Definition of photoluminescence

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Photonics Dictionary

photoluminescence: Photoluminescence is a phenomenon in which a material absorbs photons (light) at one wavelength and then re-emits photons at a longer wavelength. This process occurs when electrons in the material are excited to higher energy states by absorbing photons and subsequently return to lower energy states, emitting photons in the process. The emitted photons have less energy and longer wavelengths than the absorbed photons.

Photoluminescence can be broadly categorized into two types:

Fluorescence: In fluorescence, the excited electrons return to their ground state (lowest energy state) relatively quickly, typically within nanoseconds to microseconds after absorption. This rapid decay results in prompt emission of photons, making fluorescence useful for various applications such as biological imaging, fluorescence microscopy, and sensing.

Phosphorescence: Phosphorescence involves a longer-lived excited state, with electrons returning to the ground state over a longer timescale, ranging from milliseconds to hours or even longer. As a result, phosphorescent materials continue to emit photons after the excitation source is removed. Phosphorescence is used in glow-in-the-dark materials, phosphorescent paints, and certain types of organic light-emitting diodes (OLEDs).

Photoluminescence occurs in a wide range of materials, including semiconductors, organic compounds, phosphors, and quantum dots. The specific wavelengths of light emitted during photoluminescence depend on the energy band structure and electronic transitions within the material. By analyzing the emitted light, researchers can gain insights into the electronic and optical properties of the material, such as bandgap energy, defect states, and impurities.

Photoluminescence spectroscopy is a powerful technique used in materials science, chemistry, physics, and biology for characterizing and studying various materials and compounds. It provides valuable information about the composition, structure, and behavior of luminescent materials, enabling applications in fields such as optoelectronics, photovoltaics, light-emitting devices, and quantum technologies.