Seems to be 1000x times by weight. >“Pound for pound the new solar cells produce up to 1,000 times more power than conventional photovoltaics. At about one nanometer (billionth of a meter) in thickness, it’s 20 to 50 times thinner than the thinnest solar cell that can be made today,” Grossman adds. “You couldn’t make a solar cell any thinner.” https://cleantechnica.com/2013/06/28/ultra-thin-solar-cells-1000-times-more-powerful-than-conventional-pv-per-pound/