The researchers synthesize 21 kg of PbI2 out of a single battery. PbI2 has a density of around 6 g/cm^3. The solar cells have a 500nm coat of PbI2. If I do the

The researchers synthesize 21 kg of PbI2 out of a single battery. PbI2 has a density of around 6 g/cm^3. The solar cells have a 500nm coat of PbI2. If I do the math, then I get 7000 m^2 of solar panels out of it [1], which is 10x more than what they claim. How can this be? In the paper [2], on the bottom of page 4, they give the answer to this discrepancy: "By considering the structure of PSCs (~500 nm-thick PbI2 coating) and the material loss during the spin-coating process (~89.6%), 21.5 kg of PbI2 enables the fabrication of ~709.0 m2 PSCs." This seems ridiculous. If you use 21 kg of material for spin coating, 19 kg don't just vanish into thin air. I would imagine that the material that is flung off can be collected in the bottom (or somewhere else). But maybe that is not possible? If 90% of the material would disappear during spin-coating, then how can the researches claim that they safely recycle lead? They are doing the exact opposite! [1] https://www.google.com/search?q=21+kg+%2F+(6+g%2F(cm^3))%2F(500+nm) https://www.google.com/search?q=21+kg+%2F+(6+g%2F(cm^3))%2F(... [2] http://pubs.rsc.org/en/Content/ArticleLanding/2014/EE/C4EE00965G http://pubs.rsc.org/en/Content/ArticleLanding/2014/EE/C4EE00...