UV radiation is already largely used to disinfect water, air and surfaces, and to detect pathogenic germs, as well as for curing of synthetic materials. But a remaining challenge is the UV LED efficiency and reliability which tend to degrade over time.
Scientists from the FBH identified, amongst others, a degradation mechanism pointing to an operation-induced electro migration of hydrogen in the UV-B LED structure during the first hours of operation, which is accompanied by a drop in the optical power of the device.
After respective design adjustments, UV-B LEDs with L50 lifetimes of 8,000 hours could be demonstrated. Optimization of the devices has led to even further improvements in the reliability of the LEDs with significantly longer L50 lifetimes expected. In addition, their output power at 350 mA could be increased to 30 mW. Methods to increase internal quantum efficiency and for efficient light extraction have been investigated in detail, too.
At the conference, FBH scientists will also present a compact diode laser-based light source for the deep UV spectral range with an emission wavelength of 222nm and therefore in a region difficult to access with LEDs.
The device converts the light of a GaN-based high-power diode laser into the UV spectral range via frequency doubling (single pass) and offers the potential for miniaturization. The wavelength-stabilized, narrow-band light source is particularly suited for spectroscopy applications, such as absorption and Raman spectroscopy applied in medical diagnostics but also in substance analysis.
Supported by its Prototype Engineering Lab, the FBH is able to optimize device package for each application, tailoring complete modules to precisely fit a specific range of use. For use in greenhouses, UV LEDs need to be protected by special packages against enhanced degradation caused by the warm and humid environment.
Ferdinand-Braun-Institut manages the Advanced UV for Life consortium, co-organizer of the event, bringing together 50 partners from research and industry.
ICULTA-2018 - www.advanced-uv.de/conference
Ferdinand-Braun-Institut - www.fbh-berlin.com