Light emitting diodes is a solid state lighting system based on p-n junction semiconductor crystal where photons are generated through radiative recombination through charge carriers (electrons and holes). The system is in line with semiconductor diode which is formed by combining p- and n-type materials together to form a junction. The combination forms a layer of ionized acceptors in the p-side and another layer of ionized donors in the n-side forming a potential junction. With electric current across the junction, the electrons will get energized to jump from the one layer and recombine with the holes emitting a photon. Average life time expectancy of LED is 15,000 to 25,000 hours with a CRI ranging from 50 โ 90. Such a wide range of life expectancy and CRI is because the product is in a nascent stage of its development and no standards are available in the market for a uniform manufacturing.
Key advantages:
- Small in size and robust in design
- Long life time expectancy
- No toxic content and easy to recycle
- Has short start and re-starting time
- High luminous efficacy
- Low heat load
Key disadvantages:
- High price
- Low luminous flux
- Risk of glare
- No standards are available for product manufacturing
Luminous efficacy | Lamp life (Hours) | Control integration | Re-strike time | CRI | Price of product | Cost to operate | |
Incandescent | 5 โ 15 | 700 โ 1000 | Good | Prompt | Good | Low | Very high |
Tungsten Halogen | 10 โ 35 | 1000 โ 2500 | Good | Prompt | Very good | Low | High |
Mercury Vapour | 30 โ 45 | 4000 โ 6000 | Not possible | 2-5 mins | Average | Average | Average |
CFL | 45 โ 70 | 6000 โ 8000 | With few lamps | Prompt | Very good | Low | Low |
Fluorescent lamps (T12 and T8) | 40 โ 60 | 5000 โ 8000 | Good | 2-5 mins | Good | Low | High |
Fluorescent lamps (T5) | 60 โ 90 | 10000 โ 18000 | Good | Prompt | Good | High | Low |
Metal Halide | 50 โ 100 | 6000 โ 10000 | Not possible | 5 โ 10 mins | Good | High | Low |
High pressure sodium | 40 โ 90 | 6000 โ 12000 | Not possible | 2- 5 mins | Good, depending on product | High | Low |
LEDs | 90 โ 120 | 20000 โ 30000 | Good | Prompt | Good | High | Low |