EE Times -Plastic chips tap IR, solar power Potential 30% (?) effeciency

EE Times -Plastic chips tap IR, solar power: "Nanoparticles enhance a material's quantum-mechanical properties because their electrons are confined to a volume smaller than the electron's wavelength.
'In our materials the wavelength of an electron is about 20 nanometers,' said Sargent. 'But our nanoparticles-the quantum dots that we used-ranged from 2 to 6 nm in diameter. So we were very very strongly squeezing the electrons.
'The size of the nanoparticles determines the wavelength to which your device will be sensitive,' he continued. 'By making [semiconducting] particles that are only a few nanometers in size, we squeeze electrons down so far that their wavelength properties can no longer be ignored [in our calculations]-it becomes a quantum-mechanical phenomenon, a so-called quantum dot.'
Sargent chose the 2- to 6-nm range of nanoparticle sizes in order to cover a nearly continuous band of wavelengths starting in the infrared and extending into the visible. However, he said, for the current demonstration he was just trying to achieve the 'world's first,' not the world's most efficient. Next, his group has to prove that its design can actually attain the kind of efficiency that would make it competitive with current silicon cells. The current 1-nm surface coating is, Sargent said, 'too thick-we need to make it easier for the electrons to escape from the nanoparticles by making the coating thinner.'
Sargent estimated the level of improvement he would consider high enough to make a difference in practical applications. Today, he said, plastic photovoltaic cells from other sources operate at about 6 percent efficiency. Sargent claimed that his design could have the potential to operate at upward of 30 percent efficiency, enabling it to compete with silicon cells.
'If we can improve efficiency by one "