Mitsubishi Electric sets two world records in solar cell conversion efficiency

TOKYO, JAPAN: Mitsubishi Electric Corp. has set two world records for photoelectric conversion efficiency in polycrystalline silicon photovoltaic (PV) cells, achieved by reducing resistive loss in the cells. Photoelectric conversion efficiency is the rate at which sunlight energy is converted into electricity, with higher rates meaning more output.

In response to the growing demand for PV systems that help tackle global warming, the global production of PV cells has reached 5,500 megawatts (MW) in the fiscal year ending March 2009 (FY2009), and is expected to reach 8,000 MW in FY2012.

With the use of crystalline silicon PV cells continuing to increase, PV cell manufacturers are looking for ways to improve the conversion efficiency of these cells to gain more output power from limited surfaces. At the same time, PV cell manufacturers are trying to achieve more output power while reducing the thickness of PV cells, thereby reducing their dependence on silicon and the related risk of sharply fluctuating prices for this material.

One of the world records, which Mitsubishi Electric has now renewed for the third consecutive year, is a 19.3-percent efficiency rating for photoelectric conversion of a practically-sized polycrystalline silicon PV cell of 100 squared centimeters or larger, with the PV cell measuring approximately 15 cm x 15 cm x 200 micrometers. The rating is 0.2 points higher than the company's previous record of 19.1 percent.

The second world record, achieved with the same technologies in an ultra-thin polycrystalline silicon PV cell measuring approximately 15 cm x 15 cm x 100 micrometers, is an efficiency rating of 18.1 percent, a 0.7-point improvement over the company's previous record of 17.4 percent.

The conversion efficiency rates have been confirmed by the National Institute of Advanced Industrial Science and Technology (AIST), in Japan.

Mitsubishi Electric will be developing mass-production technology to deliver these high conversion rates in commercial PV modules. The company also aims to increase the output of its PV systems by combining this technology with PV inverters capable of high-efficiency conversion of DC current to AC. By improving the efficiency of its PV systems, Mitsubishi Electric expects to contribute to environmental preservation as well as sustainable societies.