Mitsubishi record solar efficiency claim - accurate?

Mitsubishi Electric today claimed the world record for conversion efficiency of a 150mm square polysilicon solar cell, seemingly unaware of higher claims made by rival Kyocera seven months ago.

Mitsubishi says its new 18.0% efficiency in a multi-crystalline silicon solar cell is an improvement of 1.2% over its previous models, translating into 7% greater electric output from modules of the same footprint.

Testing was apparently verified by the National Institute of Advanced Industrial Science And Technology (AIST), a public verification agency.

Mitsubishi adding a low reflectivity surface texture on the multi-crystalline silicon as well as developed a process to print electrodes on the surface of the silicon (metallization) and reducing shade loss of front grid electrodes, much like SunPower and others have done.

A new Reactive Ion Etching (RIE) method, using a nano-sized mask material, uses reactive ions generated by RF plasma to precisely etch the target materials. This decreases reflectivity from the texturized surface of the multi-crystalline silicon, increasing the amount of absorbed light, the company said.

In October of last year, Kyocera announced it achieved an efficiency improvement in its polycrystalline solar cells, taking them to 18.5%, by—like SunPower and Mitsubishi—moving the front contacts to the back of the cell (for details, see the Cleantech Group's Solar cell manufacturers duke it out.)

Mitsubishi plans to present its breakthroughs at the Fukuoka 17th International Photovoltaic Science and Engineering Conference in December.

The new techniques are to make their way onto Mitsubishi's production lines next year.

Kyocera, meanwhile, today announced construction has commenced on a second manufacturing facility in Tijuana, Mexico for solar photovoltaic modules, next to its first plant.

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