Detail: it's not a "visible lightwave" cell, it captures near infra red and other part of the non visible spectrum, so the usual light energy is not absorbed, it's 95%+ transparent for us, but it yields some voltage. I don't have the figures (I should have looked at); the first company I've seen was Ubiquitous Energy (from a Stanford or MIT lab prof. circa 2013). I've read on some research paper that there are other in the competition.

Maybe the power output is too low.. considering how many zillions of office windows could be converted I assumed they'd be as famous as tesla.