Printed Photovoltaics in Japan

Dr Peter Harrop, Chairman at IDTechEx looks at printed photovoltaics in Japan and Asia.

Photovoltaics (PV) are progressing from the old crystalline and amorphous silicon to thin film technologies that are increasingly printed. There are several types of solar cell involved and they are all needed as the market grows and fragments. For example, transparent versions based on inorganic compounds are valued on the face of a wristwatch or on a window.

Dye Sensitised Solar Cells (DSSC) are already printed reel-to-reel and they are exceptionally efficient in poor light levels and some even work from heat. They combine inorganic and organic compounds. Printed organic photovoltaics on its own is another option. It promises uses involving very low cost and a wide area despite poor efficiency, but lifespans needs to be improved. Thin film cadmium selenide/cadmium telluride versions have already beaten silicon on cost of ownership, but it is proving difficult to print so that volume production can be achieved at an even lower cost.

Japan is different

In the US, the European invention of DSSC is largely ignored, but Japan, like Europe, is energetically pursuing this option.

All is not plain sailing in Japan, however. Thanks to government subsidies, the Japanese used to have more PV installed than any other country, but the subsidies have now largely dried up. In 2007, PV installations plummeted to 165 MW from 287 MW the year before.

It is the more consistent Germans that now have more installed PV than the rest of the world combined. Some in Japan believe that even conventional silicon can achieve grid parity by 2013 and that it therefore does not need much of a fiscal push. Others see strong reasons for supporting the industry, notably development of a variety of types of thin film PV, and Japan can excel at all of these.

CIGS

Many technologies are seen as contributors to this grand vision and already the Research Center for Photovoltaics at the National Institute for Advanced Industrial Science has demonstrated 15.9% efficiency for copper indium gallium diselenide (CIGS) cells on a rigid substrate, and is set for 15% efficiency 30cm² panels by year end. Showa Shell is reportedly near to a major rollout of this technology and Honda Soltec already has its reel-to-reel CIGS PV factory on stream. Honda's next-generation solar cell achieves 50% reduction in the amount of energy consumed during the manufacturing process compared to what is required to produce conventional crystal silicon solar cells. This makes the new solar cell more environmentally-friendly by reducing the amount of carbon dioxide generated even from the production stage.

Other options

Matsushita, Micro-tec, NEC, SEL, Sharp and Tokki are among the other companies developing inorganic compound photovoltaics in Japan, as are many local universities and research institutes. Several are working on DSSC which combine inorganic and organic materials. Konica Minolta, Micro-tec, NEC, Nissan Chemical Industries, SEL, Sharp and other companies are working on purely organic PV backed by many of the leading Japanese universities.

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