A Light Emitting Diode (LED) generates light in a semi-conductor material, which is an electronic component. Using the right materials, a diode may produce visible light of various wavelengths.
White light is created by either using a blue diode or “chip” and adding yellow phosphor on top of it or mixing light from one red, green and blue diode (RGB). The use of phosphor conversion is the most used method in the lighting industry, due to its high efficacy and flexible production method. The phosphor can be added directly onto each diode or as a remote phosphor plate on top of a mixing chamber. This method creates a particular colour spectrum, or spectral power distribution for the LED depending on the phosphor layer.
LED is not a new invention and most of us are used to LEDs being red or green signal markers on your Hi-Fi or television set. These are so called – low-power LEDs. During the last couple of years “high power” LEDs, i.e. LEDs operating at powers of around 1 W, have reached a level of cost and performance that make them attractive to the general lighting industry.
Market studies forecast that in 2020, close to 50 % of all new and replacement light source unit sales will be based on LEDs.
Currently, the efficacy levels are at around 160 lm/W, coming out from the light source. The LED itself is expected to yield around 200 lm/W within the next ten years (Sources: McKinsey and Osram)
The spectral power distribution (how much
light that is emitted at each wavelength) of the LED mirrors the blue
light from the chip and the yellow phosphor.
This figure shows the development in efficacy (lm/W) over time for conventional and LED light sources. Whereas fluorescent tubes are expected to reach a maximum of 120 lm/W in 2020, LEDs may reach around 200 lm/W (Source: Osram)