Light emission from excited matter that is not simply its thermal radiation at the local temperature. Fluorescence is one form of luminescence.
Electroluminescence is nonthermal light emission driven by electrical excitation. In a light-emitting diode, injected electrons and holes can undergo radiative electron-hole recombination, converting part of the supplied electrical energy into photons.
The emitted optical spectrum depends on the available transitions rather than solely on temperature, unlike an ideal blackbody. Measuring both the electric current and emitted radiant power tests conversion efficiency. Increasing electric current need not increase useful emission proportionally: nonradiative recombination, heating and extraction losses can all matter.
Photoluminescence is light emission following absorption of incident photons. The excitation first puts matter into excited states; subsequent relaxation can emit at a different wavelength. Fluorescence and phosphorescence are distinct forms whose timing and transition mechanisms differ.
An excitation source, sample, rejection filter and spectrometer form a simple experiment. Place collection optics away from the directly transmitted beam and suppress excitation light before measuring the emission optical spectrum. Recording an empty holder or solvent blank helps identify background. Emission intensity alone does not determine absorption or quantum yield, because collection geometry and nonradiative relaxation also affect the signal.
A measured emission intensity as excitation photon energy is varied, with emitted energy also selected or resolved. Excitation-emission maps can separate transitions belonging to different semiconducting carbon nanotubes.
A luminescent material, for example one that converts some of a blue light-emitting diode's light into longer wavelengths. The name does not require long-lived phosphorescence.
Articles by others on the same topic
Luminescence is the emission of light by a substance that has not been heated. It is a form of photonic emission that occurs when certain materials absorb energy and then release that energy in the form of light. This process can occur via various mechanisms, leading to different types of luminescence: 1. **Fluorescence**: A process where a material absorbs light or other electromagnetic radiation and quickly re-emits it.