Up-conversion charging of a Tb³⁺-activated garnet phosphor

Abstract

Studies on up-conversion charging of persistent phosphors are of great academic and practical significance. To date, up-conversion charging designs have been achieved in Cr3+, Mn2+ and Pr3+-activated phosphors. We herein...

Lanthanide-doped Na2MgScF7 exhibiting downshifting and upconversion emissions for multicolor anti-counterfeiting

“…The PLE spectra of NMSF:5%Tb 3+ monitored at 543 nm consist of a strong band from 200 to 300 nm with a maximum at 219 nm, which can be attributed to the 4f 8 → 4f 7 5d 1 transition of the Tb 3+ ions and the bands in the range of 300–400 nm are derived from the 4f → 4f transitions of the Tb 3+ ions. 9 Under excitation at 254 nm, the PL spectrum of the Tb 3+ ions consists of four emission bands centered at 488, 544, 587 and 623 nm originating from the transitions of the Tb 3+ ions from the 5 D 4 excited state to the 7 F J ( J = 6, 5, 4, 3) ground states. 39,40 The CIE chromaticity coordinates of the emissions are (0.2744, 0.4475), indicating that the emission color is yellow-green.…”

“…The Tb 3+ ion is known for its strong green emission with a transition from the 5 D 4 to 7 F 5 energy level. [9][10][11][12][13] The Eu 3+ ion usually emits strong red light, and the emission wavelength range is 550-650 nm, corresponding to the transition of the 5 D 0 to 7 F n energy level. [14][15][16] On the basis of the ladder-like energy levels, some of the lanthanide ions can realize UC emission, which can convert two or more lowerenergy photons into one higher-energy photon.…”

Excitation Strategy of Infrared Persistent Phosphors via Upconversion Charging and Persistent Energy Transfer

“…Subsequently, to further gain insight into the UCC of the LMG:Cr,Yb,Ni phosphors, we study the mechanism that accounts for the upconversion excitation by carrying out an extensive thermoluminescence measurement. During the UCC in the phosphor, in principle, an excited-state absorption or an energy-transfer upconversion mechanism is involved in the two-step excitation. , In either mechanism, upon illumination with the flashlight, the intermediate state of Cr 3+ will be populated first. If the excited-state absorption dominates the UCC excitation process, it is expected that the intense flashlight illumination can promote the Cr 3+ from the intermediate state upward to the high-energy delocalized state.…”

“…To date, several low-energy excitation approaches for persistent phosphors have been put forward, in which upconversion charging (UCC) has emerged as an interesting candidate for charging the phosphors using long-wavelength excitation light. − It is by now generally accepted that the trap in a phosphor is filled via a two-step ionization of an activator in a typical UCC process. , Moreover, according to the mechanism of UCC, the activator ions should have a tendency to be oxidized in a UCC phosphor. − Such a prerequisite limits the choice of activator ion for the UCC design. As candidates for infrared emitting centers in persistent phosphors, rare-earth ions (e.g., Pr 3+ , Nd 3+ , Ho 3+ , Er 3+ , Tm 3+ , or Yb 3+ ) and transition-metal ions (e.g., Cr 3+ , Mn 4+ , or Ni 2+ ) have been reported. − ,− However, many of these ions have no tendency to be oxidized in phosphors and thus do not satisfy the prerequisite for UCC.…”

Dy3+ and Tb3+ codoped mixed garnet crystals with a high-disorder structure for promising efficient InGaN laser-diode pumped yellow lasers

“…Moreover, the absorptions in the visible region, specifically Dy 3+ : 6 H 15/2 → 4 F 9/2 + 4 I 15/2 + 4 G 11/2 and Tb 3+ : 7 F 6 → 5 D 4 , are spin forbidden, resulting in weak absorption intensities in this range. [37][38][39] Regarding the NIR region, Tb 3+ primarily contributes to absorptions above 1800 nm, corresponding to its 7 F 6 → 7 F J ( J=0, 1, 2) transitions. The absorptions within the range of 800 to 1750 nm are attributed to the transitions of Dy 3+ from its ground state 6 H 15/2 to various excited states.…”