Technical Papers

Efficient management of the PV supply chain can save a company money, both directly by reducing material and component cost, and indirectly by improving lead time, inventory optimization and quality throughout the entire value chain. So-called static supply chains compare poorly to their dynamic counterparts that see cost reduction and quality as well as material availability improvements. What follows is a proposal of improving the supply chain using methods like integration, data exchange and collaboration that can also help to improve entire E2E flows through re-structuring and outsourcing from one level to another.

Wet processing can be a very high performing and cost-effective manufacturing process. It is therefore extensively used in Si solar cell fabrication for saw damage removal, surface texturing, cleaning, etching of parasitic junctions and doped oxide glass. PV manufacturers have succeeded in bringing down the cost of ownership of batch-type and in-line tools. The trend to back-side passivated solar cells requires cost-effective single-sided processing solutions. With the future pointing to ever-thinner silicon solar cells, handling these thin wafers in wet environments is a major challenge for any wet process. This paper reviews the major wet processing steps, emphasising some new developments and unknown issues, and provides a more general outlook on trends in wet processing.

At First Solar’s corporate headquarters in Tempe, Arizona, a morale-boosting slogan adorns posters stuck to the outside of cubicle partitions: “MILESTONE MADE! TEN ONE ONE.” That’s “Ten,” for 10 years in business - at least in the company’s First Solar incarnation. The original firm Glasstech Solar, led by visionary Harold McMaster, actually set up shop in 1984, then became Solar Cells, Inc. in 1992, which begat the present entity in 1999. The middle “One” stands for the gigawatt’s worth of panels produced in the solar module factories in Ohio, Germany, and Malaysia - as well as the annual production capacity that will be ramped by the end of 2009. The final “One” stands for perhaps the biggest accomplishment of all - the dollar-per-manufactured-watt standard beaten by two cents by First Solar in the final quarter of 2008, a cost that has since shrunk to 93 cents per watt in the first quarter of 2009. But then, “Ten/One/0.93” doesn’t quite have the same ring.

A variety of thin-film technologies are now entering a volume manufacturing phase. The benchmark has already been set by First Solar, Inc. in its conversion efficiencies, volume ramp and lowest cost-per-watt in the PV industry. Large-area thin-film deposition is a critical process step, dictating cell performance, reliability and manufacturing throughput. However, adoption of thin-film solar cells has been limited in the past by relatively complex and costly manufacturing processes. The advent of rotating cylindrical magnetrons for sputtering is demonstrating the potential to significantly reduce thin-film manufacturing costs. In this paper we discuss the basics of the technology and the developments taking place with some of the leading suppliers of sputtering target technology for the PV industry.

Despite over 30 years of unprofitability, being viewed as too expensive and in many cases, unattractive, the PV industry has also enjoyed over 30 years of strong growth. Though granted, in the past, this growth was often from a much smaller base than the gigawatt levels experienced today, it is still an impressive achievement. Table 1 provides a history of PV industry growth from 1978 to the present. The data in Table 1 is based on what was sold into the global market to the first point of sale, eliminating double shipment (sales) of technology.

In 2008, the global PV market reached 5.6GW and the cumulative PV power installed totalled almost 15GW compared to 9GW in 2007. Spain represented almost half of the new installations in 2008 with about 2.5GW, followed by Germany with 1.5GW additional connected systems. USA confirmed its trend with 342MW newly installed PV systems, followed by South Korea which registered 274MW of PV installations over the year. Italy connected almost 260MW while France, Portugal, Belgium and the Czech Republic made good scores confirming Europe’s global leadership in the deployment of solar PV energy. A diversification of the market is taking place with countries adopting appropriate support policies.

The aim of this paper is to provide an overview of the methods of automation and their application areas. Current technologies and their applications in both crystalline and thin-film technology will be the main focus, with detailing of the value chain, starting from the feedstock to the finished product. For ease of discussion, the focus is on the part of the value chain where discrete manufacturing on the substrates takes place: for thin film, the feed-in of substrates into the line, and for crystalline technologies, the focus is on wafer manufacturing.

The European PV committee of EPIA/SEMI released the new PVECI standard that describes a unified IT interface for PV equipment in March 2009. If used properly, it provides the PV industry with a powerful tool for reduction of IT-related issues – especially between the factory planning and the ramp-up phase – and establishes the basis for deploying advanced factory management and control software systems. The first part of this article describes the standard in detail while the second part focuses on the anticipated benefits regarding IT integration and outlines further possibilities of a pervasive Production-IT landscape.

Amorphous silicon is one of the most effective materials in passivating silicon interfaces. At Fraunhofer ISE, highly passivating amorphous silicon coatings were developed by an industrially applicable Plasma-Enhanced Chemical Vapour Deposition (PECVD) process. Thin-film stacks of amorphous silicon and SiOx display excellent passivation quality, indicated by effective charge carrier lifetimes ranging from 900 to 1600µs and resulting surface recombination velocities between 9 and 3cm/s-1. The demonstrated temperature stability opens up new application opportunities also for amorphous silicon films in the industrial production of highly efficient solar cell structures, which will be further discussed in this paper.

Despite the low-cost, high-efficiency, radical form factor promise of many thin-film photovoltaic technologies, scaling these materials to large-volume production has presented a wide array of challenges. Because of the recent polysilicon shortage, an incredible amount of resources have been focused on this goal and many thin-film alternatives are now available. One of the most intriguing of these materials, copper indium gallium diselenide (CIGS), has great potential to reset the thin-film market and make new applications cost effective and viable. CIGS technology is differentiated from competing PV materials by a combination of factors. The manufacturing cost of thin-film cells can be very inexpensive since they require few raw materials and can be made with an efficient, scalable roll-to-roll process. CIGS has been established as the most efficient thin-film technology in converting sunlight into electricity. A flexible substrate will ultimately enable energy and building-integrated applications beyond the capability of rigid, heavier PV products.