Conductive Paste Composition for Solar Cell Electrodes
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Solution Overview
Problem
Conventional conductive paste compositions for photovoltaic devices face challenges in forming high-quality electrodes with low resistance and strong adhesion, while minimizing shadowing and maintaining electrical efficiency, as they often result in excessive line spreading and residue from organic vehicles during firing.
Innovation Solution
A conductive paste composition comprising an inorganic solids portion with a source of electrically conductive metal and an oxide-based component dispersed in a vehicle containing microgel particles, organopolysiloxane, and solvent, which promotes the formation of high-conductivity electrodes with low resistance and strong adhesion to the substrate, and facilitates firing through insulating layers without residue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive paste compositions are used to form electrodes, then the electrodes can be created with basic conductivity, but the organic vehicle leaves residue during firing that degrades electrical performance
Solution Approach 1:
The patent changes the chemical composition parameters of the vehicle from conventional organic solvents to a specific formulation containing diethylene glycol dibutyl ether, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, and ethyl cellulose. This parameter change eliminates harmful residue during firing while maintaining paste applicability and electrode conductivity.
Solution Approach 2:
The patent uses ethyl cellulose as a sacrificial binder that completely decomposes and evaporates during the firing process, leaving no harmful residue. This disposable organic component serves its purpose during application and then is completely eliminated in the high-temperature firing, replacing persistent harmful organic vehicles.
2Reliability
If conventional paste compositions are fired to create electrodes, then conductive structures are formed, but excessive line spreading occurs that increases shadowing and reduces efficiency
Solution Approach 1:
The patent replaces mechanical adhesion mechanisms with chemical bonding mechanisms. The specific solvent formulation creates controlled chemical interactions during firing that prevent excessive lateral spreading of the conductive paste, maintaining precise line patterns while forming strong bonds to the substrate.
Solution Approach 2:
The patent uses a composite vehicle formulation combining multiple solvents (diethylene glycol dibutyl ether and 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate) with ethyl cellulose. This composite material provides both controlled rheology during application to prevent spreading and appropriate reactivity during firing to form precise conductive patterns.
3Ease of manufacture
If conventional paste compositions are applied to create fine conductive lines, then the paste can be deposited, but the organic polymer vehicle creates residue that degrades electrode quality
Solution Approach 1:
The patent changes the molecular weight and chemical structure parameters of the organic vehicle components. Ethyl cellulose with specific molecular weight characteristics provides adequate viscosity for screen printing application, then completely decomposes at firing temperatures without leaving degrading residue, unlike conventional high molecular weight organic polymers.
Solution Approach 2:
The patent applies the principle of local quality by having the vehicle serve different functions at different stages: during application, it provides appropriate viscosity and flow characteristics for screen printing; during firing, it completely decomposes without residue. This localized functional optimization resolves the contradiction between ease of manufacture and harmful residue.
4Productivity
If conventional conductive paste is used to minimize shadowing, then fine line patterns are required, but line spreading during firing increases the shadowed area and reduces photovoltaic efficiency
Solution Approach 1:
The patent replaces mechanical confinement methods with chemical control mechanisms. The specific solvent-paste interaction chemistry creates controlled sintering behavior during firing that maintains narrow line widths without requiring excessive mechanical confinement, thereby minimizing shadowing while ensuring complete firing through the anti-reflective layer.
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 fabrication of electrodes with improved electrical and mechanical properties, including high photovoltaic conversion efficiency, low series resistance, and good mechanical adhesion, while minimizing line spreading and shadowing, thereby enhancing the overall performance of photovoltaic devices.
Implementation Method 1
firing the semiconductor substrate and the paste composition under conditions sufficient to form an electrode in electrical contact with the semiconductor substrate
Data Source
AI summary
The present invention provides a thick-film paste composition for printing the front side of a solar cell device having one or more insulating layers. The thick-film paste comprises an electrically conductive metal and an oxide composition dispersed in an organic medium that includes microgel particles and an organopolysiloxane.