Hanwha’s patent concerned a more efficient solar cell using a double dielectric layer stack that reduced recombination loses by increasing surface passivation. Claim 9 was directed to a solar cell and it recited that there was a silicon substrate, a first dielectric layer comprising aluminium oxide on the surface of the silicon substrate having a thickness less than 50mm and a second dielectric layer on the surface of the first dielectric having various specified characteristics.
The prior art document, a patent application referred to as ‘Isaka’, disclosed a solar cell that had a silicon substrate, a first passivation film and a second passivation film, formed between the substrate and the first film, that included “a silicon oxide film and/or an aluminium oxide film”. Did Isaka disclose the feature of claim 9 of a first dielectric layer of aluminium oxide?
The court accepted that the skilled reader of Isaka would understand that the choice of aluminium oxide was one preference. It would seem therefore that Isaka did disclose the use of aluminium oxide as the intervening film. But this proposition, was not accepted by the court.
The problem was that following the instructions in Isaka would not inevitably result in a functioning solar cell being produced. The difficulty lay in obtaining a functional cell.
The particular design of the solar cell in Isaka meant that it would be difficult to get a working cell using aluminium oxide, even though a layer of this material had been recommended. Further, the particular characteristic of aluminium oxide that led to the difficulty, its negative charge, was not commonly known at the priority date. Isaka neither revealed this difficulty nor how it could be overcome.
Hence whilst Isaka clearly stated that aluminium oxide could be used, the skilled reader following the directions may not have been able to make a solar cell that worked. The feature in question was held not to be disclosed.
The case illustrates the limitations of the “inevitably result” test. Whilst the words of an alleged anticipation may literally disclose a feature, this may not be enough if other information needed to produce a functioning product is missing.
