[Jedi Master Pikachu]

The thing is supposed to absorb a lot of light (almost all). That's why it could be useful for solar panels.

[beezdotcom]

From the article:

The new material has almost the same refractive index as air

I would assume this means that it is incredibly transparent. Hence, it would make for good LEDs, since nearly ALL of the LED light would escape. It would improve solar cells, since a coating of this material (instead of glass) would allow far more light to reach the cell.