Conductive Paste for Solar Cells with Oxide Penetration
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Solution Overview
Problem
Conventional conductive paste compositions for photovoltaic devices face challenges in achieving reliable adhesion and electrical properties, particularly when forming electrodes on lightly doped silicon wafers, as they often fail to penetrate anti-reflective layers effectively without damaging the underlying semiconductor.
Innovation Solution
A paste composition comprising 93-99% electrically conductive metal and 1-7% oxide-based fusible material, specifically formulated with lead-tellurium-oxide (Pb—Te—O) glass, which penetrates insulating layers and forms robust, low-resistance connections to the semiconductor substrate upon firing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive paste compositions are used to form electrodes on lightly doped silicon wafers, then the paste can be applied to the surface, but it fails to penetrate the anti-reflective layer effectively without damaging the underlying semiconductor
Solution Approach 1:
The paste composition modifies its chemical and physical parameters during firing to enable controlled penetration. The oxide-based fusible material undergoes phase changes and chemical reactions at specific temperatures to etch through the anti-reflective layer selectively, while the conductive metal particles maintain structural integrity to avoid substrate damage.
Solution Approach 2:
The invention uses a composite paste composition combining conductive metal particles (93-99% by weight) with oxide-based fusible material (1-7% by weight). This composite structure allows the paste to simultaneously provide mechanical strength, electrical conductivity, and chemical etching capability to penetrate the insulating layer without damaging the substrate.
2Reliability
If the paste composition penetrates the anti-reflective layer effectively, then good electrical contact is achieved, but adhesion reliability may be compromised
Solution Approach 1:
The paste composition exhibits different functional properties in different regions and stages of the firing process. The oxide-based fusible material provides localized chemical activity at the paste-insulating layer interface to enable penetration and electrical contact, while the conductive metal particles maintain structural integrity and adhesion to the substrate throughout the process.
3Reliability
If conventional paste compositions are used, then manufacturing process is simple, but electrical performance and conversion efficiency are insufficient
Solution Approach 1:
The invention optimizes specific parameters of the paste composition, particularly the weight percentage ranges of conductive metal (93-99%) and oxide-based fusible material (1-7%), to achieve superior electrical performance. These parameter optimizations enable low series resistance and high conversion efficiency while maintaining compatibility with existing screen printing and firing processes.
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 enables the formation of high-quality electrodes with improved electrical performance, including high photovoltaic conversion efficiency, low series resistance, and strong mechanical adhesion, effectively addressing the limitations of previous paste compositions on lightly doped emitter wafers.
Implementation Method 1
an oxide-based fusible material... which penetrates insulating layers and forms robust, low-resistance connections to the semiconductor substrate upon firing
Implementation Method 2
forms high-quality electrodes with improved electrical performance... strong mechanical adhesion
Data Source
AI summary
The present invention provides a thick-film paste composition comprising an electrically conductive metal and an oxide composition dispersed in an organic medium. The paste composition is printed on the front side of a solar cell device having one or more insulating layers and fired to form an electrode, and is suitable for devices having both highly and lightly doped emitter structures.