Unraveling the Defect-Related Luminescence in a Eu²⁺-Doped Chlorosilicate Phosphor

Abstract

Defects play non-negligible roles in many luminescent processes, where the significant and remarkable influence in the phosphor performance in various ways is observed. A full and clear perception of defects would be beneficial for the further development of the luminescence mechanism and design of phosphors. In this study, the defect-related luminescence in a chlorosilicate phosphor Ca 2 SiO 3 Cl 2 : Eu 2+ was deeply studied. Except for the green emission originating from the d−f transition of the Eu 2+ ion, a blue emission band with unique sensitivity to temperature and excitation energy was confirmed to be induced by the defects. The defects related to anion vacancies in the material acted as electron traps and luminescence centers simultaneously, which were well-identified by luminescence spectra and theory calculation analysis. This study uncovered the peculiar behavior and action mechanism of defects in the luminescence process and demonstrates a new path to understanding the origin of the luminescence center.

Highly-efficient Eu2+-activated Sr8Si4O12Cl8 cyan-emitting phosphors with zero-thermal quenching luminescence for versatile applications

“…Using the XPS results, it is shown that both Eu 2+ and Eu 3+ existed in the studied samples by substituting Sr 2+ . When Sr 2+ was replaced by Eu 2+ , the coordination situation altered, resulting in the formation of an defect, 31 in which the strontium vacancy (V′′ Sr ) was formed to maintain the charge balance. Furthermore, as for the substitution of Sr 2+ by Eu 3+ , the positive point defect was generated.…”

“…Herein, because the designed samples were prepared in a reducing atmosphere, the oxygen vacancy and the chlorine vacancy inevitably exist in the final products. 31 Because of the occurrence of these defects, they have the capacity of harvesting incident electrons, which cannot be escaped at room temperature because of the high trap depth, under NUV light excitation. Nevertheless, as the temperature increased, electrons could obtain enough energy to escape from the defect levels and populate the 5d level of Eu 2+ , and then participate in the radiative transition of Eu 2+ , as shown in Fig.…”

“…Herein, because the designed samples were prepared in a reducing atmosphere, the oxygen vacancy and the chlorine vacancy inevitably exist in the final products. 31 Because of the occurrence of these defects, they…”

“…As a branch of silicates, considerable attention has been given to chlorosilicates because of their low synthetic temperature and high physical/chemical stabilities. 31,32 Until now, different types of Eu 2+ -activated chlorosilicate phosphors, such as Ca 8 Mg(SiO 4 ) 4 Cl 2 :Eu 2+ , Ca 3 SiO 4 (Cl,Br) 2 :Eu 2+ and Ba 5 SiO 4 Cl 6 :Eu 2+ , have been developed to realize white-LED applications. [33][34][35] Moreover, Jing and co-workers, revealed that the Eu 2+ -activated Sr 8 Si 4 O 12 Cl 8 phosphors can produce a cyan emission, and they also discussed the impact of composition on the luminescence properties.…”

How to Obtain Anti‐Thermal‐Quenching Inorganic Luminescent Materials for Light‐Emitting Diode Applications

“…[74] The trap depth E T is calculated by Urbach method: E T = T m /500, where T m is peak temperature. [75] The estimated trap depths for these four glow peaks are 0.678, 0.738, 0.848, and 1.026 eV, respectively. The PL intensity of CaGa 2 O 4 :Bi 3+ under UV light excitation gradually increases with the increase of ambient temperature.…”