Silicon-based thin-film solar cells have the characteristics of abundant raw materials, non-toxic, non-polluting, low energy consumption, light weight, high conversion rate and low cost, which represent the development trend of the solar energy industry. The new technology is to use radio frequency plasma enhanced chemical vapor deposition technology to prepare amorphous silicon top cells, and high frequency plasma enhanced chemical vapor deposition technology to prepare microcrystalline silicon bottom cells.
Silicon-based thin-film solar cells use much less silicon than conventional solar cells, resulting in lower production costs and lower module prices. However, converting sunlight into electricity is not as efficient as conventional polycrystalline silicon cells.
Thin-film solar modules use very thin silicon coatings or other non-silicon alternatives. Thin-film fabrication involves depositing extremely thin layers of photosensitive materials on glass, metal, or plastic. While most of the common materials used today are amorphous silicon, the latest technologies use non-silicon based materials such as cadmium sulfide.
Currently, materials used in thin-film photovoltaic modules, such as amorphous silicon (a-Si), fragmentation pot (CdTe), copper selenide (CIGS), have attracted great attention and are growing at high rates. This is related to the shortage of silicon and the high production cost of crystalline silicon cells. Thin-film technology helps to reduce manufacturing costs, has the advantage of good versatility, and has competed with conventional crystalline silicon technology in the past few years. However, thin-film PV modules are typically much less efficient than crystalline silicon modules, with conversion efficiencies ranging from 7% to 10%, compared to an average of 15% for crystalline silicon.
As the world’s first manufacturer to provide Turn-Key services for thin-film solar modules, Oer1ikon’s thin-film solar module technical solutions use amorphous silicon and microcrystalline silicon laminated thin-film technologies, including conductive glass (TOC) fabrication, PECVD deposition ( key process steps in the manufacture of thin-film batteries such as plasma chemical vapor deposition) and laser cutting. Thin-film batteries have a history of more than 30 years. Due to the limitation of conversion efficiency, thin-film batteries have not been mass-produced in the past to open up the market. In the past, the conversion efficiency of double-junction amorphous silicon thin-film solar cells was only about 5%, and the packaging technology was also problematic, so the cost advantage of thin-film cells could not be manifested. At present, the industry has gradually entered the stage of mass production of thin-film solar cells. In 2002, Qer1ikon began to fully invest in the project of amorphous and microcrystalline. Using this process, the conversion efficiency after initial attenuation is expected to reach more than 10%. At present, it can guarantee customers to achieve 9.3% conversion efficiency. Through equipment upgrade, the process can be upgraded from amorphous process to non-product plus microcrystalline process. The future bottlenecks of thin-film solar cells are: first, how to improve the conversion efficiency; second, how to improve the manufacturing efficiency of the factory, reducing the time of tack time is very important, that is, shortening the time to manufacture each module; third, to form a scale effect, through Overall control for cost-effectiveness.
Ascent Solar Technology, a developer of flexible thin-film solar photovoltaic modules located in Colorado, USA, announced on December 5, 2008 that the efficiency of its flexible copper selenide steel combined with integrated integrated modules is greater than 9.5%. The National Renewable Energy Laboratory of the U.S. Department of Energy determined that the measured photoelectric conversion efficiency of the module reached 9.64%. The modules tested by NREL were produced by Ascent Solar Technologies on a 1.5MW mid-scale production line, which is said to be an important advance. Many people doubt whether plastic-based thin-film CIGS solar module technology is feasible. Now, Ascent Solar Technologies has not only done just that, but this fully integrated monolithic prototype module has been demonstrated by NREI to be close to 10% efficient. This represents a major advance towards high-performance, inexpensive thin-film solar photovoltaic modules.
Manufacturers of photovoltaic power generation equipment used half of the world’s silicon material in 2005 and are competing with semiconductor and microelectronics companies. In terms of raw materials, about 95% of the world’s photovoltaic power generation uses silicon-based components. But it is believed that this situation will soon change. The use of silicon materials is expected to grow, costs will fall, and the world has begun to use non-polysilicon-based thin-film technology, the second generation of solar photovoltaic technology.
Photovoltaic power generation company located in Hills, Michigan – American Solar Ovenic operates a device in Hills, Michigan, and photovoltaic cells based on thin-film amorphous silicon technology generate about 25MW per year. This technology has two cost advantages, one is raw materials It is silane gas instead of polysilicon which is in short supply, and its raw material cost is much lower than that of polysilicon, and it will not be affected by the shortage of polysilicon; secondly, this type of battery can be made into flexible stainless steel substrate by rolling process, which further reduces the cost . The material converts sunlight into electricity with an efficiency of no more than 15% to 20%, which is inferior to polysilicon-based cells, but it can generate electricity without direct sunlight. For this reason, more power can be generated over a long period of time so that the amount of power generated is the same.
Konarka Corporation of the United States announced a new flexible transparent solar panel invention in May 2009, which can be installed on glass or other transparent materials. This invention can apply solar cells to ordinary buildings, including glass outside Such solar cells can be used on walls and windows. The company’s transparent solar cells are assembled on ordinary glass panels and are available in a variety of colors. These include red, blue and green. This solar panel is based on organic photovoltaic technology, but the conversion efficiency is not as good as that of ordinary silicon panels. The company’s current product energy conversion efficiency is 6%, while the conversion efficiency of ordinary silicon solar panels can reach more than 20%.
A start-up company in the United States has developed a technology to make large rollable solar panels. This tape-and-reel fabrication technique forms thin-film amorphous silicon solar cells on stainless steel sheets. Each solar module is approximately 1m wide and 5.5m long. In contrast to the bulky and rigid image of traditional silicon solar panels, these lightweight, rollable panels are easily integrated into building roofs and façades, and can also be used on vehicle exteriors. What makes the solar panel more attractive than conventional panels is that it can be embedded more easily into irregularly designed roofs. However, the disadvantage is that the efficiency is very low. To improve its efficiency, the company built a triple-structured cell made of 3 different materials (amorphous silicon, amorphous silicon storage, and nanocrystalline silicon), each tuned to capture energy from a different solar spectrum . Although the efficiency of some crystalline silicon modules on the market can reach more than 20%, while the efficiency of rollable photovoltaic modules is only about 8%, its advantage lies in the high-capacity tape-and-reel technology. The tape-and-reel process can reduce costs and expand the scope of application. As of May 2009, the company has received $40 million in investment, and in December 2008 the state of Ohio gave the company a $7 million loan to expedite the construction of a 25MW coiled solar module production line. The company is expected to officially launch its products to the market in 2010.
American Bio Solar announced on July 23, 2009 that it officially launched a new type of back sheet Bio Back sheet-A for thin film solar cells to the thin film solar cell market, which is characterized by a complete moisture barrier. In addition, its new Bio Back sheet-C product, designed to be applied to conventional CS i PV modules, will be commercialized in the second half of the year. Bio Solar believes that the fastest growing segment of the photovoltaic market is thin-film photovoltaics, especially CIGS and CdTe thin-film photovoltaic panels, but the required backsheet has the challenge of having a water vapor transmission rate close to zero. Bio Solar has solved this challenge and successfully developed Bio Back sheet-A product, which is a green module product with absolute moisture barrier properties, three-layer laminated film with 100% recyclable aluminum flute as the middle The core part, composed of bio-based polymer films on both sides, is a unique product in the solar industry. Bio Back sheet-A back sheet product application has achieved great success.
The thin-film photovoltaic sector is not only a fast-growing market, but also benefits greatly from its development. EPIA expects that with increased scale, improved conversion efficiency and the adoption of new production technologies, thin-film module manufacturing costs are expected to drop below 1 EUR/W p in the near future. It is expected that in the next few years, the photoelectric conversion efficiency of thin-film photovoltaics will increase from the current 6% to 12% to 10% to 15%. In a longer period of time, the potential photoelectric conversion efficiency is expected to exceed 20%. Additionally, in addition to the development of new polymers and other types of organic, dye-sensitized solar cells, potential material development includes the development of various technologies (a-Si, a-Si/μc-Si, CIGS and CdTe) optimization.