Robust and compact artificial sunlight sources can be manufactured using low-cost LEDs and phosphors (solid-state lighting or SSL). By combining blue, violet, or ultraviolet (UV) LEDs with various phosphors covering the near-UV, visible, and near-infrared parts of the spectrum, it is possible to produce a broadband full spectrum artificial sun. This approach can even be used to manufacture tunable SSL sources with spectral emission resembling the solar output during different times of the day and at various elevations in the atmosphere, including extraterrestrial solar radiation.
For example, during sunrise, the terrestrial solar spectrum exhibits a warm color temperature and eventually rises to what is referred to as daylight color temperature in mid mornings and afternoons. At sunset, the solar spectrum reverts back to a warm color temperature. Studies funded by the US Department of Energy (DOE) have shown that people tend to be generally healthier and perform better when exposed indoors to artificial sun lighting with variable color temperature. There is also significant energy cost savings that can be achieved with lighting at variable color temperatures from tunable sunlight LEDs with spectral output that simulates the daily natural solar cycle from sunrise to sunset.
Solar spectrum LEDs have a wide range of applications that include human-centric and bio-centric lighting, scientific research, medical and health, horticulture, photovoltaic, and full spectrum LED lighting. Sun lamp therapy, in particular, is a common approach used for managing Seasonal Affective Disorder (SAD). Unfortunately, traditional solar simulator technologies are generally expensive and consume significant amounts of energy. However, with the latest PhosphorTech innovation, an artificial sun using commercial LEDs can now be achieved with proprietary down-converting phosphor systems. Although multiple UV/Vis LEDs can be integrated with different phosphors, it is also possible to use a single LED with an optimized phosphor system to deliver full spectrum lighting over a wide range of color temperatures.
Simulation of Solar Spectrum using a UVA LED and Phosphor Systems