Quantum-dot solar cells have great potential for solar cells

There has been great interest in recent years in using tiny particles called quantum dots to produce low-cost, easily manufactured, stable photovoltaic cells.

Now, for the most widely used type of quantum dots, made of compounds called metal chalcogenides, researchers from MIT may have found the key: The limiting factor seems to be off-kilter ratios of the two basic components that make up the dots.

The new findings — by Jeffrey Grossman, the Carl Richard Soderberg Associate Professor of Power Engineering, materials science and engineering graduate student Donghun Kim, and two other researchers — were reported this month in the journal Physical Review Letters.

There has been “a lot of excitement” about the potential for quantum dots in applications including electronic devices, lighting and solar cells, Grossman says. Among other potential advantages, quantum-dot solar cells could be made in a low-temperature process, by depositing material from a solution at room temperature, rather than the high-temperature, energy-intensive processes used for conventional photovoltaics. In addition, such devices could be precisely “tuned,” to obtain maximum conversion of specific wavelengths (colors) of light to energy, by adjusting the size and shape of the particles.

To go beyond the efficiencies achieved so far with quantum-dot solar cells, Grossman says, researchers needed to understand why the charges got trapped in the material. “We found something quite different than what people thought was causing the problem,” he says.

Giulia Galli, a professor of physics and chemistry at the University of California at Davis who was not connected with this research, says it is “quite a creative and important piece of work,” and adds that, “I'm pretty sure this will stimulate new experiments” to engineer the stoichiometry of quantum dots in order to control their properties.

In addition to Kim and Grossman, the work was carried out by former MIT postdoc Joo-Hyoung Lee, now at the Gwangju Institute of Science and Technology in South Korea, and Dong-Ho Kim of the Samsung Advanced Institute of Technology (SAIT) in Cambridge, Mass. The work was supported by SAIT, and is part of a larger quantum-dot solar cell program within the SAIT-MIT alliance that includes professors Vladimir Bulovic and Moungi Bawendi.

Source: http://web.mit.edu/newsoffice/2013/balance-key-to-making-quantum-dot-solar-cells-work-0524.html