Conductive Paste for Solar Cell Electrodes
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Solution Overview
Problem
The existing methods for forming solar cell electrodes in crystalline silicon solar cells face challenges in reducing contact resistance and selecting appropriate glass frit compositions, leading to increased development costs and unclear guidelines for achieving low contact resistance.
Innovation Solution
A conductive paste comprising a conductive powder, a glass frit with specific oxidation states identified by X-ray photoelectron spectroscopy (XPS), and an organic vehicle, where the glass frit's XPS spectrum shows a signal intensity peak between 529 eV and 531 eV with a proportion of 40% or more, is used to form electrodes that can fire through antireflection films and achieve good solar cell characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional glass frit compositions are used in conductive pastes, then the electrode formation process is simple, but the contact resistance between electrode and n-type diffusion layer is high and solar cell characteristics are poor
Solution Approach 1:
The patent applies parameter changes by specifying precise compositional parameters for the glass frit (PbO: 40-70 wt%, Bi2O3: 10-30 wt%, B2O3: 5-20 wt%, SiO2: 5-20 wt%) to optimize the chemical properties of the conductive paste. This systematic parameter optimization enables the glass frit to effectively reduce contact resistance while providing clear selection criteria that actually simplifies the formulation process.
Solution Approach 2:
The patent employs composite materials by creating a multi-component glass frit system combining PbO, Bi2O3, B2O3, and SiO2 in specific proportions. This composite composition leverages the synergistic effects of different oxides: PbO for low melting point and wetting, Bi2O3 for reactivity with silicon, B2O3 for glass network formation, and SiO2 for structural stability, achieving superior contact resistance reduction compared to single-component systems.
2Reliability
If multiple types of glass frit with different oxide contents are tested to find optimal composition, then contact resistance can be reduced, but development costs and time increase
Solution Approach 1:
The patent applies preliminary action by establishing the optimal glass frit composition parameters in advance through systematic research and experimentation. By pre-determining the effective compositional ranges (PbO: 40-70 wt%, Bi2O3: 10-30 wt%, etc.), the patent provides ready-to-use formulation guidelines that eliminate the need for extensive trial-and-error testing during product development, significantly reducing development time while ensuring optimal contact resistance.
Solution Approach 2:
The patent incorporates feedback mechanisms by providing specific compositional parameters and performance criteria that allow manufacturers to immediately assess whether a glass frit formulation meets the required standards. The clearly defined oxide content ranges and their corresponding effects on contact resistance create a feedback loop where composition can be quickly adjusted and evaluated against known optimal parameters, accelerating the development process.
3Reliability
If glass frit with high PbO and Bi2O3 content is used, then contact resistance decreases, but the composition selection becomes more restricted and costly
Solution Approach 1:
The patent applies parameter changes by defining specific compositional ranges rather than fixed values, providing flexibility within optimized boundaries. The specified ranges (PbO: 40-70 wt%, Bi2O3: 10-30 wt%, B2O3: 5-20 wt%, SiO2: 5-20 wt%) allow manufacturers to adjust formulations based on material availability and cost considerations while maintaining the critical PbO-Bi2O3 combination necessary for low contact resistance, thus balancing performance requirements with compositional flexibility.
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
This approach provides guidelines for selecting glass frit compositions, reducing contact resistance, and enabling the production of solar cells with improved fill factor and conversion efficiency, thereby simplifying the development process and enhancing solar cell performance.
Implementation Method 1
During firing, the conductive paste fires through the antireflection film 2 with the result that the light incident-side electrode 1 comes to be in contact with then-type diffusion layer 3. Here, fire through is the etching of the insulating antireflection film with materials such as glass frits present in the conductive paste
Implementation Method 2
X-ray photoelectron spectroscopy of the glass frit gives a spectrum representing binding energies of oxygen
Data Source
AI summary
A process for producing conductive pastes for forming solar cell electrodes, including a step of measuring binding energies of oxygen in a glass frit by X-ray photoelectron spectroscopy, a step of selecting a glass frit providing an X-ray photoelectron spectrum representing binding energies of oxygen in which the signal intensity of a peak with a peak top at a range from 529 eV to less than 531 eV has a proportion of 40% or more relative to the total of signal intensities from 526 eV to 536 eV, and a step of mixing together a conductive powder, the glass frit and an organic vehicle.