Phosphor with long-lasting phosphorescence (LLP) properties of a class of luminescent materials that absorbs energy and then releases the stored energy in the form of light after excited. The released luminescent light can last several of hours. This materials are attract the interest of our research group due to their various applications, such as lighting display, detection of high-energy rays (e.g UV, X-ray and gamma-ray), multidimensional optical memory, and imaging storage. As potential candidate for replacement for replacement of conventional incandescent and fluorescent lamps, due to its advantages such as long lifetime, lower energy consumption and higher reliability, in addition to search good material mercury-free fluorescence lamp. Theoretically, LLP originate from the thermal stimulated recombination of holes and electrons stored in traps, the long lived excited state at room temperature. It is expected that the LLP can be observed from the phosphors if there exist adequate hole traps and electron traps with suitable depth. Based on this principle, our researcher group studies in this field have (and will) developed various kinds of LLP phosphors with different lattice host and different activators. The aims of our research group are:
1. Involves exploring many aspects of electronic energy level structures of rare-earth-activated optical materials and requires a wide variety of experimental techniques. The purpose of this work is to gain a complete picture of the electronic structure of these materials that includes understanding the relationships between the 4fN levels, 4fN-15d levels, and the host crystal’s valence and conduction bands. This research is motivated by the need to improve our fundamental understanding of these materials as well as gain practical knowledge of immediate use in developing new rare-earth-activated optical materials for lasers, phosphors, scintillator, and optical computing applications
2. A thorough understanding of both static and dynamic properties of the electronic structure of rare-earth-activated optical materials is needed to guide the search for new materials that satisfy all of the requirements for phosphors, scintillators, and the many other rare-earth enabled optical technologies. To improve our understanding of these materials, a variety of experimental techniques are employed and coupled with theoretical modeling of the observed properties. Thus, high-resolution linear and non-linear spectroscopy of the intra-configurational 4fN to 4fN-15d transitions, and photo-ionization and electron photoemission spectroscopy of the 4f electrons and host states are all employed to map out the energy levels and interactions that are crucial for technological applications as well as for a fundamental physical understanding of rare-earth-activated optical materials.