Recently, the research team of Professor Yang Yanmin, School of Physics, Hebei University and Professor Qiu Jianrong of Zhejiang University have proposed the long afterglow luminescence mechanism of trivalent rare earth ions doped broadband gap matrix, and considered that the medium electron trap binding exciton plays an important role in the interband charging process, and successfully designed and realized the ultra-long afterglow emission of Gd3+.
Long afterglow luminescent materials have been widely used in luminous display, lighting, safety marking, biological imaging and other fields. However, the basic physical mechanism of long afterglow luminescence is still controversial, which leads to the development of long afterglow materials still using the trial and error method of cooking. In this work, the long afterglow luminescence mechanism of trivalent rare earth ions doped wide band gap matrix is proposed. The interband charge excites the valence band electrons to the conduction band, and the conduction band electrons and the valence band holes in the high band gap matrix attract each other to form stable excitons at room temperature. Excitons may also participate in the process of energy transfer. The obtained data show that excitons can transfer energy to the luminous center and produce light emission. In this paper, it is pointed out that the ability of rare earth ions to bind carriers is not only related to their own electron arrangement, but also related to the characteristics of substitution cations and coordination anions. The reason why Er3+, Nd3+, Ho3+ and Gd3+ are not easy to produce afterglow is their weak carrier-bound ability caused by their own electron arrangement. The ultra-long afterglow of Er3+, Nd3+, Ho3+ and Gd3+ was successfully realized by changing the substitute cations and coordination anions. The isoelectronic trap bound carrier model can be used not only for the afterglow design of rare earth ions, but also for the prediction of afterglow emission properties of transition and even main group elements, so as to provide a theoretical basis for the design of new long afterglow materials.
