Researchers at the University of Liverpool have made a discovery that could improve the conductivity of a type of glass coating which is used in items like touch screens, solar cells and energy-efficient windows.
Coatings are applied to the glass of these items to make them electrically conductive while also allowing light to go through. Fluorine-doped tin dioxide is one of the materials used in commercial low-cost glass coatings as it is able to simultaneously allow light through and conduct an electrical charge. It turns out that tin dioxide has untapped potential for improved performance.
Physicists identify the factor that has been limiting the conductivity of fluorine-doped tin dioxide which should be highly conductive because fluorine atoms substituted on oxygen lattice sites are each expected to give an additional free electron for conduction.
The scientists report that, by using a combination of experimental and theoretical data, for every two fluorine atoms that give an additional free electron, another one occupies a normally unoccupied lattice position in the tin dioxide crystal structure.
Each ‘interstitial’ fluorine atom captures one of the free electrons and then becomes negatively charged. This reduced the electron density by half and also results in the increased scattering of the remaining free electrons. These combine to limit the conductivity of fluorine-doped tin dioxide compared with what would otherwise be possible.
Jack Swallow, Ph.D. student from the University’s Department of Physics and the Stephenson Institute for Renewable Energy, said, “Identifying the factor that has been limiting the conductivity of fluorine-doped tin dioxide is an important discovery and could lead to coatings with improved transparency and up to five times higher conductivity, reducing cost and enhancing performance in a myriad of applications from touch screens, LEDs, photovoltaic cells and energy efficient windows."
The researchers intend to address the challenge of finding alternative novel dopants that avoid these inherent drawbacks.
The paper on this research was published in the journal Advanced Functional Materials.