PROJECT PROFILE: Amtech Systems, Inc. (Incubator 10)

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Project Title: Efficiency Enhancement in c-Si Solar cells by Introducing Fixed-charge into SiNx Passivation Film Using a Novel Low-cost Plasma Charging Method
Funding Opportunity: SunShot Technology to Market (Incubator 10)
SunShot Subprogram: Technology to Market
Location: Tempe, Arizona
Amount Awarded: $930,664
Awardee Cost Share: $236,000
Project Investigator: Jeong-Mo (James) Hwang

Amtech is developing a low-cost field-effect passivation technology in partnership with Georgia Institute of Technology. It uses a novel, concept-proven method of charge introduction into a surface passivation film to improve the cell efficiency in advanced crystalline silicon (c-Si) solar cells and ultimately reduce the cost of the electricity generated. Its key objective is to optimize the technology including passivation film stacks and cell structures to maximize the charging effect and the charge reliability. This funding opportunity is expected to expedite the commercialization of the technology while introducing new equipment to the solar industry.

Approach

Aluminum oxide (Al₂O₃) passivation with Silicone Nitride (SiNx) capping layer has been introduced and used among passivation options for p-type surface passivation such as rear p-type in PERC and p+ emitter in n-PERT, because it contains a high density of negative charges and gives a good field-effect passivation. However, there are some inherent issues with this Al₂O₃ technology because it uses an explosive chemical precursor, TMA, such as a high cost of ownership and safety. This project uses a novel low-cost plasma charging method that can introduce not only negative charges without need of using an expensive Al₂O₃ process, but also positive charges for n-type surface passivation.  In this approach, a key concern for the commercialization the technology is the charge stability or reliability, which will be addressed by developing an optimum passivation stack and the best cell structure for the charging application.

Innovations

This new charging technology uses an inexpensive inert gas made of nitrogen or argon for plasma generation, which does not cause any parasitic film deposition, any corrosion inside the chamber, nor any safety or environmental issues. This clean process requires no regular tool maintenance for chamber cleaning, and can lower both capital and operation expenditures when compared to Al₂O₃ processes. Another advantage is that plasma charging works well on finished cells even with metal fingers and bus-bars, which allows manufacturers to add the charging process step at the end of the cell processing flow without any disturbance to an existing cell manufacturing line.