Amorphous silicon thin-film solar cells, to be precise, and an invention you almost certainly used if you were in school in the '80s or '90s, the calculator.

For the first time, the fungibility or the, the scale of solar became, um, very visible to the average consumer.

They could imagine, and they saw images of these huge solar modules on satellites or in field, but knowing that they could also hold it in the palm of their hand and it cost cents.

This idea that there was this scale of solar impact that went to something so, um, minor that they would have access to, I think it opened up, um, a new understanding of the range of impact that solar could have in a way that before that, there was really not that same general understanding in the population.

So here's Danielle Merfeld, global chief technology officer, to explain a little more about tandem technology.

One of the new technologies that we're developing is called tandem technology or tandem solar, and that's taking a conventional single-junction silicon-based solar cell, and on top of it adding a thin film, which can be deposited in a lot of different ways, but this thin film also has some photovoltaic properties, but they...

That, that film or that s- that top cell absorbs a certain portion of the spectrum that's different from the bottom cell.

And so putting those two portions of the spectrum together, you increase your total power, um, that you can make from that solar cell.