Solar Cell Electrode Intermediate Layer for Low Contact Resistance
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Solution Overview
Problem
The existing solar cell manufacturing methods face challenges with high manufacturing costs due to the use of expensive conductive silver paste, increased surface recombination rates, and high contact resistance between finger and bus bar electrodes, particularly in PR structure-type solar cells.
Innovation Solution
Incorporating an intermediate layer formed by baking conductive silver paste between aluminum finger electrodes and bus bar electrodes formed using low-temperature thermosetting silver paste, reducing contact resistance and surface recombination rates while maintaining low manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive silver paste is used to form finger electrodes, then contact resistance is reduced, but manufacturing cost increases
Solution Approach 1:
The electrode system is segmented into three functional layers: aluminum finger electrodes for substrate contact, intermediate silver-containing paste layers for low-resistance connections, and silver bus bar electrodes for current collection. This segmentation allows each layer to be optimized for its specific function, using inexpensive aluminum where cost matters most while applying expensive silver only where low resistance is critical.
Solution Approach 2:
Different materials are applied locally to different regions of the electrode system based on functional requirements. Aluminum paste is used in contact sections with the substrate where cost reduction is prioritized, while silver-containing paste is applied at intersection points with bus bar electrodes where low contact resistance is prioritized.
2Ease of manufacture
If conductive aluminum paste is used to form finger electrodes, then manufacturing cost is reduced, but contact resistance between finger electrodes and bus bar electrodes increases
Solution Approach 1:
An intermediate layer containing silver paste and glass frit is introduced between the aluminum finger electrodes and silver bus bar electrodes. This intermediate layer acts as a mediator that chemically and electrically bridges the aluminum and silver, enabling low-contact-resistance connections while allowing the use of inexpensive aluminum for the finger electrodes.
Solution Approach 2:
The intermediate paste layer is formulated as a composite material containing both silver particles (for electrical conductivity) and glass frit (for adhesion and penetration). This composite structure provides both low electrical resistance and strong bonding between the aluminum finger electrode and silver bus bar electrode.
3Reliability
If conductive silver paste is used to form bus bar electrodes, then connection quality is improved, but manufacturing cost increases
Solution Approach 1:
The electrode system is segmented into three functional layers: aluminum finger electrodes for substrate contact, intermediate silver-containing paste layers for low-resistance connections, and silver bus bar electrodes for current collection. This segmentation allows each layer to be optimized for its specific function, using inexpensive aluminum where cost matters most while applying expensive silver only where low resistance is critical.
4Reliability
If electrodes penetrate the passivation film, then contact resistance with substrate is reduced, but surface recombination rate increases
Solution Approach 1:
Different electrode materials and structures are applied locally to different regions: aluminum paste with p+ layer formation for finger electrode contacts where penetration is needed, and silver paste without penetration for bus bar electrodes where surface recombination must be minimized.
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 enables the production of solar cells with improved conversion efficiency and reduced manufacturing costs by effectively connecting finger and bus bar electrodes at low resistance, thereby enhancing the solar cell's performance and yield.
Implementation Method 1
During the baking of the conductive aluminum paste, a p+ layer is formed in a contact section of the substrate and the conductive aluminum paste
Implementation Method 2
as a method of forming the bus bar electrode, it is desirable to use a method of printing low-temperature thermosetting silver paste and thereafter drying and heating the low-temperature thermosetting silver paste to connect the low-temperature thermosetting silver paste to only the finger electrodes
Implementation Method 3
Incorporating an intermediate layer formed by baking conductive silver paste between aluminum finger electrodes and bus bar electrodes formed using low-temperature thermosetting silver paste
Data Source
AI summary
An object of the present invention is to provide, at a low cost, a system and a method for manufacturing a solar cell having high conversion efficiency. A solar cell according to the present invention is characterized by including a passivation film that protects a semiconductor substrate, a first finger electrode connected to the semiconductor substrate on a main surface of the semiconductor substrate, a first bus bar electrode that intersects the first finger electrode, and an intermediate layer provided in an intersecting position of the first finger electrode and the first bus bar electrode. The solar cell is characterized in that the first finger electrode and the first bus bar electrode are electrically connected to each other via the intermediate layer.