solar funnel

[jerryyu]

http://web.mit.edu/newsoffice/2010/solar-antenna-0913.html

 

 

"The antenna consists of a fibrous rope about 10 micrometers (millionths of a meter) long and four micrometers thick, containing about 30 million carbon nanotubes. Strano’s team built, for the first time, a fiber made of two layers of nanotubes with different electrical properties — specifically, different bandgaps.

In any material, electrons can exist at different energy levels. When a photon strikes the surface, it excites an electron to a higher energy level, which is specific to the material. The interaction between the energized electron and the hole it leaves behind is called an exciton, and the difference in energy levels between the hole and the electron is known as the bandgap.

The inner layer of the antenna contains nanotubes with a small bandgap, and nanotubes in the outer layer have a higher bandgap. That’s important because excitons like to flow from high to low energy. In this case, that means the excitons in the outer layer flow to the inner layer, where they can exist in a lower (but still excited) energy state."

 

I am not sure if i got this correctly...so the photons excite the electrons in the nanotube to a higher energy level and since the inner nanotube has a smaller bandgap, the electrons from the outer layer flows to the inner layer? So basically they are extracting electrons from nanotube???

 

 

" the antenna would concentrate photons before the photovoltaic cell converts them to an electrical current. This could be done by constructing the antenna around a core of semiconducting material.

The interface between the semiconductor and the nanotubes would separate the electron from the hole, with electrons being collected at one electrode touching the inner semiconductor, and holes collected at an electrode touching the nanotubes. This system would then generate electric current. The efficiency of such a solar cell would depend on the materials used for the electrode, according to the researchers."

 

This may be my lack of knowledge, but how would the interface between the semiconductor and nanotubes separate the electrons from the hole ?

and after reading this a several times, i still don't understand how "this system" would generate electric current