Researchers have reduced the preparation time of quantum dot solar
cells to less than an hour by changing the form to a one-coat quantum
dot solar paint.
Titanium dioxide (TiO2) nanoparticles are coated with cadmium sulfide (CdS) or cadmium selenide (CdSe.) The composite nanoparticles, when mixed with a solvent, form a paste that can be applied as one-step paint to a transparent conducting material, which creates electricity when exposed to light.
Although the paint form is currently about five times less efficient than the highest recorded efficiency for the multifilm form, the researchers predict that its efficiency can be improved, which could lead to a simple and economically viable way to prepare solar cells.
The scientists responsible for the research breakthrough, 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 the American Chemical Society’s publication Nano.
During an interview with PhysOrg.com Professor Kamat, John A. Zahm Professor of Science in Chemistry and Biochemistry and an investigator in Notre Dame’s Center for Nano Science and Technology (NDnano) and who led the research, explained, “Quantum dots are semiconductor nanocrystals which exhibit size-dependent optical and electronic properties. 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. If we can optimize the paint preparation, it should be
possible for anyone to open a bottle (or a can in the long run) and
apply it to a conducting surface. This will decrease the variability
between lab to lab or person to person as one encounters in a multi-step
process. Having fewer fabrication steps and ambient preparative
conditions should provide an economically viable transformative
During their research the scientists tested a number of different compounds, but found that a composite of mixed CdS/TiO2 and CdSe/TiO2 nanoparticles performed best, particularly when the CdS and CdSe was deposited directly on the TiO2 nanoparticles as a coating.