PVI Issue

Photovoltaics International Volume 3

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The third edition of Photovoltaics International was published in February 2009. In Thin films we offer Heliovolt enabling rapid printing of microscale CIGS films, and Q-Cells presents requirements for improving diffusion techniques for higher efficiency solar cells in Cell Processing. In Market Watch, we discuss how the USA Stimulus Bill will benefit you.

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In this issue...

PVI Paper
Market Watch, Photovoltaics International Papers
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.
PVI Paper
Market Watch, Photovoltaics International Papers
In the few years since the PV cell and module manufacturing industry first hit the radar, the identities of the winners and losers in the race to supply equipment have started to emerge. While some companies can genuinely claim to have been involved in the solar industry for some time, the majority are relatively new on the scene. This is hardly surprising, as the explosive growth in demand spurred any company with matching competences into action. In fact, over 300 equipment companies have been attracted to the industry since 2003 by the prospect of a share in a market valued at $4.4 billion in 2008. For the first time, a detailed analysis of the PV equipment suppliers has been compiled by VLSI Research. The Top 10 in this list are presented here and discussed in relation to their achievements in the industry and their outlook for 2009 and beyond.
PVI Paper
Cell Processing, Photovoltaics International Papers
In any solar cell process, the metallization step is critical as it often sets conditions and limitations for the other process steps. The main metallization technique used today in Si solar cell production is screen-printing of metallic pastes, namely Ag pastes for the front side, Al pastes for most of the rear side, and Ag or Ag-Al pastes for the solder pads at the rear. While these techniques are clearly robust and convenient, they have limitations. Therefore alternatives are being investigated. A technique that is presently finding its way into production is two-step metallization with Ag plating. Another more radical approach is to avoid printing altogether, instead using some kind of ablation followed by plating. For the rear, the full Al-BSF is being replaced by dielectric passivation and local Al-alloyed contacts. Back-contacted cells are increasingly being introduced in production, and they pose very specific challenges to metallization. For the sustainability of Si photovoltaics, it is crucial that the future metallization solutions only make use of abundantly available and non-toxic materials.
PVI Paper
Photovoltaics International Papers, Power Generation
The U.S. residential solar market is poised for growth. For solar companies seeking to capitalize on the growth potential of this market, the keys to success will be sales volume and operating efficiency. Solar employee purchase programs (solar EPPs), which have been initiated by companies as diverse as SunPower, REC Solar, and SolarCity, represent a new and potentially important channel for increasing sales and improving sales efficiency. Driving these programs are increasing corporate sustainability initiatives and growth in voluntary employee benefit offerings, especially employee purchase programs and green benefits. This article provides an introduction to solar employee purchase programs, analysis of the business ecosystem, and discussion of an example program. It is based on the industry’s first report to identify and analyze this emerging trend, which was published by AltaTerra Research in November 2008 [1].
PVI Paper
Market Watch, Photovoltaics International Papers
News of credit crunch woes filtering down the lines over the past few months has instilled a sense of frugality in all industry sectors. While the credit crisis has indeed affected the PV industry, German banks, investors and creditors have claimed that the financing of small PV systems in the private sector seems not to be endangered. Downstream players are still optimistic, but the upstream sector is anticipating severe damage as a result of the economic situation. An interactive workshop-style discussion, hosted by the German market researcher EuPD Research and its consulting division 360Consult, invited top-level executives to contribute their experiences of the current financial situation, as discussed in this paper.
PVI Paper
Photovoltaics International Papers, PV Modules
The rapid expansion of high volume manufacturing to meet growing demand in recent years has highlighted the development of increasingly higher throughput machines, especially in the critical bottleneck process of module assembly, specifically characterised by tabbing and stringing steps. Significant productivity improvements have come about with the development of integrated, highly-automated tabber and stringers from a range of equipment vendors. However, module assembly remains the most expensive step in conventional c-Si cell production. Equipment suppliers are also challenged to meet the evolving demands of processing thinner wafers and to address overall production cost reduction strategies while meeting yield/throughput goals that are seen as a significant enabler of reducing the cost per watt.
PVI Paper
Photovoltaics International Papers, Thin Film
Laser-based tools have become increasingly visible within R&D labs, pilot production lines, and as the preferred technology used by many turnkey suppliers. As equipment types however, relatively little is known about the differences in the laser-based tools used for solar applications within each of the c-Si and thin-film segments. This paper explains the key components of a laser-based tool, and how they are adapting to meet the demands from next-generation production line equipment required by the solar industry.
PVI Paper
Materials, Photovoltaics International Papers
Materials innovation in solar photovoltaic manufacturing has long played a key role in efforts to raise cell and module conversion efficiencies, improve overall device performance and reliability, and lower the overall cost per manufactured watt. Research and development in areas such as ultrathin-silicon wafering and replacement films for thin-film PV transparent conductive oxides often garner much of the industry’s attention. But a wide range of emerging technologies could provide crystalline-silicon and thin-film cell and module manufacturers the kinds of materials solutions that will accelerate their attempts to reach competitive levelized cost of energy metrics and ultimately attain their goal of achieving grid parity with conventional energy sources – as well as open up lucrative market opportunities for the materials suppliers.
PVI Paper
Fab & Facilities, Photovoltaics International Papers
Owing to the huge demand for photovoltaic products, the market is still very attractive for investments in production facilities. Nevertheless, the increasing number of competing photovoltaic manufacturers and the decrease in governmental subsidies require substantial and continuous cost reductions. Whilst existing facilities can save costs by enhancing cell efficiency, optimizing production processes or reducing material costs and other resources, for new manufacturing sites there is a great potential in making efficient use of economies of scale. This also holds true - to some extent – for expanding existing fabs. This paper presents the logistics behind and the benefits of implementing economy of scale in a PV manufacturing facility.
PVI Paper
Fab & Facilities, Photovoltaics International Papers
The PV industry has seen some incredible growth in the last five to eight years. This growth is essential in order to fulfill the challenging targets this industry has set itself to ensure it becomes an economical viable alternative energy source. A negative result of this growth, however, is the inefficient supply chain, where there is a lack of balance between demand and supply. The industry is going from one bottleneck to another. What is the impact of such inefficiencies on the supplier/manufacturer relationship? In this article, we collect information from short interviews of a number of fab managers in the wafer, cell and module domain, and try to answer this question.
PVI Paper
Photovoltaics International Papers, Power Generation
Electricity has been around for a long time and no doubt will be for the foreseeable future, but it is quickly changing its nature. Owing to evolutions in power electronics, sustainable electricity generation and consumption came to the fore and now it is nigh on impossible for photovoltaics to operate without this technology. This holds true for efficient consumption such as plug-in electric and hybrid vehicles or compact efficient lighting. Power electronics need to be taken into account in relation to grids, for example in novel voltage-source HVDC connections. Photovoltaic energy conversion requires power electronics in order to adapt the floating DC-output to a fixed DC-level and typically further to a grid-compatible AC electricity. These converter (mainly inverter) technologies have evolved considerably over the past few years, in much the same way as has PV cell technology, but in a much less apparent fashion. It is, however, expected and required that the technologies will evolve even further to meet the demands of the future market and the electricity grid to which they will be connected. This article intends to give an overview of the challenges ahead for power electronics in photovoltaic energy conversion.
PVI Paper
Photovoltaics International Papers, PV Modules
A total of 2MWp of PV modules were sold on pvXchange’s spot market platform in December 2008. This corresponds to a sharp decrease of 60% when compared to the figures seen in the previous month (5.6MWp). Low trade volumes throughout the years are common on pvXchange; this year, bad weather conditions prevented many new installations, as did the current economic climate that saw many buyers waiting for further price decreases. The closing of long-term contracts has been postponed by many PV companies that are concerned that they will not find customers given the current circumstances. Again, First Solar’s CdTe thin-film modules were the most traded technology item on the pvXchange platform for the month of December.
PVI Paper
Photovoltaics International Papers, PV Modules
Photovoltaic modules and components, due to the nature of their employment, must be designed to withstand the most diverse of environments. The large spectrum of climatic conditions and mechanical stresses that these components must weather merit the application of some standards by which they can be tested for durability, reliability and safety. TÜV Rheinland operates several ISO 17025-accredited laboratories worldwide for type approval testing of flat plate as well as concentrating PV modules, PV components and solar thermal systems. Test data, collected over the past 20 years, shows that there is still a rather high failure rate when it comes to testing of PV modules, and also that there are different failure mechanisms for crystalline and thin-film PV modules. This paper presents data from these tests and draws some conclusions regarding the need for future standards development.
PVI Paper
Photovoltaics International Papers, Power Generation
The past year was characterised by MW-range solar power plants and it was also a year with the highest market growth related to large-scale photovoltaic systems ever. Not only in Spain, where progress does not need to be commented upon at all, but also in some other countries where the cumulative installed power increased significantly. In the European Union progress was observed in among other countries Italy, Czech Republic and France; the German market however decreased slightly but in terms of capacity of installed power output Germany was, despite the market explosion in Spain, almost the same as in year 2007.
PVI Paper
Fab & Facilities, Photovoltaics International Papers
This review is based on primary research of global solar cell and thin-film manufacturing companies that are either currently manufacturing, expanding manufacturing, building facilities for manufacturing or progressing towards establishment of manufacturing facilities.
PVI Paper
Cell Processing, Photovoltaics International Papers
Formation of the pn-junction for charge carrier separation is one of the key processes of a modern high-volume solar cell production. In silicon wafer-based solar cell technology this is achieved by diffusion of phosphorus atoms in boron pre-doped wafers forming a sub-micron shallow n-type emitter in a 200µm-thick p-type base. In this contribution we discuss both the characteristics of emitter doping profiles and the diffusion process itself as required for optimal solar cell conversion efficiencies. In addition we give an overview on state-of-the-art industrial diffusion technologies and conclude with a brief outlook on their evolution.
PVI Paper
Photovoltaics International Papers, Thin Film
In recent years, a new generation of solar electric products has emerged from the lab into the global market: thin-film technologies that employ approximately 1% of the active, expensive photovoltaic material used by standard crystalline-silicon cells. Through a combination of cost advantages and new product applications, CdTe, a-Si and CIGS thin-film PV have the potential to foster a paradigm shift toward distributed electricity generation at cost parity with other forms of energy. But until recently, the photoactive compound has not had a reliable, rapid manufacturing process that could scale effectively to multi-megawatt-scale volume production and provide significant amounts of electricity at the point of use. This article describes a novel process, known as field-assisted simultaneous synthesis and transfer (FASST) printing, a manufacturing approach that enables the rapid printing of microscale CIGS films with p- and n-type nanodomains that are critical for achieving the highest efficiencies possible.
PVI Paper
Materials, Photovoltaics International Papers
Invented in their high efficiency version in the early 1990s, dye-sensitised solar cells (DSCs) entered the global market in 2007 with the first commercial modules based on this versatile, hybrid (organic-inorganic) technology. The 6-7% efficiency of the first modules is a result of their good performance in diffuse light conditions, allowing for the production of electricity both under cloudy conditions and indoors. These low-cost solar cells are manufactured by highly productive roll-to-roll printing methods over rigid or flexible substrates affording modules coloured in widely different tones. These attributes render DSC a photovoltaic technology particularly well suited for BIPV applications and for electrification in developing countries, as discussed in this paper.
PVI Paper
Materials, Photovoltaics International Papers
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.
PVI Paper
Cell Processing, Photovoltaics International Papers
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.
PVI Paper
Photovoltaics International Papers, Thin Film
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.

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