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 – 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 – 15 | 700 – 1000 | Good | Prompt | Good | Low | Very high |
| Tungsten Halogen | 10 – 35 | 1000 – 2500 | Good | Prompt | Very good | Low | High |
| Mercury Vapour | 30 – 45 | 4000 – 6000 | Not possible | 2-5 mins | Average | Average | Average |
| CFL | 45 – 70 | 6000 – 8000 | With few lamps | Prompt | Very good | Low | Low |
| Fluorescent lamps (T12 and T8) | 40 – 60 | 5000 – 8000 | Good | 2-5 mins | Good | Low | High |
| Fluorescent lamps (T5) | 60 – 90 | 10000 – 18000 | Good | Prompt | Good | High | Low |
| Metal Halide | 50 – 100 | 6000 – 10000 | Not possible | 5 – 10 mins | Good | High | Low |
| High pressure sodium | 40 – 90 | 6000 – 12000 | Not possible | 2- 5 mins | Good, depending on product | High | Low |
| LEDs | 90 – 120 | 20000 – 30000 | Good | Prompt | Good | High | Low |
