Conductive Paste Composition for Low-Resistance Photovoltaic Contacts
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Solution Overview
Problem
Conventional photovoltaic cells face challenges in achieving high electrical performance due to high dopant concentrations in emitters, which lead to recombination losses and poor metal contact formation, especially with lightly doped emitters, requiring a paste that can form low resistance contacts without damaging the emitter layer and minimizing series resistance.
Innovation Solution
A conductive paste composition comprising a source of electrically conductive metal, boron lithium tellurium oxide, and an organic vehicle, which penetrates insulating layers and forms robust, low-resistance contacts with the substrate, suitable for both heavily and lightly doped emitters, and enables the formation of high-aspect-ratio contact lines to reduce shading and series resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high dopant concentrations are used in emitters to improve metal contact formation, then contact quality improves, but recombination losses increase and electrical performance deteriorates
Solution Approach 1:
The invention changes the chemical composition parameters of the glass frit by incorporating specific metal oxides (Bi2O3, PbO, ZnO, B2O3, SiO2) in optimized ratios. This compositional modification alters the melting behavior and chemical reactivity of the glass frit, enabling it to form low-resistance contacts with lightly doped emitters without requiring high dopant concentrations that would cause recombination losses.
Solution Approach 2:
The conductive paste is formulated as a composite material combining conductive metal particles (silver, aluminum, or copper) with a specially designed glass frit matrix containing multiple metal oxides. This composite structure provides both the electrical conductivity needed for contact formation and the chemical properties required to penetrate and bond with the semiconductor substrate at lower dopant concentrations.
2Reliability
If conventional glass frit is used to penetrate insulating layers, then contact formation is achieved, but series resistance increases and electrical performance is limited
Solution Approach 1:
The glass frit composition is modified by adjusting the ratios of metal oxides (increasing Bi2O3 to 30-70 wt%, PbO to 5-40 wt%, and adding ZnO at 5-30 wt%) to optimize melting temperature and chemical reactivity. These parameter changes enable the glass frit to more effectively penetrate the silicon nitride insulating layer and form lower resistance contacts, reducing series resistance and improving overall electrical performance.
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 paste composition enhances photovoltaic cell performance by increasing open-circuit voltage and short-circuit current, achieving high conversion efficiency and fill factor while maintaining low series resistance and good adherence to the substrate.
Implementation Method 1
The front-side conductive metal paste typically includes a glass frit and a conductive species (e.g., silver particles) carried in an organic medium that functions as a vehicle for printing. The electrode may be formed by depositing the paste composition in a suitable pattern (for instance, by screen printing) and thereafter firing the paste composition and substrate to dissolve or otherwise penetrate the insulating anti-reflective layer and sinter the metal powder
Implementation Method 2
a conductive paste composition comprising a source of electrically conductive metal, boron lithium tellurium oxide, and an organic vehicle
Implementation Method 3
thereafter firing the paste composition and substrate to dissolve or otherwise penetrate the insulating anti-reflective layer and sinter the metal powder, such that an electrical connection with the semiconductor structure is formed
Data Source
AI summary
A conductive paste composition contains a source of an electrically conductive metal, a boron lithium tellurium oxide, and an organic vehicle. An article such as a high-efficiency photovoltaic cell is formed by a process of deposition of the paste composition on a semiconductor device substrate (e.g., by screen printing) and firing the paste to remove the organic vehicle and sinter the metal and establish electrical contact between it and the substrate.