What are LEDs and Why Use Them?

LEDs, or Light Emitting Diodes, are “solid state” electronic devices that emit light over a special, narrow waveband.

In engineering terms, LEDs, or Light Emitting Diodes, are semiconductor P-N junctions that emit light when a voltage is applied to the junction. Because LEDs are semiconductors and are made with mature semiconductor fabrication processes they are very robust. Using LEDs takes advantage of billions of dollars in research and development funding currently employed to make LEDs less expensive, more efficient and more reliable than any other form of lighting in the world.

LEDs have many advantages over conventional light sources. They are small and light weight, have very long lifetimes (depending on how they are used), can be turned on and off instantly as opposed to requiring a warm-up period, and operate on DC (direct current) as opposed to AC (alternating current). Think of DC power as standard batteries, such as AA batteries. AC power is the type found in wall outlets.

Environmentally, Psoria-Light’s LED emitter is a “green” device. Toxic gases such as Xenon and Chlorine are consumed by excimer lasers (also used to treat psoriasis, eczema, and vitiligo) and must be replaced on a regular basis. Mercury gas lamps, also a commonly used UV light source for UV phototherapy, contain mercury and must be disposed of in a special manner to accommodate their burden on the environment. Psoria-Light’s LED emitter does not consume toxic gases and does not burden the environment with mercury.

A “monochromatic” light is a light source emitting a single wavelength only. Excimer lasers approximate monochromatic light, at a peak wavelength of 308nm. “Polychromatic” light sources emit light at more than one wavelength. Elemental light sources, such as a mercury gas lamp, emit light at several different wavelengths which are specific to that element, in this case mercury.  The extraneous wavelengths of light from mercury gas lamps must then be attenuated or filtered out, adding additional heat and inefficiency.  Psoria-Shield’s LED emitter generates light at one peak wavelength, approximating a monochromatic source.

In studies evaluating specific UVB wavelengths and erythema (reddening of the skin), it was shown that:

  1. Erythema peaked at a UVB light wavelength of 297nm continuing downwards towards 280nm (minimum of UVB range), and fell off sharply above 300nm, and was least nearing 310nm and above (up and to 320nm).
  2. This means that for the same dosage of UVB light, much more erythema or reddening, sun-burn like side effects are produced in the skin at 297nm than at 310nm.
  3. As targeted UV phototherapy is based around delivering very high dosages of UV to diseased tissue, light nearing 310nm peak wavelength can be delivered in far higher dosages than light at 297nm because side effects are less near 310nm.
  4. These findings prompted the UV light industry to introduce “Narrow-Band” UVB lamps, or NB-UVB lamps, which emitted UVB light primarily between 300 and 320nm, with a peak near 310nm.
  5. Psoria-Light’s NB-UVB LEDs emit light in the 300 to 320nm region, peaking near 310nm.

Psoria-Light’s™ LED emitter issues either UVA or NB-UVB approximating monochromatic light, in a form that minimizes undesirable side effects.

Psoria-Shield chose to develop a patent pending platform to utilize deep UV LED technology versus other light source types for their:

  • Unique, single peak wavelength NB-UVB light output with little or no light below 300nm minimizing side effect
  • Small, lightweight form factor
  • Environmentally friendly, “green” technology
  • Fast switching, on / off ability, not requiring a warm-up or cool-down period

LEDs have found their way into most of the light sources we see in our everyday lives, including home lighting, traffic lights and signs, and televisions. Learn more about Psoria-Light’s fascinating deep UV LEDs and their development for and incorporation into some of the most advanced technology in the world 


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