University of Toronto investigators have designed a new type of nanoparticle that could replace big, bulky solar cells for energy production. 

Colloidal quantum dots could be used to manufacture a new generation of solar panels that would be both flexible, and less expensive than contemporary designs. The nanoparticles could even be mixed into paint, and spread on roofs, ready to collect sunlight. This could allow the low-cost installation of solar cells in areas where installation of traditional designs prove uneconomical. 

Quantum dots depend on two types of materials to function, converting sunlight to electricity. One of these are n-type material, which are rich in negatively-charged elections. The other variety, p-type, have few electrons, and possess a positive charge. When traditional dots are exposed to air, the n-type materials react with oxygen, and lose some of their electrons, becoming p-type. This new model does not react with oxygen, greatly increasing the versatility of the new design. 

"This is a material innovation, that's the first part, and with this new material we can build new device structures. Iodide is almost a perfect [atom to bind with metal] for these quantum solar cells with both high efficiency and air stability - no one has shown that before," Zhijun Ning, post-doctoral researcher and co-leader of the research, said. 

Potential uses for the new nanoparticles also include new infrared LED's and lasers, in addition to remote controllers, pollution detectors, and better gas sensors. For commercial uses, the components manufactured from this design could improve satellite communications and weather observations. 

The new technology still has a way to go before it can compete with traditional designs in terms of efficiency. At eight percent efficiency, the tiny cells are significantly less efficient that the 20 to 30 percent available in traditional models. The lower cost and greater versatility of nanoparticles could be revolutionary, if they could generate even a little more power. 

"The field has moved fast, and keeps moving fast, but we need to work toward bringing performance to commercially compelling levels," Ted Sargent, who led the team with Ning, said in a university press release. 

One drawback to the new design is that they cannot convert much of the infrared part of the spectrum, which we sense as heat from the sun, into energy. Half of the energy that reaches us from our stellar companion is in the form of these infrared waves. The new design tunes plasmonic nanoparticles to these frequencies, creating additional energy. 

Development of the new technology for solar cell construction was detailed in the journal Nature Materials.