Generating electricity could be as easy as applying a lick of paint to the outside of your home thanks to nanotechnology research from the US. Scientists at the Notre Dame Institute in Indiana have shed light on a blend of nanoparticles that harness the Sun’s energy in the same way as a solar panel.
By using simple chemical reactions, researchers hope to create a low-cost alternative to solar panels by mixing nanoparticles within a paint. The research, described in the journal ACS Nano, and led by Professor Prashant Kamat could lead to an inexpensive way to produce electricity in the future.
Unbelievable
The paint contains nanoparticles of titanium dioxide, used to whiten toothpaste and block UV rays in sunscreen. The team coated the particles, a thousand times smaller than the width of a human hair, in cadmium sulphide or cadmium selenide. Both cadmium compounds are sensitive to visible light and increase the flow of electricity through the paint.
The resulting particles are known as quantum dots, individual crystals that release energy when stimulated by light. The scientists suspended the dots in an alcohol-water solution to create a dark yellow paint, dubbed Sun-Believable. When applied to a transparent conducting surface with a paintbrush and exposed to light, the dots absorbed photons and generated electricity. This energy was transformed into a DC current by the conducting sheet.
Solar paint
Current solar panels cells are usually made from thin films of silicon attached to a conducting plate. Sun-Believable contains millions of tiny particles that altogether add up to a much larger surface area than a continuous sheet of material. More surface area means more availability for light to electricity conversion and therefore a more productive material.
A solar cell’s efficiency is measured in how much energy is generated under test conditions that replicate sunlight on a clear day at noon. In this experimental situation a 100 cm2 solar cell with 15% efficiency would produce 1.5 watts of power. Silicon solar cells have a maximum efficiency of 37.7%, but Kamat believes the nanoparticle paint could achieve much more.
Commercially available silicon solar cells only reach 10-15% efficiency. Engineers have created better performing solar cells but they are not economical, relying on exotic materials such as gallium arsenide or indium selenide that hike the price up. A four fold increase in efficiency could therefore cost a hundred times more, negating any benefits when mass produced.
Upping efficiency
Sun-Believable did not even reach this mark, with an experimental maximum of around 1%. “If we can improve the efficiency somewhat, we may be able to make a real difference in meeting energy needs in the future,” says Kamat. “This is only the first stage.”
So far the solar paint has only been tested in lab condition, and improvements in efficiency need to be made before it can compete with today’s solar panels on large-scale building surfaces. However, the commercial viability of the concept does have precedents – nanotechnology methods have already been used to develop solar ink and printable solar technology as well as semiconductor materials, dyes and polymers.
DOI: 10.1520/G0173-03R08