[PVSEC] Honda Unveils CIGS Technology Filled With Surprising Data

Honda has revealed the technical details of its CIGS solar cell module for the first time, which it started selling across Japan in October 2007.
Hearing the data for the first time, some people in the audience were heard expressing their surprise, saying "The variation of conversion efficiency is smaller than that of other manufacturers " and "It is interesting to see the great progress in development since 1997." The technology was announced under the names of Honda Engineering Co Ltd and Honda Soltec Co Ltd.
Honda said it began the research and development in 1997 and achieved an energy conversion efficiency of 18.1% on a 0.5 x 0.5cm substrate basis in 1999. Then the company changed directions to the expansion of substrate size in view of commercialization.
As a result, Honda increased energy conversion efficiency per module to 10.4% on a 10 x 10cm substrate basis in 2002, 11.2% on a 20 x 20cm basis in 2003, 12.7% in 2006 and 13.9% in 2007 on a 73 x 92cm basis.
Honda cited three technical features of its CIGS solar module. They were (1) selenide process, (2) Na coating process and (3) an InS buffer layer.
Selenide process and Na coating process stem from the use of low-alkali glass substrates. When seleniding, a more crystalline CIGS layer is formed because low-alkali glass allows heating at more than 500°C, which is difficult for standard glass.
On the other hand, standard glass becomes more crystalline when the Na contained in the glass spreads. Low-alkali glass, however, does not exhibit this effect and therefore Na must be added. Honda sprays a solution containing Na to low-alkali glass using a spray gun for automobile coating.
As for the buffer layer, Honda used InS to avoid using Cd, although many other solar cell manufacturers use CdS.
Conversion efficiency of a module that Honda is currently mass-producing is 11.1% on average and 11.6% at maximum. Having marked a maximum efficiency of 12.2% at a pilot line, however, Honda is planning to gradually transfer the technology to the mass-production line.