Developed high-efficiency deep-UVLED in the US (shortest wavelength)
UV-C UV light known as the killer, with a wavelength of only 200 to 280 nm, is high in energy and can penetrate the membranes of viruses, bacteria, fungi and dust mites, attack DNA and destroy these harmful organisms.
Since Danish professor Niels Finsen discovered that ultraviolet radiation can treat tuberculosis, humans have been using UV sterilization for more than a hundred years. However, the deep ultraviolet lamps currently used are not only bulky, low in efficiency, but also contain mercury, which is harmful to the environment.
The research team at Cornell University has recently developed a small, more environmentally-friendly deep-UV LED source that sets the record for the industry's lowest wavelength of deep-UV LEDs.
The researchers used a single-layer film of gallium nitride (GaN) and aluminum nitride (AlN) as the reaction area of the atomic-level control interface to successfully emit deep-UV LEDs with wavelengths ranging from 232 to 270 nm. This 232 nm deep ultraviolet light hits the record with the shortest wavelength of light emitted by using gallium nitride as the luminescent material. The previous record was 239 nm set by the Japanese team.
The research paper "MBE-grown 232-270 nm deep-UV LEDs using monolayer thin binary GaN/AlN quantum heterostructures" was published on the January 27 issue of the Applied Physics Letters website.
Improve LED-UV efficiency
At present, the biggest bottleneck of LED-UV is luminous efficiency, which can be measured by three aspects:
1. Injection efficiency: The proportion of electron-passing devices injected into the reaction zone.
2. Internal quantum efficiency (IQE): The proportion of all electrons in the reaction zone that produce photons or ultraviolet light.
3. Light extraction efficiency: The proportion of photons produced in the reaction zone. These photons can be taken out of the device and are available.
One of the authors, Dr. SM (Moudud) Islam said: "If the efficiency of the above three aspects is 50%, only one-eighth of the multiplication is equal to the luminous efficiency has dropped to 12%."
In the deep ultraviolet range, the efficiency of these three aspects is very low, but the research team found that the use of gallium nitride instead of the traditional aluminum gallium nitride can improve the internal quantum efficiency and light extraction efficiency.
In order to improve the injection efficiency, the research team used the previously developed technology to implement the polarization induction doping method in the positive (electron) and negative (hole) carrier regions.
After successfully improving the luminous efficiency of deep-UV LEDs, the next step for the research team is to integrate the light source into the device and move toward the goal of going public. The application fields of deep ultraviolet light include food preservation, counterfeit banknote discrimination, photocatalyst, water purification and sterilization.