The researchers, Mathew P. Genovese of the University of Waterloo in Canada, with Ian V. Lightcap and Prashant V. Kamat of the Radiation Laboratory and Department of Chemistry and Biochemistry at the University of Notre Dame in Indiana, will be publishing their study in an upcoming issue of ACS Nano.

The new solar paint, which the researchers humorously call “Sun Believable solar paint,” consists of a yellow or brown paste made of quantum dots. The small size of these tiny semiconductor nanocrystals makes it possible to capture nearly all incident visible sunlight with an extremely thin layer of dots. The researchers experimented with three types of quantum dots: CdS, CdSe, and TiO2, all of which are powder-like, with water and tert butanol as the solvent. As Kamat explained, all commercial paints are TiO2 nanoparticle-based suspensions. But instead of adding dye to give the paint a desired color, here the researchers added colored semiconductor nanocrystals to the solar paint to achieve the desired optical and electronic properties.

“Quantum dots are semiconductor nanocrystals which exhibit size-dependent optical and electronic properties,” Kamat told PhysOrg.com. “In a quantum dot sensitized solar cell, the excitation of semiconductor quantum dot or semiconductor nanocrystal is followed by electron injection into TiO2 nanoparticles. These electrons are then transferred to the collecting electrode surface to generate photocurrent. The holes that remain in the semiconductor quantum dot are removed by a hole conductor or redox couple and are transported to a counter electrode.”