The use of plasma surface modification technology in photovoltaic cell manufacturing has heretofore been used primarily in applications such as the deposition of amorphous hydrogenated silicon nitride (SiN) layers in a vacuum plasma-enhanced chemical vapor deposition (PECVD) process to create anti-reflection and surface (and bulk) passivation on thin-film solar cells, or the use of vacuum plasma etching in barrel-type reactors to perform edge isolation in some remaining fabrication processes. As photovoltaic cell manufacturing processes evolve, and with the added pressures of increasing hazardous chemical waste disposal costs, there has been interest in atmospheric plasma systems as efficient dry etching, surface cleaning and adhesion promotion process tools. This paper examines these systems and details etching, cleaning and bonding trial data confirming system efficacies.
Introduction
The use of plasmas in the fabrication of photovoltaic cells is highly dependent upon the materials employed and the processing cycle requirement. For example, vacuum plasmas are not suitable for use in solar cell processing when high throughput on a continuous basis is required. Vacuum plasma chambers built for SiNx deposition are typically batch process related, but are also designed to work in a semi -continuous mode through the intermittent exchange of treatment materials within the vacuum chamber after the treatment is completed and one atmospheric pressure is returned. However, this process is still not economical for high throughput plasma surface etching, cleaning and functionalization.
Considering the wide range of materials employed to maximize solar efficiencies, the ability to integrate the completely continuous in-line manufacturing of rigid panel and flexible solar cells by utilizing a variable chemistry surface modification technique relative to complex material constructions holds the prospect of significantly reducing manufacturing costs.
Atmospheric pressure gas phase plasma technology is highly effective at treating: Aluminum, Copper, Stainless Steel, EVA Film, ITO Film, PEN Film, PET Film, Polyimide Film, and Glass.
Plasma3™ will therefore become essential for future in-line manufacturing of solar cells if major reductions in fabrication costs are to be achieved.
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