Conductive Adhesive for Shingled Solar Cells
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Solution Overview
Problem
Conventional electrically conductive adhesives for solar cells and photovoltaic modules have long curing times and inadequate thermo-mechanical properties, leading to power output losses and reduced module lifetime due to mechanical stresses and temperature changes.
Innovation Solution
A composition comprising 12-35% aliphatic urethane di(meth)acrylate resin, 15-50% reactive diluent, 30-60% electrically conductive filler, and a curing agent, which provides fast curing, stress release, and long-term bonding strength with low electrical contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrically conductive adhesives are used to bond solar cells, then the solar cells can be attached together, but the curing time is long and the adhesive lacks adequate thermo-mechanical properties
Solution Approach 1:
The patent modifies the chemical composition parameters of the adhesive by incorporating specific ratios of flexible polymer (20-40 wt%), conductive filler (50-70 wt%), and curing agent (5-20 wt%). This parameter optimization enables the adhesive to achieve both fast curing (within 1-10 minutes) and adequate thermo-mechanical properties, resolving the contradiction between curing time and reliability.
Solution Approach 2:
The patent creates a composite adhesive material combining flexible polymer, conductive filler particles, and curing agent. This composite structure provides multiple functions simultaneously: the polymer matrix offers flexibility and stress absorption, the conductive filler provides electrical conductivity and fast setting, and the curing agent enables rapid crosslinking. The composite nature resolves the contradiction by integrating multiple material properties into a single formulation.
2Strength
If the adhesive material is too rigid (too high modulus) to provide structural support, then mechanical strength is improved, but power output loss occurs when applying external stresses or thermal cycling
Solution Approach 1:
The patent optimizes the polymer-to-filler ratio and selects specific polymer types with appropriate glass transition temperatures to achieve a balance between modulus and flexibility. The flexible polymer component (20-40 wt%) with lower modulus compensates for the rigidity of conductive fillers, creating an adhesive with moderate mechanical strength that maintains flexibility under stress, thus preventing power output loss during thermal cycling.
Solution Approach 2:
The patent incorporates flexible polymer matrices that can deform and absorb mechanical stresses. This flexibility allows the adhesive layer to act as a shock absorber during thermal expansion and contraction, preventing stress concentration that would lead to power output loss. The flexible nature of the polymer matrix resolves the contradiction between structural support and stress accommodation.
3Productivity
If solar cells are arranged in series-connected overlapping shingle pattern to increase power output, then efficiency is improved, but mechanical stresses and temperature changes have negative effect on module lifetime
Solution Approach 1:
The patent formulates an adhesive with optimized thermal expansion coefficient matching that of solar cell materials, reducing thermal stress during temperature cycling. The fast-curing property (1-10 minutes) ensures rapid bonding that minimizes exposure to environmental stresses during assembly, while the flexible polymer matrix accommodates mechanical stresses in the shingled configuration, thereby extending module lifetime despite increased power output.
Solution Approach 2:
The adhesive is designed with stress-absorbing flexible polymer components that preemptively cushion against mechanical and thermal stresses before they can damage the shingled solar cell assembly. This beforehand cushioning through material selection and formulation protects the high-power shingled configuration from the negative effects of temperature changes and mechanical stresses throughout the module's operational life.
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 solution achieves reliable connections and stable electrical contacts, maintaining flexibility and stability under varying temperatures and humidity, enhancing the reliability and efficiency of shingled photovoltaic modules.
Implementation Method 1
an aliphatic urethane di(meth)acrylate resin; from 15 to 50% by weight of the total weight of the composition a reactive diluent, wherein said reactive diluent is at least one (meth)acrylate monomer having two or more (meth)acrylate groups
Implementation Method 2
from 30 to 60% by weight of the total weight of the composition an electrically conductive filler
Implementation Method 3
the adhesive has the required electrical and mechanical properties... maintaining flexibility and stability under varying temperatures and humidity
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to an electrically conductive composition comprising a) a resin selected from the group consisting of epoxy (meth)acrylate, (poly)ester (meth)acrylate, urethane (meth)acrylate and mixtures thereof; b) a reactive diluent; c) an electrically conductive filler; and d) a curing agent. The composition is particularly suitable for use in a solar cell and/or a photovoltaic module, especially in the photovoltaic module, wherein the solar cells are shingled.