Lead-Tungsten Thick-Film Paste for Solar Cell Contact Penetration
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Solution Overview
Problem
Conventional solar cell technologies face challenges in forming effective electrical contacts with semiconductor substrates due to anti-reflective coatings, requiring conductive inks that can penetrate these coatings and provide strong bonds at low temperatures to enhance efficiency.
Innovation Solution
A thick-film paste composition comprising 80-99.5 wt% of an electrically conductive metal, 0.5 to 20 wt% of a vanadium-free, tellurium-free lead-tungsten-based oxide, and an organic medium, which is applied and fired to form electrodes that penetrate insulating layers and establish electrical contact with the semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional conductive inks are used, then the anti-reflective coating provides good light absorption, but the insulating layer impairs electron flow and prevents effective electrical contact
Solution Approach 1:
The conductive ink formulation is prepared in advance with specific glass frit compositions and metal particle sizes that enable penetration of the anti-reflective coating during firing. The paste is designed with pre-determined rheological properties and chemical reactivity to overcome the insulating barrier and establish electrical contact with the semiconductor substrate.
Solution Approach 2:
The invention modifies the chemical composition parameters of the conductive ink by incorporating specific glass frits with controlled softening points, metal particle size distributions, and organic vehicle formulations. These parameter changes enable the paste to penetrate the anti-reflective coating at optimized firing temperatures while maintaining electrical conductivity and mechanical adhesion.
2Reliability
If high firing temperatures are used to penetrate the anti-reflective coating, then electrical contact is improved, but manufacturing cost and energy consumption increase
Solution Approach 1:
The invention changes the chemical composition parameters of the glass frit to include lower melting point components and optimized softening characteristics. This enables the paste to become sufficiently fluid at reduced firing temperatures to penetrate the anti-reflective coating and form electrical contact, thereby reducing the thermal energy required for the firing process.
Solution Approach 2:
The conductive ink is formulated as a composite material system combining glass frit, metal particles, and organic vehicle in specific proportions. The glass frit acts as a flux that lowers the effective firing temperature needed for penetration, while the metal particles provide conductivity. This composite approach enables effective electrical contact formation at lower temperatures than would be required for simple metal deposits.
3Reliability
If the conductive ink penetrates the anti-reflective coating effectively, then electrical contact is improved, but the bond strength between the metal contact and substrate may be compromised
Solution Approach 1:
The glass frit component performs multiple functions simultaneously: it acts as a flux to facilitate penetration of the anti-reflective coating, serves as a bonding agent to adhere the metal particles to the semiconductor substrate, and provides mechanical strength to the fired paste structure. This multi-functionality ensures that effective electrical contact and strong bonding are achieved together rather than traded off against each other.
Solution Approach 2:
The invention uses a composite paste formulation where glass frit, metal particles, and organic binders work synergistically. The glass frit matrix embeds the metal particles and bonds to the substrate, creating a mechanically strong interface while maintaining electrical conductivity pathways. The composite structure ensures that penetration and bonding are achieved simultaneously.
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 solution enables the formation of strong, efficient electrical contacts that improve solar cell performance by allowing the thick-film paste to penetrate anti-reflective coatings and form bonds with the substrate at low temperatures, enhancing energy conversion efficiency.
Implementation Method 1
firing the semiconductor substrate, the one or more insulating films, and the thick-film paste wherein the organic medium of the thick film paste is volatilized
Implementation Method 2
the conductive ink should penetrate the anti-reflective coating during firing to form metal contacts having electrical contact with the semiconductor substrate
Data Source
Figure 1A~1F
AI summary
The present invention provides a thick-film paste for printing the front side of a solar cell device having one or more insulating layers and a method for doing so. The thick-film paste comprises a source of an electrically conductive metal and a lead-tungsten-based oxide dispersed in an organic medium. The invention also provides a semiconductor device comprising an electrode formed from the thick-film paste.