Identification of Dy^{3+}/Dy^{2+} as Electron Trap in Persistent Phosphors

Area of Science:

• Solid-state physics
• Materials science
• Photophysics

Background:

• Persistent luminescence (PersL) phenomena have been extensively studied.
• The underlying mechanisms, particularly electron transfer dynamics, remain a subject of debate.
• Understanding these mechanisms is crucial for developing advanced luminescent materials.

Purpose of the Study:

• To elucidate the long-standing question regarding the mechanism of persistent luminescence.
• To demonstrate and characterize the reversible electron transfer process.
• To correlate electron transfer kinetics with persistent luminescence decay.

Main Methods:

• Combined application of laser excitation and X-ray spectroscopy.
• Controlled illumination using violet and infrared light.
• Monitoring of electron transfer and luminescence properties.

Main Results:

• Demonstrated a light-controlled reversible electron transfer process.
• Observed that electron transfer kinetics match persistent luminescence decay.
• Violet light induced oxidation of excited Eu^{2+} and reduction of Dy^{3+}.
• Infrared illumination or ambient temperature facilitated detrapping of Dy^{2+}, leading to afterglow or optically stimulated luminescence.

Conclusions:

• The study confirms reversible electron transfer as the key mechanism behind persistent luminescence.
• Light serves as a controllable switch for charging and discharging the luminescent centers.
• The findings provide a fundamental understanding for designing novel persistent luminescent materials.