The phrase "color-changing LED" might already sound familiar. For example, smart light bulbs often use an array of different-colored LEDs to produce a variety of hues. Similarly, the market offers a plethora of LED components designed to produce virtually any color under the Sun, on on demand. But both of these examples employ multiple LEDs of different colors packaged together to produce a desired effect. There is a new approach in development that could allow a single LED to produce more than one color, and it could signal a true revolution in displays and lighting technology.
A research team with members from West Chester University in Pennsylvania and Osaka University in Japan has described the technology in the Journal of the American Chemical Society.
A single LED, or light-emitting diode, is made by combining a semiconductor (usually silicon), with a small amount of some other substance. In a particular configuration, when electric current runs through this system, energy is given out in the form of light. The color of this light corresponds to the "distance" the electrons in the semiconductor fall as they go from an excited state to a rest state. LEDs typically only produce one color of light, intentionally exciting electrons to a particular energy state and then allowing them to drop to a particular rest energy level. However, since there can be multiple discrete energy levels for electrons in both the excited state and rest state of a given material, a single LED could be made to produce more than one color--as long as you can tell the electrons which energy state to go to.
The researchers were able to dictate the emission energy by modulating the amount of electric current running through the semiconductor. In fact, with careful tuning, they could tell some percentage of the electrons to produce one wavelength (color) of light and another percentage to produce another, which gives our eyes the illusion that intermediate colors are being produced.
The team used GaN (gallium nitride) as their semiconductor material due to its tolerance to current and its overall efficiency. GaN is quickly becoming the favorite material in numerous applications that once relied more heavily on silicon, creating more efficient devices in smaller spaces. This includes Zendure's new Passport GO Travel Adapter.
LEDs that can change color on demand could result in displays with fewer subpixels per pixel, meaning smaller pixels overall, and higher resolutions. The technology could also be employed in color-changing LED light bulbs to produce purer light tones with less flicker.
Between GaN technology and the team's work on tuning emission the energy, the future of LEDs is looking very bright indeed.