Solar Cell Electrode Paste Composition for Ultra-Thin Emitter Control
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Solution Overview
Problem
The manufacturing process for ultra-thin silicon solar cells faces challenges in forming emitters with high sheet resistance, which can lead to short circuits due to excessive firing during the formation of electrodes, necessitating an electrode paste that can control penetration and maintain the quality of the emitter layer.
Innovation Solution
A solar cell electrode paste comprising silver (Ag) and zinc (Zn) with a lead-free glass frit and resin binder, applied in a specific composition ratio to control the depth of the emitter layer, allowing for precise contact with the semiconductor substrate and preventing short circuits, while also forming a rear electrode that penetrates through a dielectric layer to contact the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrode paste is used to form front electrode on ultra-thin emitter, then electrode formation is achieved, but excessive firing causes penetration through the thin emitter layer leading to short circuits
Solution Approach 1:
The paste composition parameters are changed by incorporating specific glass frit materials and adjusting metal particle size distribution to control the firing behavior. This modifies the melting temperature and viscosity characteristics of the paste, enabling precise control over penetration depth to match the ultra-thin emitter thickness without causing short circuits
Solution Approach 2:
Glass frit acts as an intermediary material that controls the interaction between the metal particles and the semiconductor substrate during firing. The glass frit matrix regulates the softening and penetration process, preventing direct excessive contact between metal particles and the thin emitter layer, thereby avoiding short circuits while maintaining electrical contact
2Productivity
If emitter layer thickness is reduced to ultra-thin for high efficiency, then photovoltaic efficiency is improved, but control over firing penetration becomes difficult
Solution Approach 1:
Multiple paste parameters are optimized including glass frit composition (lead-free formulations), metal particle size distribution (bimodal or multimodal distributions), and organic vehicle content to achieve controlled firing behavior on ultra-thin emitters while maintaining high photovoltaic efficiency
Solution Approach 2:
The electrode paste is formulated as a composite material system combining metal particles (silver, aluminum, or their alloys), glass frit (lead-free compositions with specific softening points), and organic binders. This composite structure enables independent optimization of electrical conductivity, penetration control, and adhesion properties for ultra-thin emitter applications
3Object-affected harmful factors
If lead-free glass frit is used in electrode paste, then environmental compliance is achieved, but paste formulation complexity increases
Solution Approach 1:
The glass frit composition parameters are changed from lead-based to lead-free formulations, utilizing alternative oxides (such as bismuth oxide, barium oxide, or zinc oxide) to achieve similar or improved softening characteristics and rheological properties without the harmful effects of lead
Solution Approach 2:
The patent employs conventional, well-established lead-free glass frit materials that are commercially available and cost-effective, avoiding the need for proprietary or complex formulations. These materials provide sufficient performance for the application without requiring overly complicated paste designs
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 electrode paste enhances the photovoltaic efficiency of high sheet resistance (High Rs) solar cells by minimizing the dead layer and ensuring proper contact, thereby improving the overall efficiency and manufacturing feasibility of ultra-thin solar cells.
Implementation Method 1
heat-treating the front electrode paste thereby causing a resulting front electrode to penetrate through the antireflective layer and make contact with the semiconductor layer
Implementation Method 2
a second component including zinc (Zn)... where the composition of the front electrode paste limits the penetration of the front electrode to the semiconductor layer
Data Source
AI summary
An electrode paste for a solar cell, a solar cell electrode using the paste, a solar cell having such an electrode, and a fabrication method of the solar cell are described. The paste for a solar cell electrode comprises a first component that includes silver (Ag) or a metal alloy containing the silver (Ag); a second component that includes zinc (Zn), and at least one selected from a group consisting of silicon (Si), aluminum (Al), copper (Cu), manganese (Mn), bismuth (Bi), phosphorous (P), boron (B), barium (Ba), and palladium (Pd); a leaded or lead-free glass frit; and a resin binder that is dispersed in an organic medium.