Photoluminescence is a process in which a material absorbs photons, typically from ultraviolet or visible light, and then re-emits them as light of a longer wavelength. This phenomenon occurs when electrons in the material are excited to higher energy levels and, upon returning to their original state, release energy in the form of light. Photoluminescence is commonly observed in various materials, including semiconductors, fluorescent dyes, and phosphors. This property is widely used in applications such as LED technology, solar cells, and biological imaging. By studying photoluminescence, scientists can gain insights into the electronic and optical properties of materials, which can help in the development of new technologies and improve existing ones.