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Photonics Dictionary

quantum efficiency

Quantum efficiency (QE) is a measure of the effectiveness with which a device or system, typically in the context of photonics or electronics, converts incoming photons (light) into a useful output signal or response. It is expressed as a ratio or percentage and quantifies the number of electrons or charge carriers generated in response to the incident photons. In other words, quantum efficiency provides a measure of how well a device can capture and utilize photons to produce an electric current, voltage, or some other desired outcome.

Quantum efficiency is often used in various fields, including:

Photodetectors: In photodetectors, such as photodiodes or photomultiplier tubes, quantum efficiency indicates the ratio of electrons generated to incident photons. Higher quantum efficiency means a more sensitive and efficient photodetector.

Solar cells: For solar cells or photovoltaic devices, quantum efficiency is used to measure the percentage of incoming sunlight that is converted into electrical energy. Higher quantum efficiency is desirable for more efficient solar energy conversion.

Imaging sensors: In the context of image sensors, like charge-coupled devices (CCDs) or complementary metal-oxide-semiconductor (CMOS) sensors, quantum efficiency represents how well the sensor captures and converts photons into electrical signals, which directly impacts image quality in digital cameras.

Quantum dots: Quantum efficiency is also important when working with quantum dots or other nanomaterials that can absorb and emit light, as it quantifies their ability to convert absorbed photons into emitted photons.

Quantum efficiency can be wavelength-dependent, as some devices may have varying efficiencies at different wavelengths of light. It is typically expressed as a percentage or a decimal value ranging from 0 to 1, where 1 (or 100%) would indicate perfect efficiency, meaning that every incident photon is converted into a useful signal. In practice, achieving quantum efficiencies of 100% is rare, and the actual quantum efficiency of a device depends on its design, materials, and operating conditions.

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