Reductant-optimized exchange strategy to construct the water-resistant shell of Mn4+-doped phosphors

Mn-Activated Fluoride Phosphors Modified by Surfactant with Outstanding Water Resistance and Luminescent Thermal Properties

“…In other words, when the Mn 4+ ion in the phosphors is excited, the energy transfer rate between the Mn 4+ ion inside the material and the Mn 4+ ion on the surface is accelerated. The energy of the Mn 4+ ion on the surface is more trapped by the surface defect, and the energy consumed in the form of non-radiative transition is increased, while the luminescence intensity of the phosphor is weakened. , …”

“…The energy of the Mn 4+ ion on the surface is more trapped by the surface defect, and the energy consumed in the form of nonradiative transition is increased, while the luminescence intensity of the phosphor is weakened. 35,36 Therefore, the substantial enhancement of fluorescence can be attributed to two aspects: first, the addition of the surfactant CTAB during the synthesis process resulted in a reduction of material defects, reducing the unnecessary non-radiative transitions; second, the Mn 4+ concentration on the surfaces of phosphors decreased after the surface treatment of EDTA, blocking the energy transfer path and thus significantly enhancing the fluorescence intensity, the EDS mapping images can also confirm the decrease of Mn 4+ ion concentration on the material surface in Figure S1. To support this point, we also tested the fluorescence decay lifetime and quantum yield of the phosphor, which are depicted in Figure 4c,d.…”

Luminescence Enhancement of K2LiAlF6:Mn4+ Phosphors by Zn2+-Mediated Charge Compensation for Fast-Response Backlighting Applications

“…Similarly, it is found in our previous work that cutting off the energy transfer path from Mn 4+ to surface defects also exhibits a decrease in the de-excitation rate for nonradiative transitions. 28 Adachi et al found that micronizing K 2 SiF 6 :Mn 4+ phosphor particles using pulsed laser irradiation in liquid reduced the photoluminescence quantum efficiency from 0.40 to ∼0.20 and shortened the fluorescence lifetime from 9.8 to 7.6−8.7 ms. Both the decreased efficiency and faster decay are attributed to the introduction of nonradiative recombination pathways enabled by defects formed during the laser fragmentation process.…”

Advancing Red-Emitting Fluoride Phosphors for Highly Stable White Light-Emitting Diodes: Crystal Reconstruction and Covalence Enhancement Strategy

“…This limitation severely restricts their broad implementation in WLED devices. 19−22 Current strategies to address moisture resistance primarily focus on surface-based techniques, such as outer coating, 23−26 surface passivation, 27,28 and constructing a shell with minimal or no Mn 4+ presence to effectively isolate [MnF 6 ] 2− from water molecules. 29,30 Recently, our group developed a novel reduction-assisted surface recrystallization method, enabling the reconstruction of a Mn 4+ -free K 2 SiF 6 inert shell on K 2 SiF 6 :Mn 4+ crystals.…”

“…One significant challenge for ionic fluoride crystals containing [MnF 6 ] 2– is their high propensity to react with water, forming brown-black oxygen-containing compounds that drastically reduce luminescence efficiency. This limitation severely restricts their broad implementation in WLED devices. − Current strategies to address moisture resistance primarily focus on surface-based techniques, such as outer coating, − surface passivation, , and constructing a shell with minimal or no Mn 4+ presence to effectively isolate [MnF 6 ] 2– from water molecules. , Recently, our group developed a novel reduction-assisted surface recrystallization method, enabling the reconstruction of a Mn 4+ -free K 2 SiF 6 inert shell on K 2 SiF 6 :Mn 4+ crystals . The resulting core–shell structure exhibited exceptional stability, maintaining a QE of 97% even after boiling in water for 20 min.…”