News Article
Mitsubishi Electric develops practical use multi crystalline solar cell
The solar cells will produce an efficiency rate of 18.6%;;
Mitsubishi Electric Corporation announced its achievement of a world record1 photoelectric conversion efficiency rate of 18.6 percent3 in a 150 millimetre square practical use multi-crystalline silicon solar cell, an improvement of 0.6 percent over the company's previous record4.Production volumes of solar, or photovoltaic (PV), systems have been increasing as they have garnered attention as a good source of renewable energy, against the background of increased global environmental awareness. While silicon is an essential component in the wafers used to make solar cells, the supply of silicon has not been able to keep up with demand. This is driving research into the development of thinner wafers that not only use less silicon, but also have improved efficiency and increased electrical output. In a 150 millimetre square practical use multi crystalline silicon solar cell, Mitsubishi Electric has achieved the world's highest conversion efficiency rate of 18.6 percent by adding a low reflectivity surface texture on the multi crystalline silicon wafer, by optimising the p-n junction to increase electric current generation and by developing a process to print electrodes on the surface of the silicon (metallisation) to reduce shade loss of front grid electrodes. This technology contributes to higher efficiency in small installations such as narrow roofs.Main features of the newly developed PV cell are a low reflective honeycomb textured structure, with a view to using the technology in next generation high efficient PV cells. To create highly efficient PV cells, it is necessary to reduce light reflectivity on the surface. While a honeycomb textured structure5 is recognised as suitable for reducing surface reflectivity, it was a challenge to develop a way to apply this technology in production lines. Mitsubishi Electric has developed the world's first1 method6 for fabricating a honeycomb structure on the surface of a 150 millimetre square multi crystalline silicon by combining laser patterning and wet etching. Reduced emitter loss by optimising the n-layer in p-n junction. Power generation also relies on the amount of light that approaches the p-n junction. A shallow, lightly doped emitter (n-layer) increases light gain and improves efficiency of power generation. 25-percent reduced shade loss from front grid electrodes and larger effective electrical output surface area. With modified screens and front metal electrodes, Mitsubishi Electric reduced shading loss of front grid electrodes by 25 percent compared to previous cells.Future Developments:Mitsubishi Electric will begin introducing this multi crystal silicon cell technology into its mass-produced photovoltaic modules by fiscal 2011. Mitsubishi Electric also aims to increase output of solar power generation systems by combining this technology with its PV inverters. The company will promote these PV systems worldwide, thus contributing to environmental preservation and achieving a sustainable society. The company plans to make a presentation of this achievement at "The 23rd European Photovoltaic Conference" in September 2008 in Spain.
