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GROUP 5 : LEDS & PHOTODIODES, Light Emitting Diode(LEDs), Roles in…
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Roles in Optoelectrics
:zap:Energy Generation
In photovoltaic mode, photodiodes can generate electrical power from light, similar to solar cells.
- Solar Panels: Photodiodes can be integrated into solar energy systems to convert sunlight into electricity
:zap:Signal Processing
Photodiodes are utilized in logic circuits and detection circuits where they play a role in converting optical signals into electrical signals for further processing.
- Optical Data Communication: Enabling rapid transmission of data over optical fibers by converting light pulses into electrical signals
:star: Materials such as gallium arsenide (GaAs) are used in infrared LEDs with a relatively small bandgap (1.4 eV) suitable for emitting lower-energy, longer-wavelength light (885nm)
:star: Materials such as Gallium Phosphide (GaP) are used in visible spectrum LEDs which have a larger bandgap, (1.8 - 2.26 eV) emitting higher-energy, shorter-wavelength light (549-700nm) to produce green to red LEDs
:star: Wider bandgap materials (3.4 eV), like gallium nitride (GaN), can be used in ultraviolet LEDs (365nm).
When a forward current is applied to a compound semiconductor's pn junction, a light-emitting diode (LED) emits light. The carriers (holes and electrons) move as forward current flows through the light-emitting diode. The n-type region's electrons move to the p-type region, whereas the p-type region's holes move to the n-type region. The energy difference before and after recombination is emitted as light when the injected carriers recombine. This process is called electroluminescence. The energy bandgap (Eg) of the semiconductor material determines the color of the light that is released:
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:star: Despite their main function is emission, LEDs can also serve as simple light sensors in specific situations. An LED that has been reverse-biased may detect light by producing a little current in reaction to incoming photons. It is less effective than specialized sensors like photodiodes, though, and this sensing ability is not its main purpose.
:star: LEDs may not be as sensitive or responsive as photodiodes because they are not designed for light sensing.
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:star: The sensing function is the primary application of traditional photodiodes. Photodiodes are semiconductor devices that generate a current or voltage when exposed to light. When photons hit the depletion region of the semiconductor, they excite electrons, creating electron-hole pairs. This generates a photocurrent that is proportional to the light intensity, allowing the photodiode to detect the presence, intensity, or changes in light.
:star:Though photodiodes are typically used for sensing, some types, especially light-emitting diodes (LEDs) or laser diodes, can emit light when an electrical current is applied. This emission is achieved when electrons and holes recombine in a semiconductor material, releasing energy as photons. Although LEDs and laser diodes aren’t strictly “photodiodes,” the principle of recombination-induced emission is closely related.
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