Kyocera recently announced that it is supplying solar modules for Toyota’s new solar ventilation system, an optional feature on the new Prius introduced in Japan last month.

The modules will be made using the company’s Reactive Ion Etching (RIE) technology, which creates microscopic ridges on the surface of the solar cell using plasma and reductive gases.  According to Kyocera’s press release, the ridges enhance output and conversion efficiency by facilitating better absorption of sunlight. 

The process also yields a “high level of aesthetic quality” and “stylish appearance” by providing a uniform dark navy blue color.

This RIE process is covered by Kyocera’s U.S. Patent No. 7,128,975 (‘975 patent), entitled “Multicrystalline silicon substrate and process for roughening surface thereof.”  The ‘975 patent is directed to a multicrystalline silicon substrate and a process for roughening the substrate’s surface using an alkaline aqueous solution etching step and a dry etching step.

According to the ‘975 patent, this process overcomes the challenge of forming uniform textures in the irregular crystal orientation of multicrystalline substrates and reduces reflectance:

By this method, fine textures can be uniformly formed independent of the irregular orientation of the crystals of multicrystalline silicon. In particular, reflectance can be more effectively reduced in solar cells using multicrystalline silicon.

The ‘975 patent describes a silicon substrate (1) formed by the patented RIE process as having textures (2), or fine textures (22).  According to the ‘975 patent, the ratio of line a (connecting individual peaks of the fine textures (22)) and line b (connecting the two end points 23 and 24) is less than 1.1, which indicates that the heights of the peaks of the fine textures (22) are even.

 

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