SAM Interface Layer for Narrower Photovoltaic Metal Lines
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Solution Overview
Problem
The inkjet process for metallization in photovoltaic cell manufacturing faces challenges in forming a conductive metal layer of sufficient quality on transparent conductive oxide layers due to the properties of silver inks and the substrate, leading to issues with ink spreading and line width control.
Innovation Solution
A self-assembled molecular monolayer (SAM) is introduced as an interface layer between the transparent conductive oxide and the metallic conductive layer, which modifies the surface energy and improves inkjet printing by reducing the spreading of metallic ink, allowing for smaller metal wire sizes without impacting electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If inkjet printing is used to deposit metallic conductive material onto TCO layer, then thermal stress and mechanical stress are reduced compared to screen printing, but the ink spreading becomes difficult to control due to low viscosity of inks and predominant role of surface energy
Solution Approach 1:
A self-assembled monolayer (SAM) is introduced as an intermediary layer between the TCO substrate and the metallic ink. This SAM layer modifies the surface energy of the TCO, creating optimal wetting conditions that control ink spreading. The SAM acts as a mediator that enables the low-viscosity ink to be deposited with precise line width control while maintaining the thermal and mechanical stress advantages of inkjet printing.
Solution Approach 2:
The surface energy parameter of the TCO substrate is changed by coating it with a self-assembled monolayer. This parameter modification transforms the substrate surface from high energy to low energy, which directly controls the wetting behavior and spreading of the metallic ink during inkjet deposition, enabling precise line width control.
2Reliability
If sufficient quantity of metallic material is deposited to guarantee low line resistance, then optimal current collection is achieved, but the width of lines increases causing performance losses due to shading
Solution Approach 1:
By changing the surface energy parameter of the substrate through SAM coating, the ink spreading is controlled to achieve narrower line widths. This allows sufficient metallic material to be deposited in a more concentrated manner, maintaining low line resistance and optimal current collection while reducing the overall line width to minimize shading losses on the active cell area.
Solution Approach 2:
The conventional screen printing mechanical process is replaced with inkjet printing, which uses a different deposition mechanism (droplet ejection and controlled spreading) that allows for more precise control of material distribution. Combined with SAM surface modification, this substitution enables achieving the same electrical performance with narrower lines.
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 SAM layer significantly reduces the surface energy of the substrate, enabling the formation of narrower metal lines with equivalent electrical properties, enhancing the efficiency of the metallization process in photovoltaic cells.
Implementation Method 1
said interface layer being a self-assembled molecular monolayer, referred to as SAM
Implementation Method 2
a specific chemical modification of the face of the transparent conductive oxide layer dedicated to being in contact with a metallic conductive layer, makes it possible to significantly reduce its surface energy
Implementation Method 3
the inkjet process... by projecting drops at speeds of several meters per second
Implementation Method 4
the heat treatments required to achieve low resistivities are significantly reduced
Data Source
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AI summary
The present invention relates to a multilayer structure comprising a photoelectric substrate, at least one transparent conductive oxide layer, referred to as "TCO" and at least one metallic conductive layer dedicated to forming an electrode characterized in that said structure further has at least one interface layer in contact with said transparent conductive oxide layer and said metallic conductive layer, said interface layer being a self-assembled molecular monolayer, referred to as SAM.