This sixteenth edition of Photovoltaics International marks four years of production of the quarterly journal. As always, our focus is on efficiency and quality improvement and cost reduction in manufacturing.
Lifetime guarantees of more than 20 years are a target for the long-term stability of solar modules. An important point for the future of CIGS solar cells is to understand the impact of metastable behaviour on long-term stability. Accelerated ageing under open-circuit conditions leads to a drop in open-circuit voltage (Voc). A decrease in the net doping density is responsible for the drop in Voc and consequently the drop in the photoluminescence (PL). In the initial state the electroluminescence (EL) ideality factor exhibits a value close to unity, as expected from theory. After the dark anneal an increase in the EL ideality factor is observed, and an EL measurement at constant voltage shows a decrease in EL: both these behaviours are due to a pile-up of negative charges at the heterointerface. The application of a positive bias or an illumination during the endurance test leads to an optimization of stability. This paper shows that PL and EL can distinguish between bulk and interface properties and are well suited for the detection of degradation mechanisms.
What does an industry need for sustainable, long-term success? A market, customers and suppliers, and – most certainly – excellent products that can be sold. When looking at various different mature industries there is one thing they all have in common – they have industry-initiated roadmaps! With SEMI’s experience in the semiconductor industry over the last 40 years, the example of the International Technology Roadmap for Semiconductors (ITRS) has proved that pre-competitive industry collaboration among the supply chain and among competitors leads to a reduction in costs, a better time to market and an increased efficiency. Moreover, it helps all players to benefit from jointly solved manufacturing challenges.
Although the different roadmaps for PV vary somewhat from each other, the bottom line always remains the same: exponential growth is predicted over the next 5 –10 years. The latest cell technologies meet the demand for grid parity even in central Europe and PV will therefore continue to be the most popular source of renewable energy. In consequence, the whole PV industry has developed from a niche product towards mass production. Every player along the entire value chain is now faced with the need to stay profitable while meeting the ever-increasing demands of the market. Implementing suitable automation can improve competitiveness and thus pave the way to becoming or remaining successful in this turbulent market.
Recently, PV demand forecasting has seen greater contributions from countries that had previously been lumped together in the rest-of-world (RoW) bucket – a category previously reserved for the collective PV demand from countries or regions outside of major (FiT-stimulated) European PV markets. Research has shown that PV adoption outside Europe will not simply increase overall PV demand levels, but will assist in smoothing out erratic demand cyclicality. At first glance, the increased gigawattage of demand being added from the RoW grouping provides an essential component in driving long-term industry growth scenarios. Non-European PV demand is forecast to increase from approximately 30% to 60% of global PV demand between 2011 and 2016. However, more tangible benefits of having an increased number of countries feeding into the global demand mix extend beyond just the significant ‘growth’ potential this situation offers to the PV supply chain. Of these various benefits, perhaps the one that will provide the greatest level of comfort to the PV supply chain will be a collective ‘smoothing’ effect in quarterly demand swings. This should have a positive effect on factory shipment schedules and hopefully provide an end to some of the boom-and-bust cycles that have negatively impacted the fortunes of the PV supply chain during 2010 and 2011.
Flexible copper-indium-gallium-(di)selenide (CIGS) absorbers offer a wide range of possible applications in rigid as well as flexible and lightweight solar module designs. The main advantage of CIGS in comparison to the well-known flexible module technology based on amorphous silicon is its currently higher efficiency and the promising optimization potential of its efficiency in the future. Because of low cell thicknesses of less than 40µm and the general sensitivity of CIGS to moisture, it is a challenge to develop suitable interconnection and encapsulation technologies that promote long-term reliability of solar modules. Selected aspects of our work in this area will be discussed in this paper.
With current state-of-the-art PV module tests stipulating only a static mechanical load test in accordance with IEC 61215 and IEC 61646 standards, hardly any fatigue stressing is carried out on cells, cell connectors or rigid component parts such as the glass or framing. This paper presents research on dynamic load testing of PV modules and discusses reliability aspects of these essential requirements that must be considered in future standardization work.
Wet chemical process equipment is widely used in industrial solar cell production, and inline etching systems in particular have attracted more and more attention since their introduction 10 years ago. The horizontal wafer transport within these systems has made it possible to think about single-side wafer treatments even for wet chemical process applications. Since its market introduction in 2004, the chemical edge isolation process based on the single-side removal of the parasitic emitter at the rear side of the solar cells has gained an increasing share of the market in comparison to competing technologies that use laser techniques. However, stabilization and control of such a process under mass production conditions remains challenging. The introduction of new high-efficiency cell concepts involving passivated rear sides will increase the importance of single-side wafer treatments, as the final solar cell performance is significantly affected not only by the complete removal of the parasitic emitter but also by an ideally polished surface on the rear side of the wafer.
This paper presents Calyxo’s recent advances in product design that have resulted in independently confirmed peak aperture-area efficiencies of 13.4% for modules and 16.2% for cells. Some insight is given into a suitable product design for achieving the highest reliability possible, even in hot climates such as Australia, with no signs of degradation during the first three years of deployment in the field. These technical advances and the midterm production-cost target of US$0.50/Wp allow a forecast levelized cost of electricity (LCOE) of under US$0.10/KWh, especially in sunny regions of the world.
A typical financial structure for a utility-scale (i.e. larger than a few MW) PV project is the so-called ‘non-recourse project financing’. Experience shows that lenders may occasionally refuse financing because they dislike a technology or even a certain supplier. This past behaviour has created the ‘myth of bankability’ and the perceived necessity of manufacturers to get onto the banks’ ‘bankability lists’. But there is no strictly defined process for doing this, and many of the experienced banks do not even work with such lists for good reason. Moreover, ‘bankability’ is not a feature that a manufacturer or a product can achieve or maintain forever.
