Gradient defects mediate negative thermal quenching in phosphors

Abstract

Luminescent materials often suffer from thermal quenching (TQ), limiting the continuation of their applications under high temperatures up to 473 K. The formation of defect levels could suppress TQ, but rational synthesis and deep understanding of multiple defects-regulated luminescent materials working in such a wide temperature range still remain challenging. Here, we prepare a negative thermal quenching (NTQ) phosphor LiTaO 3 ∶Tb 3þ by introducing gradient defects V 5− Ta , Tb 2þ Li , and ðV Ta Tb Li Þ 3− as identified by advanced experimental and theoretical studies. Its photoluminescence significantly becomes intense with rising temperatures and then slowly increases at 373 to 473 K. The mechanism studies reveal that gradient defects with varied trapping depths could act as energy buffer layers to effectively capture the carriers. Under thermal disturbance, the stored carriers could successively migrate to the activators in consecutive and wide temperature zones, compensating for TQ to enhance luminescence emission. This study initiates the synthesis of multi-defect NTQ phosphors for temperature-dependent applications.

Bismuth Vacancy-Induced Enhancement of Luminescence Intensity and Irradiation Resistance for Bi4Ge3O12

“…The atomic arrangement of Bi is discontinuous, blurred, and even missing in lattice fringes, indicating the existence of vacancy defects. The same phenomenon has been found in other materials with abundant defects. ,, The crystal model viewed along the [4̅6̅3] zone axis is presented in Figure h. Also, the intensity distribution recorded along L1 verifies the existence of the Bi vacancy (Figure i).…”

“…The same phenomenon has been found in other materials with abundant defects. 15,17,18 The crystal model viewed along the [4̅ 6̅ 3] zone axis is presented in Figure 1h. Also, the intensity distribution recorded along L1 verifies the existence of the Bi vacancy (Figure 1i).…”

Stimulated-source-independent persistent luminescence phosphor Sr2Ta2O7:Tb3+, Tm3+ for multi-mode anti-counterfeiting applications

“…8,9 In response to this, luminescent materials have been combined with a variety of stimulation modes using different methods, and multi-mode luminescent anti-counterfeiting materials came into being, which were usually easily copied mixture combinations or possessed a complicated core-shell structure. 10,11 To further improve the security level of information encryption, more advanced single-phased multimodal luminescent materials have been designed based on their responses to multiple excitation/stimuli sources, 12 and they are difficult to imitate due to the integration of numerous excitation modes in one. 13 The most popular strategy is integrated up-/downconversion into one host to achieve various color emissions.…”

“…8,9 In response to this, luminescent materials have been combined with a variety of stimulation modes using different methods, and multi-mode luminescent anti-counterfeiting materials came into being, which were usually easily copied mixture combinations or possessed a complicated core–shell structure. 10,11…”

Crystal Field Engineering of Pr-Activated Gehlenite with Near Golden Ultraviolet C Emission for 100% Sterilization Efficiency

“…These results indicate that the DTs content can be increased by doping Sr 2+ . An empirical method is applied to estimate the trap depths from the location of TL peak: − italicE normalD = italicT normalm 500 in which E D is the average energy trap depth and T m (K) is the peak temperature. The calculated depths of STs and DTs are about 0.7 and 0.96 eV, respectively.…”