Single Molecule Electroluminescence
- by Anton Skorucak and ScienceIQ.com
There are two main ways to make light. In incandescence, something is heated until it glows, like the filament of an old-fashioned light bulb, a toaster coil, or the Sun. Any other way of producing light, without high heat, is called luminescence, or "cold light." There are several kinds, named after the energy that powers them.
- Photoluminescence is powered by light. Glow-in-the-dark toys soak up light and slowly release it (phosphorescence), and highlighters and laundry whiteners glow brightly under ultraviolet "black light" (fluorescence).
- Chemiluminescence is powered by a chemical reaction. Bend a glow stick and two chemicals mix and give off light. When living things do this, like fireflies and many deep-sea fish, it is called bioluminescence.
- Electroluminescence is powered by electricity. An electric current or field excites the electrons in a material, and they release their extra energy as light.
Electroluminescence is now all around us. Light-emitting diodes (LEDs) have largely replaced incandescent bulbs because they turn much more of their electricity into light instead of waste heat. The OLED (organic LED) screens in many phones and TVs are made of thin films of carbon-based molecules that glow when current flows through them, and flat electroluminescent panels light up night lights and watch faces.
Scientists have also pushed electroluminescence down to incredibly small scales. In the early 2000s, a team led by Robert Dickson at the Georgia Institute of Technology made thin films of silver oxide glow from clusters of just a few silver atoms. After activating the film with a direct current, they connected electrodes carrying alternating current, and tiny spots in the film began to emit light, in colors that depended on the size of each cluster. Zooming in, they could see the light coming from individual nanoclusters. Research like this may lead to tiny light sources built right into computer chips, and to new kinds of optical memory and secure quantum communication.
