Mitsubishi Electric develops highest efficiency multicrystalline Si solar cell
Mitsubishi Electric develops practical use Multi-crystalline Silicon Solar Cell with world’s highest conversion efficiency of 18%
Tokyo, May 31, 2007
Source: Mitsubishi Electric /press release
http://global.mitsubishielectric.com/bu/solar/products/pdf/PVe_0531.pdf
Mitsubishi Electric Corporation (President and CEO: Setsuhiro Shimomura)
announced today its achievement of a world record (As of May 31, 2007) photoelectric conversion efficiency rate of 18.0% in a 150mm square practical use multi-crystalline silicon solar cell (Results from evaluation by the National Institute of Advanced Industrial Science And Technology (AIST), a public verification agency), an improvement of 1.2% over our previous models. We plan to present our technology at the Fukuoka 17th International
Photovoltaic Science and Engineering Conference in December 2007.
Background and intent of development
Due to increased global awareness of environmental preservation, photovoltaic production volume has been increasing as PV systems have garnered attention as a source of renewable energy. Silicon is an essential component in the wafers used to make solar cells, however the supply of silicon has not been able keep up with demand. Therefore, research continues in making thinner wafers that use less silicon and improving efficiency while also increasing electrical output.
We achieved the world’s highest conversion efficiency rate of 18.0% by adding a low reflectivity surface texture on the multi-crystalline silicon as well as developing a process to print electrodes on the surface of the silicon (metallization) and reducing shade loss of front grid electrodes. In the same
surface area as previous products, we have achieved a 7% greater electric output, making it suitable for even smaller installations such as narrow roofs.
Main features of cell
1. Increased light absorption using a unique Reactive Ion Etching (RIE) method Using a nano-sized mask material, the RIE method uses highly reactive ions generated by RF plasma, letting ions precisely etch the target materials. This decreases reflectivity from the texturized surface of the multi-crystalline silicon, increasing the amount of absorbed light (
Based in part on the result of the NEDO commissioned project for R&D of innovative next generation photovoltaic system technology)
2. Suppresses reduced electrical performance in crystalline.
New metal electrode material reduces metallization time by approximately half that of previous models, and sustains electrical performance of crystalline.
3. Expanded effective electrical output surface area
Using modified screens and front metal electrodes we reduced shading loss of front grid electrodes by 40% compared with our conventional cells
Future developments
We will begin introducing this technology into our mass produced photovoltaic modules after the end of 2007. Pairing this with our power module, which has the industry’s highest energy conversion efficiency, will increase output of solar power systems. Mitsubishi Electric is committed to global environmental preservation and sustainable society through the spread of photovoltaic systems.