What Is Photoluminescence

Photoluminescence refers to the luminescence phenomenon produced by exciting luminescent materials with ultraviolet light, visible light, or infrared light. It roughly goes through three main processes absorption, energy transfer, and light emission. The absorption and emission of light occur at transitions between energy levels, both through excited states; while energy transfer is due to the motion of excited states. The energy of the excitation light radiation can be absorbed directly by the luminescent center or by the host of the luminescent material.

The classification of photoluminescent materials

Photoluminescent materials are classified into phosphor materials, long afterglow luminescent materials, and up-conversion luminescent materials.

Phosphor Material

The performance of phosphors directly affects the performance of white LEDs. The preparation of white light-emitting diodes is mostly inseparable from rare earth phosphors, mainly including yellow phosphors and trichromatic phosphors. Therefore, obtaining phosphors with stable chemical properties and excellent performance is the key to realizing white LEDs.

Long Afterglow Luminescent Material

Long afterglow luminescent material is a kind of photoluminescent material that can store the energy of external light irradiation under natural light or artificial light source, and then release it slowly in the form of visible light at a certain temperature (referring to room temperature). Long afterglow luminescent materials are called luminous materials or luminous materials. Long afterglow luminescent materials have important applications in low-light display, lighting, and special environments (traffic, aerospace, navigation, printing and dyeing, textiles, artwork, etc.).

Upconverting Luminescent Material

Upconversion luminescent material is a luminescent material that absorbs low-energy optical radiation and emits high-energy optical radiation. Up-transfer luminescence refers to the phenomenon in which two or more low-energy photons are converted into one high-energy photon. The light-emitting mechanism of up-conversion luminescent materials is due to the coupling effect of two-photon or multi-photon; its characteristic is that the energy of the absorbed photon is lower than that of the emitted photon, which violates Stokes' law, so this kind of material is also called anti-Stokes luminescent material.