Mitsubishi Electric To Develop Practical-Use Multi-Crystalline Silicon Solar Cell; Expand PV Cell/Module Production Capacity To 500MW By 2012

March 20, 2008 by Jeff Shepard

Mitsubishi Electric Corp. announced what it claims is a world record photoelectric conversion efficiency rate of 18.6% in a 150mm² practical use multi-crystalline silicon solar cell, an improvement of 0.6% over the company’s previous record.

In a 150mm² practical-use multi-crystalline silicon solar cell, Mitsubishi Electric has achieved the conversion efficiency rate of 18.6% by adding a low reflectivity surface texture on the multi-crystalline silicon wafer, by optimizing the p-n junction to increase electric current generation and by developing a process to print electrodes on the surface of the silicon (metallization) to reduce shade loss of front grid electrodes. This technology is said to contribute to higher efficiency in small installations such as narrow roofs.

Among the 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. Mitsubishi Electric has developed a method for fabricating a honeycomb structure on the surface of a 150mm² multi-crystalline silicon by combining laser patterning and wet etching. 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. With modified screens and front metal electrodes, Mitsubishi Electric claims that it has reduced shading loss of front grid electrodes by 25% compared to previous cells.

Mitsubishi Electric will begin introducing this multi-crystal silicon cell technology into its mass-produced photovoltaic modules by fiscal 2011. The company also aims to increase output of solar power generation systems by combining this technology with its PV inverters, which are said to have the industry’s highest energy conversion efficiency rate.

The company also announced that it will invest a total of some 7 billion yen to expand annual production capacity of PV cells, at its Nakatsugawa Works Iida Factory (Nagano Prefecture), and modules, at its Nakatsugawa Works Kyoto Factory (Kyoto Prefecture), in response to a sharp increase in demand for solar power generation systems. This investment will expand Mitsubishi Electric’s annual PV production capacity from 150MW to 220MW in October 2008. Looking to the future, the company aims to establish a production system with an annual capacity of 500MW by fiscal 2013.