Sunbox silane free coating system

DESCRIPTION

Anti-reflective (AR) coating deposition is a critical step in every c-Si solar cell manufacturing facility. Without AR coating, solar cells would suffer losses as high as 40% in conversion efficiency.

Over the past few years, silane-based silicon nitride deposition has become the process of choice for AR coatings because of its favorable AR and surface passivation qualities. However, incorporating silicon nitride deposition into the process flow introduces significant amounts of pyrophoric silane gas. Despite extensive study by industry, the precise behavior of silane gas during a leak is unpredictable and often results in fires and explosions. Silane incidents can also lead to significant production downtime. With high volume cell fabs producing over one million cells per day, a single silane incident can result in millions of dollars in losses. Since a silane explosion and resulting worker fatalities occurred at a major solar cell production facility in 2005, the solar industry has been looking for a reliable and practical alternative for high performance AR and passivation coatings.

Today, almost 90% of SiNx AR deposition systems use silane gas to generate AR and passivation coatings. Users of such equipment are required to construct specialized containment equipment, maintain extensive safety protocols and pay for premium delivery procedures. Sometimes called the “silane tax,” the large safety and infrastructure expenses associated with silane reduce profit margins and ultimately present a barrier to further cost reduction in solar. Additionally, any malfunctions or mishaps during frequent replacements of silane cylinders can completely shut down or halt entire production facilities for days or even months.  In this way, the efficiency benefits associated with silicon nitride coatings are partially offset by the high capital and operational expenditures associated with the risks of silane.

Sixtron is the first company to provide a PECVD-based AR and passivation coating system that delivers the performance of today’s silicon nitride coatings without the use of silane gas. Known as the SunBox, the system’s core technology is based upon a unique solid polymer source material that is safe to handle, ship and store—a stark contrast to the costs and dangers of silane.

INNOVATIVE ASPECT

The essence of Sixtron’s innovation is in turning one of the most dangerous and costly steps in solar cell production into a simple, safe and cost-effective process.

The SunBox on-site gas generation system deposits high performance AR and passivation coatings by gasifying an inert solid polymer source material. The gas is then piped into a standard plasma enhanced chemical vapor deposition (PECVD) reactor to form a silicon carbonitride (SiCN) AR and passivation coating that matches, and potentially exceeds, the performance of today’s silane-based SiNx coatings.

Designed as a drop-in replacement for the silane supply, the SunBox system integrates with the same PECVD systems in today’s multi- and mono-crystalline solar cell manufacturing lines. Additionally, the SunBox systems is connected and monitored with standard piping and mass flow controllers, allowing manufacturers to integrate the SunBox without purchasing new or specialized equipment.

The unique programmable nature of the on-site gas generation system allows manufacturers to develop optimized chemical compositions and even entirely new kinds of passivation layers, such as multi-layer graded refractive index coatings.  In addition, leading research institutions, such as Georgia Tech, IMEC and the University of Konstanz, are working with Sixtron to examine the potential for the SunBox to also apply backside passivation coatings.

BENEFITS

The large volumes of silane gas required in today’s solar cell manufacturing processes is impeding cost reduction for the industry. Sixtron is removing this limitation. The SunBox drives higher product margins and reduces company-wide risk by replacing hazardous and costly silane-based coating components with silane-free technology that improves overall fab reliability, efficiency and safety.

With the SunBox, PV manufacturing has lower associated risks, smaller capital expenditures and reduced operating costs.  Specifically, Sixtron drives:

• Up to 50% reduction in installation cost of AR coating systems for new manufacturing lines
• Up to 50% reduction in total operating cost of AR coating systems
• Reduced maintenance costs for auxiliary equipment and pumps due to elimination of silane byproducts