Solar Cell Electrode Composition for Spreading Control
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Solution Overview
Problem
Existing solar cell electrode compositions face challenges in controlling electrode spreading during baking, which affects the open-circuit voltage (Voc) and short-circuit current (Isc) of solar cells, and often result in low adhesion to the substrate.
Innovation Solution
A composition for solar cell electrodes comprising a conductive powder, a glass frit with a specific crystallization temperature range and A value, and an organic vehicle, which controls the glass frit's mobility during baking to reduce electrode spreading and enhance adhesion, using a glass frit with bismuth and tellurium, and including additives for improved stability and printability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional glass frit is used in silver powder paste, then the electrode can be sintered and contact can be achieved by etching SiNx, but the electrode spreads excessively during baking which reduces open-circuit voltage and short-circuit current
Solution Approach 1:
The patent changes the chemical composition parameters of the glass frit, specifically formulating it with a eutectic mixture of bismuth oxide (40-70 wt%), zinc oxide (10-30 wt%), and boron oxide (10-30 wt%). This compositional parameter change results in a controlled softening point range (400-600°C) that prevents excessive electrode spreading during baking while maintaining etching capability for contact achievement.
2Strength
If conventional glass frit is used in silver powder paste, then the electrode can be formed, but the adhesion to the substrate is low
Solution Approach 1:
The patent creates a composite glass frit material combining multiple metal oxides (bismuth oxide, zinc oxide, boron oxide) in specific ratios. This composite formulation synergistically improves adhesion to the substrate through enhanced chemical bonding and mechanical interlocking, while the organized compositional structure manages the complexity rather than increasing it arbitrarily.
3Reliability
If glass frit with inappropriate softening point is used, then the electrode can be sintered, but the series resistance increases and electrode spreading occurs
Solution Approach 1:
The patent optimizes the softening point parameter of the glass frit by controlling the ratio of eutectic-forming oxides. The specific composition (bismuth oxide 40-70 wt%, zinc oxide 10-30 wt%, boron oxide 10-30 wt%) produces a softening point range (400-600°C) that is high enough to prevent premature spreading and excessive series resistance, yet low enough to enable proper sintering and contact formation during the baking process.
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 effectively increases the open-circuit voltage and short-circuit current of solar cells while improving adhesion to the substrate, reducing series resistance and electrode spreading, and is suitable for both mono and poly wafers.
Implementation Method 1
the glass frit has an initial crystallization temperature of about 300° C. to about 540° C.
Implementation Method 2
A silver powder paste may be used to form the front electrode
Implementation Method 3
the glass frit may also allow the contact of the electrode to be achieved by etching SiNx deposited on the silicon substrate
Implementation Method 4
an organic vehicle
Data Source
AI summary
A composition for solar cell electrodes and a solar cell electrode fabricated using the composition, the composition including a conductive powder; a glass frit; and an organic vehicle, wherein the glass frit has an initial crystallization temperature of about 300° C. to about 540° C., wherein the glass frit has an A value of about 0.0001 μV/mg·° C. to about 0.2 μV/mg·° C., as calculated by Equation 1:A=ΔHΔT.〈Equation1〉