Fascinating research on the upper limit of light absorption by solar cells. Utilizing nanophotonic technology and thin-film solar cells, the efficiency is given an impressive boost. I keep hammering on the same point, but cost and efficiency in combination are the key to making solar a commercially viable option. Throw in some short-term government subsidies (I know, I know) and we are getting close to that sweet spot.
From the link:
But things have changed since the 1980s, not least because it is now possible to make layers of silicon much thinner than the wavelength of the light they are expected to absorb and to carve intricate patterns in these layers. How does this nanophotonic technology change the effect of light trapping?
Today, Zongfu Yu and buddies at Stanford University in California, tackle this question and say that nanophotonics dramatically changes the game.
That’s basically because light trapping works in a different way on these scales. Instead of total internal reflection, light becomes trapped on the surface of nanolayers, which act like waveguides. This increases the amount of time the photons spend in the material and so also improves the chances of absorption.
Because of the geometry of the layers, some wavelengths are trapped better than others and this gives rise to resonances at certain frequencies.
What Yu and co show is that by designing the layers in a way that traps light effectively, it is possible to beat the old limit by a substantial margin.
Also from the link:
Physicists have long known that thinner solar cells are better in a number of ways: they use less material and so are cheaper to make and the electrons they produce are easier to collect making them potentially more efficient. Now they know that light trapping is more effective in thinner layers too.