photoluminescent

Photoluminescent describes materials that emit light after being excited by photons. The term covers photoluminescence, including fluorescence and phosphorescence. In fluorescence, electrons return to the ground state quickly, producing light only while the exciting source is present. In phosphorescence, some transitions are forbidden, leading to a delayed afterglow that can persist after the excitation stops.

Photoluminescent materials include organic dyes and inorganic phosphors. Many long‑lasting glow materials are doped crystalline hosts. A common example is strontium aluminate doped with europium and dysprosium (SrAl2O4:Eu2+,Dy3+), which glows for hours in green. Zinc sulfide doped with copper (ZnS:Cu) has a shorter afterglow. The brightness and duration depend on the host lattice, activator ions, particle properties, and the excitation spectrum. Efficiency is quantified by the quantum yield and the stability of the traps that store energy.

Applications include safety signage, emergency lighting, clock and instrument dials, decorative items, and certain display technologies. Photoluminescent materials are typically excited by UV or blue light, but some can use visible light. Designers choose materials based on required color, afterglow duration, and durability. Environmental and safety considerations focus on pigment composition and photostability.

Historically, photoluminescence encompasses both fluorescence and phosphorescence. In everyday usage, photoluminescent materials are those that glow in the dark after exposure. Ongoing research seeks new host lattices and activators to improve efficiency, color, and persistence for lighting and display applications.