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

Abstract

AbstractThermal 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.