Generally EVA film is used for encapsulation of photovoltaic modules. An alternative to EVA film has been developed from a polyolefin material. Dow Chemical Company’s ENLIGHT™ Polyolefin Encapsulant Films, can not only enhance efficiencies in photovoltaic (PV) module production, but also lead to lower conversion costs. The films can also provide greater module stability and improved electrical performance as compared to traditional encapsulants, such as EVA-based products, improving the reliability and extending the service life of PV modules. The new encapsulant films are suitable for C-Si and thin-film modules. These Polyolefin Encapsulant Films provide a number of benefits that help lower the total system costs of producing and using modules- they reduce cycle times up to 30% and extend lamination temperature windows. The physical properties virtually eliminate bubbles, which leads to fewer rejects. Damage to equipment and modules is also markedly reduced because the process does not produce acetic acid. Based on fully integrated polyolefin technology, these encapsulant films: • Can be formulated to address specific module design needs; • Provide Water Vapor Transmission Rates (WVTR) that can range from 10-20 times lower than EVA materials; • Allow excellent adhesion to glass under various lamination conditions; • Show no creep in use; • Offer a better matched refractive index to glass compared to EVA; and • Are listed with Underwriters Laboratories (UL) as “Recognized Components.” Modules made with these films can retain efficiency levels after more than 10,000 hours of damp heat exposure, whereas Dow testing shows that modules made with EVA typically show a sharp drop off in efficiency levels after more than 2,000 hours in damp heat. In another development, DuPont is developing Kapton colorless polyimide film for use as a flexible superstrate for cadmium telluride (CdTe) thin film photovoltaic (PV) modules. The film was used by Swiss research institute Empa to reach CdTe conversion efficiency of 13.8%. The efficiency is near to that of glass-based photovoltaics panels. Kapton film is flexible and is over 100 times thinner and 200 times lighter than traditional PV glass. It enables solar cell manufacturers to produce products at higher speed and lower cost on roll-to-roll (R2R) deposition equipment. Installation or balance of systems (BOS) and shipping costs can also be cut with the film-based cells, particularly for building integrated photovoltaics (BIPV). Flexible CdTe cells could be rolled up and carried to an install site, rather than lifted with a crane. The Lab has been working on developing and optimizing a low deposition temperature (<450C) process for high-efficiency CdTe solar cells on glass (15.6% efficiency) and polymer film (12.6% efficiency). Empa is currently exploring materials to further these efficiencies in this process. Dow expects to commercialization in 2012. Another development features a breakthrough with the potential to improve the thin film manufacturing process. Thin film solar cells are considered by many to have great potential in that they can be applied to surfaces where standard photovoltaic modules cannot. However, slow and labor intensive manufacture of thin film modules has hampered rapid development in the field. Center for Solar Energy and Hydrogen Research (ZSW), Stuttgart, Germany, has announced findings that may solve these problems making the manufacture of thin film photovoltaic more efficient. The new development deposits CIG cells simultaneously on micrometer thin polymer film, without compromising photovoltaic efficiency. The ZSW laboratory experiments have resulted in a method for, "efficient web coating of thin film solar modules made of copper indium gallium diselenide (CIGS) on plastic film." At the same time, the solar cells maintain efficiency of 10.2%. ZSW claimed this has the potential to, "create a new generation of affordable, flexible photovoltaic modules." The ZSW researchers previously had developed a technique whereby all the production steps were completed in one continuously running system, as per PV Magazine. But in the new development, CIG application processes can be completed at the same time. This will result in first integrating a vacuum-deposited buffer layer and matching the deposition speed of all coating processes. The CIGS coating process used by the research team is cathode sputtering but, the co-evaporation of the CIGS absorber and the deposition of the transparent front contact layer are located elsewhere in the system. While the ZSW research may have reduced the CIGS deposition process to one stage, CIG thin film manufacture remains a multi-stage process. Since the process is carried out in a vacuum chamber, the interfaces will not be contaminated by oxygen or atmospheric moisture. Although whether this is advantageous to the production process is not clear. The timeframe for commercial application of this technology is anticipated between 5-10 years. Another German team has developed a specially coated barrier film for protecting inorganic solar cells. A barrier layer or film is required to shield thin-film solar cell from water vapor and oxygen and to enhance the cell’s lifetime. Dr. Klaus Noller, scientist at the Fraunhofer Institute for Process Engineering and Packaging IVV in Freising, explained the benefits of plastic films. The flexibility and low weight of the material allow for new manufacturing processes that result in reducing the expenses of photovoltaic module production. Thus, printing of solar cells can be done on a plastic film and can be covered with a barrier film. Dr. Sabine Amberg-Schwab, researcher at the Fraunhofer Institute for Silicate Research ISC in Würzburg, has been working with her team for several years to develop a coating material based on ORMOCER polymers. These polymers can be deployed as an efficient barrier against water vapor and oxygen. The resultant barrier lacquer was integrated with another barrier material such as silicon dioxide. Such combination produced excellent results and the barrier effect was better than adding two layers. The ORMOCER-based coating material that can be cured and processed easily. The damp testing has shown that the cured lacquer coating needs to be maintained at 85% humidity and 85°C. Hence, the major challenge for the researchers is to develop a process to apply the barrier layers on the film in a perfect and economical way. This obstacle was overcome with the help of a roll-to-roll process. Under the process, the application of the ORMOCER coating has to be done in a dust-free environment. Organic photovoltaic cells (OPV) are finally becoming competitive with crystalline silicon modules in terms of efficiency, stability and cost. Over the last few years, efficiency of OPVs has gone from 1-2% to about 9%. Recently, a project funded by FlexTech Alliance helped boost efficiency to nearly 12% using high-efficiency donor polymer materials developed by Solarmer Energy Inc. This project builds upon previous designs to synthesize a new active layer material in polymer solar cells that delivers improved properties such as low bandgap, appropriate molecular energy levels, good mobility and excellent processability. Other types of flexible substrates also have the potential to reduce the cost/watt of solar energy and improve lifetime performance of photovoltaics. Manufacturing costs of flexible solar cells may soon be further reduced by means of a high-speed atomic layer deposition (ALD) system under development at Cambridge NanoTech. ALD is an ideal coating technology because of its perfect, conformal, ultra-thin films that are scalable to large-area substrates. FlexTech Alliance awarded a contract to Cambridge NanoTech to develop a system that, when completed, will enable the manufacturing of large-area and flexible substrates for use in organic electronics, solar cells, biomedical devices and displays. Vast improvements made by companies such as Solarmer Energy are approaching the sub-$0.50/Watt level needed to outperform traditional power production on a financial basis and trigger true economies-of-scale in solar manufacturing.