Luminescent materials are substances that emit light when excited by an external energy source, such as ultraviolet light or electricity. These materials are used in a wide range of applications, including lighting, displays, and medical imaging. The study of luminescent materials involves researching the mechanisms behind their light-emitting properties, as well as developing new materials with improved performance and efficiency. Researchers in this area work to understand the fundamental principles of luminescence and explore new ways to harness this phenomenon for practical applications.