Interlayer synergistic strategy to enhance the water resistance of Mn4+-doped fluoride phosphors under extreme conditions

Mn ⁴⁺-doped fluoride phosphors make a big splash in the field of WLEDs with their excellent luminescence performance. Nevertheless, the poor water resistance hinders their further development. To address such bottlenecks, this research proposes an interlayer synergistic strategy to improve the water resistance of fluoride phosphors without affecting their luminescence performance. The strategy constructs a Mn-rare shell layer with a thickness of about 700 nm as an interlayer on the surface of the K ₂TiF ₆:Mn ⁴⁺ (KTFM) phosphor, which minimizes the probability of non-radiative transitions and surface defects that makes the coating of the inorganic denser and more uniform. The treated I-KTFM sample exhibits luminescence intensity 1.06 times that of the untreated sample, with an internal quantum efficiency (IQE) of 96.76 %. Even under the extreme hydrolysis environment, it displays excellent water resistance, and the IQE remains at 91.12 %, which is superior to the treatment results of the in-situ passivation strategy (20.53 %) and the surface coating strategy (54.61 %). Moreover, the I-KTFM red phosphor is applied to the WLEDs encapsulation with an aging test, and the test results indicate that the interlayer synergistic strategy can enhance the operation stability of WLEDs, which provides a novel reference for advancing the development of high-quality WLEDs.