Abstract
When the bright green-emitting SrAl2O4:Eu,Dy persistent phosphor was described in the literature in 1996, this presented a real breakthrough in performance, both in terms of initial brightness and afterglow duration. Since then, many new persistent phosphors, with emission spanning from the ultraviolet to the near infrared, have been developed. Very few materials, however, reach a similar afterglow time and intensity as SrAl2O4:Eu,Dy, which is still considered the benchmark phosphor. The present paper discusses the reasons for this—seemingly—fundamental limitation and gives directions for further improvements. An overview is given of the preparation methods of persistent phosphors and their properties. Much attention is paid to the correct evaluation of a persistent phosphor in absolute units rather than vague terms or definitions. State of the art persistent phosphors are currently used extensively in emergency signage, indicators, and toys. Many more applications could be possible by tuning the range of trap depths used for energy storage. Very shallow traps could be used for temperature monitoring in, for example, cryopreservation. Deeper traps are useful for x-ray imaging and dosimetry. Next to these applications, a critical evaluation is made of the possibilities of persistent phosphors for applications such as solar energy storage and photocatalysis.
Highlights
Persistent luminescence is an intriguing phenomenon that has fascinated people for a long time
This application bears a close resemblance to the use of persistent phosphors in safety signage, but it suffers from drawbacks that are inherently related to the use of persistent phosphors under outdoor conditions
Degradation tests of Rhodamine B (RhB) and photocatalytic hydrogen evolution from water showed that the g-C3N4@Au@SrAl2O4:Eu2+,Dy3+ composite maintained some photocatalytic activity in dark conditions after irradiation for 10 min
Summary
Persistent luminescence is an intriguing phenomenon that has fascinated people for a long time. SrAl2O4:Eu,Dy. In all cases—and this is the essential difference between an “ordinary” phosphor with a decay time in the range of nanoseconds to milliseconds and a persistent phosphor—the phenomenon of persistent luminescence relies on the existence of metastable trap levels that can temporarily store the excitation energy. In all cases—and this is the essential difference between an “ordinary” phosphor with a decay time in the range of nanoseconds to milliseconds and a persistent phosphor—the phenomenon of persistent luminescence relies on the existence of metastable trap levels that can temporarily store the excitation energy In some cases, these trap levels are due to native defects, such as oxygen vacancies, but often, co-dopants like Nd3+ or Dy3+ in the abovementioned cases, are used to introduce these trap levels. The possible improvements in performance lying ahead, and challenges to be tackled, will be discussed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
