Unusual concentration induced antithermal quenching of the Eu²⁺ emission at 490 nm in Sr₄Al₁₄O₂₅:Eu²⁺ for near ultraviolet excited white LEDs

Abstract

Thermal quenching of phosphor is an important challenge for its practical application in phosphor‐converted white light‐emitting diodes (pc‐WLEDs) and it usually becomes aggravated with the increase of activator concentration. Conversely, this work finds the thermal quenching of Eu2+ emission at 490 nm in Sr4Al14O25:Eu2+ does not follow this in the temperature range of 300 to 480 K, and the rate of it is even slowed down as the concentration of Eu2+ increases. However, at the same time, the experiment on three heating‐cooling cycles of Sr4Al14O25:Eu2+ reveals that the thermal degradation of Eu2+ emission becomes improved. Once Eu2+ ions are doped into Sr4Al14O25, they will prefer substituting for the 10‐ and 7‐coordinated strontium sites Sr1 and Sr2, respectively. The emission centers Eu1 and Eu2, therefore, appear. The abnormal phenomenon is perhaps partly due to the enhanced energy transfer from the emission center Eu1 at 407 nm to the one Eu2 at 490 nm. It is also found interesting that the introduction of AlN can enhance the emission of Sr4Al14O25:Eu2+ without leading to the deterioration of thermal degradation. In the end, a prototype of pc‐WLED was fabricated with Sr4Al14O25:Eu2+ to demonstrate the application of white lighting. This work is not only beneficial to the understanding of the relationship between concentration and thermal quenching, but also conducive to the design of the heavily doped phosphor for WLEDs with better resistance to thermal quenching.

Fundamental Loading‐Curve Characteristics of the Persistent Phosphor SrAl2O4:Eu2+,Dy3+,B3+: The Effect of Temperature and Excitation Density

“…It is interesting to note that biexponential fits were recently reported also for Eu‐doped Sr 4 Al 14 O 25 . [ 24 ] The authors obtained lifetimes of ≈448−301 and 45−68 ns for Eu1 and ≈729−934 ns and 146−237 ns for Eu2 (see Table S2, Supporting Information).…”

“…The traps in SrAl 2 O 4 can be intrinsic (i.e., defects in the crystal), as well as induced by the presence of B 3þ or Dy 3þ . [13,14,[19][20][21][22][23][24][25] The excitation spectra observed at 430 and 520 nm (Figure S1, Supporting Information) show that the emission at 430 nm is not excited above 410 nm, while the excitation band for the green emission extends up to 450 nm. It is thus possible to excite selectively the green-emitting Eu ion above 410 nm, while excitations at shorter wavelengths correspond to absorptions of both types of Eu ions in SrAl 2 O 4 .…”

“…The traps in SrAl 2 O 4 can be intrinsic (i.e., defects in the crystal), as well as induced by the presence of B 3+ or Dy 3+ . [ 13,14,19–25 ]…”

Stress memory for the visualization detection of complicated mechanical structures via trap structure manipulation

“…In consideration of their ionic radii, Eu 2+ , Nd 3+ , Tm 3+ are inclined to occupy Sr 2+ ions, while Mn 2+ ions locate at Al 3+ sites in the host. 32,33…”

Nanoscale Aluminate-Based Afterglow Materials from Byproducts of Aluminum–Water-Based Hydrogen Production for Anticounterfeiting and Latent Fingerprint Visualization

“…As for SAO-B, the excitation peaks are 370 nm while the emission peak is located at 496 nm due to the Eu 2+ 4f 6 5d 1 → 4f 7 transitions (Figure 4d). 49 Significantly, the average decay time is calculated as 61 s according to the eqs 1 and 2 (Figure 4e, Table S1). Even if the decay time is 180 s, the SAO-B obtained still maintains a high brightness (Figure 4e, inset).…”