Conductive Paste for Solar Cell Electrodes
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Solution Overview
Problem
Existing solar cell electrodes face challenges in achieving low electrical resistance, which affects the overall efficiency of solar cells, particularly due to high series resistance in the electrode.
Innovation Solution
A conductive paste is developed comprising electrically conductive powder, glass frits with specific weight percentages of SiO2, Al2O3, and lead compounds, including lead fluoride, along with an organic medium, which is applied to a semiconductor substrate and fired to form a solar cell electrode, promoting sintering and binding while reducing series resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional glass compositions with high PbO content are used, then the electrode achieves good electrical properties, but the manufacturing complexity increases due to strict composition control requirements
Solution Approach 1:
The patent changes the chemical composition parameters of the glass frit by incorporating lead fluoride (PbF2) alongside PbO, and adjusting the SiO2 and Al2O3 content to specific ranges. This parameter modification allows achieving the desired electrical properties while simplifying the manufacturing process through more forgiving composition tolerances
Solution Approach 2:
The patent uses a composite glass frit system combining multiple oxides (PbO, PbF2, SiO2, Al2O3) in specific proportions. This composite approach creates a synergistic effect where the combination of materials achieves superior electrical properties while maintaining manufacturing simplicity through enhanced process window
2Strength
If glass frit with higher SiO2 content is used, then the binding strength improves, but the series resistance increases
Solution Approach 1:
The patent optimizes the SiO2 content to a specific range (8-26 wt%) rather than using high SiO2 content, and compensates by adjusting PbO (73-90 wt%) and Al2O3 (0.1-5 wt%) content. This balanced parameter adjustment maintains binding strength while preventing excessive series resistance through optimal electrical conductivity
3Reliability
If lead fluoride content in the lead compound is increased, then the electrical conductivity improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent sets the lead fluoride content within a specific range (5-28 wt% of total lead compound) rather than maximizing it. This optimized parameter range achieves sufficient electrical conductivity while maintaining a broader manufacturing window that tolerates normal production variations without requiring excessive precision
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 this conductive paste results in solar cell electrodes with improved electrical properties, specifically lower series resistance, enhancing the overall efficiency of the solar cells.
Implementation Method 1
Glass frits used in the pastes described herein promote sintering of the electrically conductive powder and also to facilitate binding of the electrode to the substrate
Data Source
AI summary
An objective of this present invention is to provide a conductive paste that could obtain good electrical property, for example series resistance in an electrode. An aspect of the present invention relates to a conductive paste which comprises electrically conductive powder; glass frit which comprises, based on weight percent (wt %) of the glass frit, 8-26 wt % of SiO2, 0.1-5 wt % of Al2O3, and 73-90 wt % of lead compound, wherein lead fluoride is contained in the range of 5-28 wt % based on the total weight of the lead compound; and organic medium.