the conductive aluminum paste is around 0.1 through 10 wt%. Furthermore, the characteristics of the conductive aluminum paste are for reducing the sheet resistance value of the electrode, increasing the adhesion in the silicon solar cell package module, and enhancing the electro-optical conversion efficiency of the silicon solar cell.