Transparent conducting oxides are unusual but highly useful materials that combine transparency to visible light, similar to glass, with high electrical conductivity, similar to copper and other metals.
This unique combination of properties has many applications in electronics technology. For example, LEDs (light-emitting diodes) convert electrical energy to light energy, while solar cells absorb light energy and convert it to electricity. Both require electrical contacts that allow light to pass through them. Transparent circuitry is also important for flat-panel displays.
Although transparent conducting oxides have been used in technology for decades, scientists still aren’t sure how and why these materials conduct electricity. This is important, because understanding the mechanisms for their unusual conductivity could allow us to develop cheaper materials with improved properties.
Most transparent conducting oxides are produced as thin films, which are difficult to study because of the variability of their atomic structures. Single crystal specimens like those shown here (In2O3, SnO2, TiO2, VO2 and ZnO), have a more orderly arrangement of atoms, allowing us to identify more easily the structural and chemical properties that give rise to their conductivity, which we hope to understand and improve.