Conductive Paste with Synthetic Clay for Low-Resistance Solar Contacts
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Solution Overview
Problem
Conventional photovoltaic cell manufacturing processes face challenges in achieving high efficiency and robust electrical contacts due to the need for efficient penetration of insulating layers and formation of strong bonds between conductive pastes and semiconductor substrates, particularly on the front side of solar cells.
Innovation Solution
A conductive paste composition comprising 70-96% electrically conductive metal, 0.1-15% fusible material, 0.1-2% synthetic clay additive, and 0-15% etchant additives, along with an organic medium, is used to form electrodes that can penetrate insulating layers and provide robust electrical contacts during firing, enhancing the electrical performance of photovoltaic cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive paste is used to form front-side electrodes, then the insulating layer must be removed to allow contact with the semiconductor surface, but this removal process increases manufacturing complexity and reduces device reliability
Solution Approach 1:
The patent introduces an intermediary substance (fluorinated compound or etchant) within the conductive paste that chemically reacts with the insulating layer during firing. This intermediary enables the paste to penetrate and bond through the insulating layer without requiring its removal, thus resolving the contradiction between maintaining the insulating layer and achieving reliable electrical contact
Solution Approach 2:
The patent modifies the chemical composition parameters of the conductive paste by incorporating fluorinated compounds or etchants. These parameter changes enable the paste to chemically interact with and penetrate the insulating layer at firing temperatures, eliminating the need for mechanical removal and simplifying the manufacturing process while ensuring reliable contact
2Reliability
If the insulating layer is removed to allow electrode contact, then electrical connection is achieved, but the mechanical strength and stability of the electrode-substrate bond are reduced
Solution Approach 1:
The fluorinated compound or etchant acts as a chemical intermediary that facilitates bonding between the electrode and substrate through the insulating layer. During firing, this intermediary creates strong chemical bonds that penetrate the insulating layer, achieving both electrical connectivity and mechanical strength simultaneously without requiring layer removal
Solution Approach 2:
The conductive paste is formulated as a composite material containing conductive metal particles, fusible glass, and chemical etchants/fluorinated compounds. This composite structure enables multifunctional performance: electrical conductivity from metal particles, chemical penetration and bonding from etchants, and mechanical strength from the fusible glass matrix, resolving the contradiction between electrical connection and bond strength
3Manufacturing precision
If conventional paste composition is used, then manufacturing is simpler, but penetration of the insulating layer and formation of low-resistance contacts is insufficient
Solution Approach 1:
The patent precisely adjusts the composition parameters of the conductive paste, incorporating specific amounts of fluorinated compounds (0.1-5 wt%) or etchants (1-20 wt%) along with conductive metal particles and fusible glass. These parameter changes enable effective insulating layer penetration and low-resistance contact formation while maintaining manufacturability through a single-paste application process
Solution Approach 2:
The conductive paste is designed as a sophisticated composite material integrating conductive metal particles, fusible glass, and chemical reaction agents (fluorinated compounds or etchants). This composite formulation achieves superior penetration quality and contact resistance characteristics while preserving ease of manufacture through conventional 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 proposed paste composition improves the electrical and mechanical properties of photovoltaic cells by enabling effective penetration of insulating layers and forming low-resistance contacts, leading to higher conversion efficiency and stability of the solar cells.
Implementation Method 1
a fusible material... firing the pastes... dissolve or otherwise penetrate the insulating layer
Implementation Method 2
an organic medium... firing the pastes... sinter the metal powder
Data Source
AI summary
A conductive paste composition contains a source of an electrically conductive metal, a fusible material, a synthetic clay additive, and an optional etchant additive, dispersed in an organic medium. An article such as a photovoltaic cell is formed by a process having the steps of deposition of the paste composition on a semiconductor substrate by a process such as screen printing and firing the paste to remove the organic medium and sinter the metal and fusible material. The synthetic clay additive aids in establishing a low resistance electrical contact between the front side metallization and underlying semiconductor substrate during firing.