The world's biggest exhibition in photovoltaics was held in parallel to the 22nd European Photovoltaic Solar Energy Conference in Milan, Italy, from 3rd to 7th September. It was an impressive event with overall around 500 exhibitors, 3000 scientists, industry representatives and politicians from 83 countries. The total show space was 30,000 sqm, and as in the previous year, German companies held the largest part of it with 42%, followed by Italy with 13%. Germany is the leader in photovoltaics: Although other countries have for sure more sunny days and could use solar energy more easily, in Germany there is a broad platform of R&D institutes, small start-ups and large companies. The focus is on highly efficient technologies, based on the excellent R&D environment, a wide acceptance of the need to use more renewable energies in the future, and a good support by politicians. The largest independent solar cell manufacturing Q-Cells is a German company. Only Sharp in Japan is larger with respect to produced MW per year.
All main aspects of recent developments in photovoltaics were covered in the Milan conference and show - raw materials as well as application in private households, thin film technologies and sophisticated tracking systems.
Major political decisions are about to further increase both the awareness and the broad use of photovoltaics in Europe. In Italy, beginning this year, every new house has to use solar energy - thus creating a huge market for all kinds of technologies, photovoltaic as well as solar-thermal. On the other hand, in the US there is still no regulation about feed-in taxes, making the investment in solar plants way more difficult than in Europe, mainly in Spain and Italy.
Printing is well established in the manufacturing process of bulk silicon solar cells: The fingers for collecting the power produced in the semiconductor are normally screen printed. Special requirements discriminate this process from screen printing as used in graphic arts, mainly the desired high aspect ratios and the consistency in an industrial process. Screen making companies, material and equipment suppliers developed sophisticated solutions to fulfil the demands of this industry.
While bulk silicon, a-Si as well as the new micromorph versions, is still by far the most used material, new technologies come along, namely thin film approaches. They include a-Si on glass or flexible substrates, applied using vacuum processes, and the new material systems like CdTe, CIG, and CIGS. However, printing technologies are at the very beginning of development here. Reasons are the sensitive materials and the very thin layers required in most cases. The potential of those technologies could be assessed by a fact like this: Q-Cells is investing 400 million Euro in R&D this year, half of it for improving their silicon technology, the other 200 million planned for a-Si on flexible substrate and post-silicon technologies. First companies are about to offer flexible solar cells for real use in real products, like the young company Odersun in Frankfurt/ Oder, Germany. Together with a Berlin manufacturer, they developed a bag serving as a "mobile plug", providing energy anytime. The core technology used in this case is called CISCut (Copper-Indium-diSelenide on copper tape) and according to their claims it is the world's fastest reel-to-reel process.
For further information also read Printed and Thin Film Photovoltaics and Batteries or attend Printed Electronics USA.