Selenium Glass Frit Conductive Paste for Controlled Passivation Etching
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Solution Overview
Problem
Current conductive metal pastes used in crystalline silicon solar cells have challenges in achieving a balance between electrical contact resistance and carrier recombination due to the high glass transition temperature of lead-boron-silicon glass frits, which can lead to inadequate etching and excessive carrier recombination.
Innovation Solution
A conductive paste composition is developed using a lead-boron-selenium glass frit, which replaces the traditional lead-boron-silicon glass frit, along with a conductive component and an aluminum elemental component, to form a low-resistance electrical contact with p-type semiconductors in n-type crystalline silicon solar cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If lead-boron-silicon glass frit is used in conductive metal paste, then the paste can provide basic etching capability, but the high glass transition temperature results in inadequate etching and excessive carrier recombination
Solution Approach 1:
The patent changes the chemical composition parameters of the glass frit by replacing silicon oxide with selenium oxide, which fundamentally alters the glass transition temperature from high to low, enabling adequate etching at lower temperatures and preventing excessive carrier recombination
Solution Approach 2:
The patent creates a composite glass frit system combining lead oxide, boron oxide, and selenium oxide, where the synergistic interaction between these components achieves both low glass transition temperature and controlled etching capability, resolving the contradiction between temperature and etching precision
2Temperature
If boron content is reduced to lower glass transition temperature, then the Tg point decreases, but the glass frit becomes difficult to maintain amorphous state and crystallizes easily
Solution Approach 1:
The patent changes the compositional parameters by introducing selenium oxide as a key component, which provides low-temperature glass formation characteristics while maintaining amorphous state stability, eliminating the need to reduce boron content
Solution Approach 2:
Selenium oxide acts as an intermediary component that mediates between the conflicting requirements of low glass transition temperature and amorphous state stability, enabling the glass frit to achieve both properties simultaneously through its unique chemical characteristics
3Temperature
If alkali metal, alkaline earth metal, or rare earth metal content is increased to reduce glass transition temperature, then the Tg point decreases, but photovoltaic device efficiency is affected due to high corrosivity
Solution Approach 1:
The patent changes the chemical composition by using selenium oxide instead of increasing alkali/alkaline earth/rare earth metals, achieving low glass transition temperature through a different chemical mechanism that does not involve high corrosivity
Solution Approach 2:
The patent converts the potential harm of aggressive etching into a benefit by using selenium oxide, which provides sufficient etching capability at lower temperatures without the excessive corrosivity that would damage the photovoltaic device and reduce efficiency
4Temperature
If thallium is added to reduce glass transition temperature, then the Tg point decreases effectively, but the paste becomes highly toxic and harmful to the environment
Solution Approach 1:
The patent replaces the highly toxic thallium with selenium oxide, which achieves the same glass transition temperature reduction effect without the severe toxicity and environmental harm, converting a harmful solution into a beneficial one
Solution Approach 2:
The patent changes the toxicological parameters of the glass frit composition by substituting thallium with selenium oxide, maintaining the functional parameter of low glass transition temperature while dramatically improving the safety and environmental compatibility parameters
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 new conductive paste composition achieves a decent fill factor and photoelectric conversion efficiency by controlling the etching of the passivation film and forming a low-resistance electrical contact, while also being free from highly toxic elements like thallium, reducing environmental harm and facilitating recycling.
Implementation Method 1
the lead-boron-selenium glass frit...is used to etch the passivation film in the n-type crystalline silicon solar cell to form the electrical contact with the p-type semiconductor
Implementation Method 2
form a low-resistance ohmic contact
Data Source
AI summary
A conductive paste composition, a preparation method and a use thereof, as well as a crystalline silicon solar cell are disclosed. The conductive paste composition contains a silver powder and an aluminum powder, and contains a lead-boron-selenium glass frit or a bismuth-boron-selenium glass frit. The conductive paste composition can perform effective etching of a passivation film of an n-type crystalline silicon solar cell during a high temperature firing, and also does not over-oxidize the aluminum powder contained therein, thereby forming an electrode having decent electrical contact with a p-type doped emitter.