With an increase in the type of ultraviolet (UV) light applications, the specific requirements for various industries are growing and there is a greater emphasis on higher light output, better thermal management, greater flexibility, and more adaptability. Companies require sophisticated, customized solutions to revitalize their business and industries such as horticulture, curing, and disinfection are making significant changes as they see a growth in research and development in UV technologies. While ultraviolet light has been used extensively for more than 40 years, ultraviolet light-emitting diodes are a promising entry offering a more sustainable solution than the incumbent lamp technologies. UV LEDs have risen to answer the current technological limitations with mercury lamp sources and hold the key to growth in industries worldwide. With a flexible form factor and an inherent ability for intensity and spectral control, UV LEDs can be integrated into various systems across several different applications.
UV wavelengths can be divided into 3 different bands: UVA, UVB and UVC. Some wavelengths within these spectral bands are more popular than others for UV LED applications. For example, in pandemic situations (Coronavirus in 2020), the need for disinfection devices increased significantly and so the demand for 265 and 280 nm LEDs was significantly escalated [1] due to their ability to inactivate microbes even at low dosages. In terms of pricing, the cost of UV LEDs increases for shorter wavelengths in the UVC band due to the material challenges and lower efficiency associated with the technology.
While the high costs and lower efficiencies of UV LEDs at this time present a challenge, trends for an increased efficiency, market adoption of this technology and the rise in niche applications do promise a brighter future for this technology. UV LEDs offer the potential to push these markets into their future, through continual improvements in light output, flexibility, reduced costs, and environmental impact.
Compared to traditional UV solutions, UV LED have improved upon every aspect of UV performance, such as light output, lifetime operation, energy efficiency, thermal management, and usability. In the coming years, traditional UV sources are expected to be widely replaced by LED technology and this would further enhance the investment in this technology to break research barriers. In this article, we will look at the status of UV LEDs in terms of their current and projected market, the efficiency increases over time and a comparison with UV lamps, hence providing motivation for the further development and adoption of this technology.
Figure 1 shows the market projection for different wavelength ranges for UV LEDs based on Trendforce report 2020 [2]. These values were projected in 2019, before the start of the Coronavirus pandemic but the adoption of UVC technology may have seen a greater rise in 2020 due to the emergence of several disinfection products.
While the market for UV LEDs is expanding, the price/mW has also reduced and is expected to decrease even further as shown in Figure 2. The significant drop in UVC pricing in 2020 has been fueled by the acceleration in mass production and increase in optical power. The demand for UVC LEDs has seen a sudden surge in 2020 due to the COVID-19 pandemic.
In terms of the light output, 100mw UVC LEDs, which seemed to be a target for the future, are now available commercially. Figure 3 shows the optical output vs. drive current for commercially available UVC LEDs in 2021. While optical output improvements are rapidly bringing in new applications for LEDs, component lifetimes and reliability drive the adoption into commercial product development.
UV light emitted by mercury lamps has been the primary light source available for decades. However, environmental awareness on the use of mercury-based lamps and international treaties such as the Minamata convention have fueled the need for non-mercury sources. With rapid advancement in UV LED technology, the benefits of a smaller, more robust, mercury-free, long lifetime, energy efficient light source have been understood.
While medium-pressure mercury lamps emit a broadband spectrum, low pressure mercury lamps emit an almost monochromatic light with a wavelength of 254 nm. This wavelength, while widely utilized for disinfection applications, does not find use in many other applications which the UV LED enables due to a targeted very specific and narrow wavelength emission as shown in Figure 4.
When considering applications related to disinfection with UVC LEDs, the narrowband peak wavelength of a 265 nm LED more closely matches the peak absorption wavelength of most bacteria and viruses, thus allowing for more efficient rates of disinfection (in comparison to a broadband or a 254 nm light source source). The advantages of a narrow wavelength emission have also led to the growth of innovative and targeted solutions in the fields of curing, spectroscopy, biomedical instruments, and more.
The compact form factor of the UV LED allows for increased design flexibility in comparison to the existing lamp solutions on the market. While UV lamps have a cylindrical form factor, the directional output of UV LEDs allows for more uniform distribution of light over larger areas. UV LEDs can also be arranged in a wide variety of configurations to achieve high uniformity and targeted illumination of a given exposure area. LED irradiance profiles can be tuned by using beam shaping optics. The compact size of UV LEDs has additionally opened up integration of UV in products such as battery-powered portable electronics, point-of-use water disinfection, and more.
Although UV lamps are suitable solutions for applications that require high intensity, continuous operation, they require a warm-up period and have reduced lifetimes if cycled frequently. UV LEDs offer instant UV flux that can be cycled on-off with low lifetime degradation. They can be controlled more effectively by dimming the light intensity initally and increasing it as the LED ages, allowing for extended use over long periods.
Although initial investment costs are currently higher for UV LEDs, the overall operational costs and usage conditions must be considered to select the appropriate solution over the long term. UV LEDs require little maintenance and can be operated with smaller, less complex, and more affordable electronics, thus allowing for potential reductions in cost when considering the entire system over its lifetime. Table 1 shows a comparison of spectral output of UV LEDs and mercury lamps. The spectral output is determined relative to the individual source for UV LED wavelengths.
Comparison
UV LED
UV Lamp
Spectral Output
Single peak wavelength
Broadband with multiple peaks
Light Output Stability
Excellent
Comparatively poor
Warm-Up Time
Zero
Up to 15 minutes
Forward Heat Generation
No
High
Driving Mechanism
Simple
Complex
Environmentally Friendly
Yes
No, Mercury content
Optical Angle Shaping
Yes
No
Design Flexibility
High
Low
Product Size
Compact
Large
Lifetimes
Up to 40,000 hrs
Up to 12,000 hrs
Table 1: Comparison of the UV LED and the broadband UV lamp
In terms of the application, UV LEDs have certainly made a mark in the water disinfection market for point of use applications. Due to the small form factors and flexibility of design, LEDs are also finding application in niche markets. Table 2 shows some of the primary applications of UV LEDs, the corresponding UV bands and the strength of the UV LEDs which makes them an optimal source for these applications.
Primary Applications
Usage
UV Bands
LED Strengths
Water Disinfection
• Point-of-use
• Faucets
UVC
Small form factor, mercury free option, shatter-proof, no warm-up times
Air Disinfection
• In-duct use
• Upper air disinfection
• Localized recirculation
UVA/UVC
Small form factor, design flexibility, chemical free, no warm-up times
Food Safety and Preservation
• Produce disinfection
• Extension of shelf life
UVC
Chemical free, shatter-proof
Surface Disinfection
• Portable units
UVC
Beam angle and intensity control, no warm-up times
Horticulture
• Pest-control
• Nutritional improvement
UVB
Can be combined with visible wavelengths on the same device
Phototherapy
• Dermatology needs
UVB
Small form factor
Sensing
• Gas sensing
UVC
Spectral bands available, narrow spectral output
UV Curing and 3D Printing
• Polymers
• Adhesives and coatings
UVA/UVC
No warm-up times, less down-times, lower forward heat-generation, high uniformity possible using controllable beam angles
This work was performed at University of British Columbia to develop a modular, energy-efficient, and spectrally tunable lighting system for photochemical experiments for simulating stratospheric, tropospheric and indoor light conditions.
This technical application note provides information on Violumas’ ultra-narrow beam lenses and their use in UV LED systems. It introduces the underlying optical principles, key performance considerations, and potential applications of Violumas’ ultra-narrow beam angle – the Viobeam Product. The document is intended to help users understand how these lenses can be used to achieve precise, focused UV illumination in demanding applications.
