OK, so these solar cells are highly weight efficient. But since when do we measure solar cell efficiency by weight? We measure in two ways 1) by areal efficiency, e.g. watts/m2. 2) by overall energy efficiency, ie the light energy vs electrical energy, where this is typically nowadays about 20%

So taking the figures provided in the article, these cells are said to be 100 times less heavy per unit area than conventional cells, but we're also told they generate 18 times more power per kg. In other words, in areal efficiency then this implies that they're actually five times less efficient than conventional solar cells. (The general commercial efficiency is around 20% where a 1 sq metre panel will produce e maximum of 200 watts)

Most roofs are capable of taking standard solar panels, so it's not the weight that's particularly important. It's hard enough to get 4 kw of solar power on most roofs, you'd need a roof five times as large to do this with these lightweight panels.

Now, it may be that this report has inaccurately relayed this technical information, I must say it would be difficult to claim much advance if the panels were literally five times less efficient, but I make this comment so as to put some perspective on the claims. Things like robustness, longevity etc are also issues.