Solar paint

(Nanowerk News) What if all it takes is a coat of paint to convert light energy into electricity? A new generation of photovoltaics will bear no resemblance to the rigid solar panels installed on house roofs. Working with semiconductor nanoparticles synthesized in solution, researchers – analogous to 'electronic ink' – are creating 'solar paints' that can be applied to virtually any structure, similar to regular paint.
Because of the extremely small size of semiconductor quantum dots and high absorption cross section, it is possible to capture nearly all of the incident solar light in the visible region with an extremely thin layer of semiconductor materials. These heterojunction semiconductor solar cells offer new opportunities to develop relatively inexpensive solar cells.
A 'solar paste' of cadmium sulfide-coated titanium dioxide nanoparticles
A 'solar paste' of cadmium sulfide-coated titanium dioxide nanoparticles.
One approach, developed by researchers at the University of Toronto and King Abdullah University of Science and Technology (KAUST), uses colloidal lead sulfide (PbS) quantum dots that can be used to harvest electricity from the entire solar spectrum because their energy levels can be tuned by simply changing the size of the particle. As we have reported previously ("Solar paint paves the way for low-cost photovoltaics"), this solar cell ink that can be deposited in a single step which makes it an excellent material for high-throughput commercial fabrication.
A similar approach has been developed at the University of Notre Dame, where researchers have developed a paste of cadmium sulfide-coated titanium dioxide nanoparticles that could turn large surfaces into solar cells (read more in our article "Researchers develop paint-on solar cells").
A major drawback of these solar paints is their low efficiency. The best light-to-energy conversion efficiency that has been reached so far is 1 percent, which is well behind the usual 10 to 15 percent efficiency of commercial silicon solar cells.
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