Photovoltaics International Papers

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.

The principal paths to cost reduction for the photovoltaics industry are increasing the efficiency of solar cells and the power density of modules, together with the reduction of the specific consumption of silicon. Following the slowdown in the ever-increasing growth of the PV market earlier this year, and the reduction in the market cost of polysilicon, wafer producers and most cell producers moved back to the 180µm generation substrates. It may take some time for manufacturers to tackle the technological issues that need to be addressed in order to successfully decrease wafer thickness further. In this article, some of the issues related to the production of thinner and thinner cells are outlined and discussed.

In order to stimulate the economy and create jobs, the bill includes over US$6 billion in loan guarantees for renewable energy projects, solar in particular. Industry representatives have estimated that the bill will create 67,000 jobs in the solar power sector this year and a total of 119,000 jobs over the next two years.

Transparent conducting oxides (TCOs) are a special class of materials that can simultaneously be both optically transparent and electrically conducting and, as such, are a critical component in most thin-film photovoltaics. TCOs are generally based on a limited class of metal oxide semiconductors such In2O3, ZnO and SnO2, which are transparent due to their large band gap energy and can also tolerate very high electronic doping concentrations to yield conductivities of 1000S/cm or higher. However, these thee basic TCOs alone do not meet the TCO performance needs of emerging PV and other applications.

Crystalline silicon solar cell fabrication involves many wet chemical process steps. Like most processes in solar cell manufacturing, many of these wet chemical processes were transferred from the semiconductor industry. In contrast to microchip fabrication with maximum throughputs of 100 wafers/hour, state-of-the-art solar cell equipment relies on several 1000 wafers/hour. Furthermore, specific processes have been developed for the texturisation of the wafer surface. Therefore, there is a need for dedicated methods of characterization of these wet chemical processes. Fraunhofer ISE has developed several analytical methods such as titration, ion chromatography and near infrared (NIR) spectroscopy for the complete analysis of the chemical composition of wet chemical processes baths. These methods were compared considering the inline/online capability, measurement cycle and running costs, with the result that NIR spectroscopy was identified as a complex but very powerful tool for process characterization, as outlined in this paper.

Glass has been playing an ever more important role in photovoltaics, and with the increasing demand for solar modules, the glass industry will be pushed even more to the fore. As a result, the photovoltaics industry is fast becoming a field of business of increasing importance for some of the glass industry’s sectors. Mechanical engineering companies around the world are working to meet the demands of the solar industry, with the tremendous potential of glass, especially in the thin-film sector, at the epicentre of this effort. This paper presents the beneficial properties of glass for use in the photovoltaics industry, and the material’s potential for future applications.