Paint-On Solar Cells

To fabricate solar cells, technicians may someday trade their clean-room garb for a paint smock. Researchers led by Prashant V. Kamat of the University of Notre Dame have developed “solar paints” made of a paste containing semiconducting nanoparticles (ACS Nano, DOI: 10.1021/nn204381g). The paints could lead to cheaper and easier-to-produce solar cells. Silicon-based solar cells have a high price tag because of the specialized protocols and equipment needed to make them, Kamat says. To simplify the design and lower those costs, Kamat and his colleagues wanted to develop silicon-free cells based on quantum dot nanomaterials that someone could simply paint onto any conductive surface. The team’s solar paints contain a titanium dioxide nanoparticle core coated with either cadmium sulfide or cadmium selenide. When a photon with the right energy hits the cadmium compounds, an electron escapes and TiO₂ absorbs it. The researchers found that the most efficient of these first-generation paints—with a light-to-electricity conversion efficiency of 1%—was a mixture of both CdS- and CdSe-coated nanoparticles; commercial silicon solar cells have efficiencies between 10 and 15%. Kamat and his team next plan to study paint stability, as well as work to increase the efficiency.