Diode:
- A diode is an electronic component that has two points of contact, or terminals, called its anode and cathode.
- It is typically made from a semiconductor material, such as silicon or germanium. A diode’s primary purpose is to allow current to flow in only one direction. It achieves this using a p-n junction.
Semiconductors:
- Semiconductors are materials that have electrical conductivity between that of a conductor (like copper) and an insulator (like rubber). A diode consists of two regions of semiconductor material: the p-type region and the n-type region.
- P-type Semiconductor: A p-type semiconductor is a type of semiconductor material that has an excess of positive charge carriers (holes) and is created by introducing certain impurities into the semiconductor crystal.
- N-type Semiconductor: An n-type semiconductor is a type of semiconductor material that has an excess of negative charge carriers (electrons) and is also created by introducing specific impurities into the semiconductor crystal.
- P-N Junction: When a p-type and n-type semiconductor are joined, they form a special jone/ interface called the p-n junction.
- At the p-n junction (depletion region) when a forward voltage is applied across the diode (positive voltage at the p-type and negative voltage at the n-type), the depletion region becomes thinner, allowing current to flow easily through the diode.
- On the application of a suitable voltage across the diode, more electrons flow from the n-side to the p-side, implying an electric current flowing from the p-side to the n-side, that is from the anode terminal to the cathode terminal. But if the voltage is reversed, current won’t flow in the opposite direction.
What is an LED?
- An LED is a diode that emits light. Inside the diode’s p-n junction, the electrons have more energy than the holes. When an electron meets and occupies a hole, it releases energy into its surroundings.
- If the frequency of this energy is in the visible part of the electromagnetic spectrum, the diode will be seen to emit light. The overall phenomenon is called electroluminescence.
- In LEDs, the energy emitted when an electron and a hole recombine is the energy of the band gap.
- The colour of the light emitted by the LED depends on the energy bandgap of the semiconductor material used.
- By carefully choosing the materials that make up the p-layer and the n-layer, researchers can engineer the composite p-n junction to have a band gap that corresponds to visible light.
- LEDs can produce all three primary colours — red, green, and blue — different LEDs can be combined on a display board to produce a large variety of colours.
- Scientists were able to create red and green LEDs more than 40 years before they created blue LEDs.
- In the late 1980s, three Japanese researchers produced a bright blue LED with gallium nitride. For this feat they received the physics Nobel Prize in 2014.
Advantages of LEDs:
- Energy Efficiency: LEDs are more efficient than incandescent bulbs and fluorescent lamps. They convert a higher percentage of electrical energy into light.
- Per watt of power consumed, LEDs can produce up to 300 lumen (amount of visible light emitted per second) versus incandescent bulbs’ 16 lumen and fluorescent lamps’ 70 lumen.
- Together with their greater durability and light contrast, LEDs’ lead to higher cost savings and less material waste.
- Long Lifespan: LEDs have a much longer lifespan and durability compared to conventional bulbs. They can last up to 25 times longer, which means fewer replacements and reduced maintenance costs over time.
- Instantaneous Lighting: LEDs light up instantly without any warm-up time. They reach their full brightness immediately, which is particularly useful in applications where quick and frequent switching is required.
- Compact Size: LEDs are compact and can be made in very small sizes. This makes them versatile and allows for innovative lighting designs and applications where space is limited.
Applications:
- Lighting: Residential lighting, Commercial lighting, Automotive Lighting, Dashboard and instrument panel lighting, Backlighting for LCD screens in smartphones, tablets, and laptops.
- Electronic Displays: LED TVs and monitors, Digital billboards and signage, Information displays (public transportation, airports).
- Traffic Signals and Signs: Pedestrian crossing signals, Road signs and signal boards.
- Indicator Lights: Power indicators on electronic devices, Status indicators on appliances and equipment.
- Medical Applications: Surgical lights, Phototherapy for medical treatments.
- Horticultural Lighting: Grow lights for indoor farming and plant cultivation, Greenhouse lighting.
- UV-C Disinfection: UV-C LED lights for disinfection and sterilisation purposes, Water and air purification systems.