Transparent solar cell? Can't see it myself

News from the Far East: Japan's National Institute of Materials Science (NIMS) has built a prototype boron nitride solar cell. Boron nitride (BN) is one of that interesting class of materials that can be both a semiconductor and transparent -- like the tin compounds which make the see-through transistors in LCDs. BN is particularly fascinating because it has a wide band-gap, an aspect of the way its electrons are configured that makes it theoretically good at high energy photonics - ultraviolet lasers, for example, or solar cells.

Trouble is, it's hard to add in the extra impurities that turn this interesting prospect into an actual semiconductor - a process known as doping. Getting the right amount of dopants to sit in the right place in the crystal lattice is not something with which BN likes to co-operate.

NIMS has come up with a way of bonding slicon to BN so that the junction has all the right aspects - and one of the first examples of this is a transparent solar cell. That may seem like a rather odd thing to want to do -- after all, if your solar cell lets all the light through, how can it turn any of it into electricty? Two key observations: first, you only have to let most of the light through to be usefully transparent - and since the BN prototype cell is only 2 percent efficient at conversion, it's clearly, er, clear. The other is that homo sapiens uses an awful lot of transparent materials in buildings and vehicles, so if your windows start to generate power that has great potential. So to speak.

Go and read the original story for more details - microcones! Laser plasmas! Homodiodes! Chips in space! - and prepare for a world where it's far easier to see through claims of effective alternative power.