Notes On Optoelectronic junction devices - CBSE Class 12 Physics
Optoelectronic junction devices are p-n junction devices in which, carriers are generated by photons. Photodiodes, light emitting diodes (LEDs) and solar cells are examples of optoelectronic devices. A photodiode is a device that is used to detect optical signals. It is a specially fabricated p-n junction diode, with a transparent window that allows light to be incident on the diode. The magnitude of the photocurrent is too small compared to the large current that flows through the diode under forward bias. Thus, a photodiode is always operated under reverse bias. A light emitting diode or an LED is a device that produces photons of different frequencies of light. An LED is operated under forward bias. The energy of the emitted photons, and the colour of the light produced, depends on the nature and the band-gap of the semiconductor material used in the LED. LEDs offer several advantages over conventional electrical light sources: · Low operational voltage and power consumption · Instant on-off switching without any warm-up time · Source of near monochromatic light · Long life and negligible wear and tear A solar cell is a device that converts light energy into electrical energy. A solar cell works on the same principle as that of a photodiode, where incident light generates electron-hole pairs in the depletion region of the p-n junction. Unlike a photodiode, a solar cell works without any external bias. The large surface area of the p-n junction in a solar cell generates measurable photocurrent making it a source of electricity. The photocurrent produced by a solar cell depends on the intensity of the incident light.

#### Summary

Optoelectronic junction devices are p-n junction devices in which, carriers are generated by photons. Photodiodes, light emitting diodes (LEDs) and solar cells are examples of optoelectronic devices. A photodiode is a device that is used to detect optical signals. It is a specially fabricated p-n junction diode, with a transparent window that allows light to be incident on the diode. The magnitude of the photocurrent is too small compared to the large current that flows through the diode under forward bias. Thus, a photodiode is always operated under reverse bias. A light emitting diode or an LED is a device that produces photons of different frequencies of light. An LED is operated under forward bias. The energy of the emitted photons, and the colour of the light produced, depends on the nature and the band-gap of the semiconductor material used in the LED. LEDs offer several advantages over conventional electrical light sources: · Low operational voltage and power consumption · Instant on-off switching without any warm-up time · Source of near monochromatic light · Long life and negligible wear and tear A solar cell is a device that converts light energy into electrical energy. A solar cell works on the same principle as that of a photodiode, where incident light generates electron-hole pairs in the depletion region of the p-n junction. Unlike a photodiode, a solar cell works without any external bias. The large surface area of the p-n junction in a solar cell generates measurable photocurrent making it a source of electricity. The photocurrent produced by a solar cell depends on the intensity of the incident light.

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