What is Phosphor
A phosphor is a substance that exhibits luminescence when excited by certain energy sources. It is a key component used in various lighting applications, including fluorescent lamps, LEDs, and other luminescent devices.
Phosphors are typically composed of a host substance, which is often a dielectric or semiconductor material with a large band gap, and an activator substance, which is added in a specific concentration. The activator substance is commonly a rare earth or transition metal ion, such as Eu2+, Eu3+, Mn2+, Cu^+, Pb2+, Ag^+, Ce3+, or Tb3+. These ions are incorporated into the host substance to create the desired luminescent properties.
The doping concentration of the activator substance is carefully optimized to achieve a balance between efficient excitation of the phosphor and minimal reabsorption of radiated light. The goal is to obtain a sufficiently small absorption length for excitation light while avoiding excessive quenching by energy transfer processes.
Phosphors are often supplied in the form of fine powders consisting of controlled particle sizes. These powders can be applied as thin layers to allow most of the luminescent light to escape and be utilized. However, a certain thickness is necessary to ensure sufficient absorption of the excitation light or electrons.
While semiconductors used in LEDs and laser diodes also exhibit luminescence, they are generally not referred to as phosphors. Phosphors are primarily inorganic substances, although organic phosphors have been demonstrated more recently.