Near-infrared nonlinear WLEDs with high stability through atomic-level regulation and photosensitive resin encapsulating by 3D printing

Upconversion luminescence (UCL) is a nonlinear optical phenomenon where long wavelength radiation is converted to shorter wavelength via a two-photon or multi-photon mechanism. The construction of near-infrared nonlinear WLEDs can achieve effective utilization of sunlight. This work starts with "functional Motifs" and regulates the nonlinear luminescent materials at the molecular level by combining DFT calculations and high-throughput techniques. As expected, the optimized geometric structures, band structures, and density of states of Ba₂YbF₇:Ln³⁺ were successfully obtained by assembling [BaBr₄] and [LnBr₄] functional Motifs. Subsequently, Ba₂YbF₇:Ln³⁺ single phosphor was prepared and further encapsulated into resin to achieve highly stable upconversion white light using 3D printing technology. After being placed for 8 months, the luminescence intensity and spectral shape of the resin coated sample remain unchanged. The color coordinates of the WLED device constructed with Ba₂YbF₇:Tm³⁺/Er³⁺ single fluorescent powder is (0.3086, 0.3163) and the related color temperature (CCT) is 6863 K. The optimized material has a maximum color rendering index of 83. This work provides new insights and ideas for improving the luminescence stability of upconversion WLED using 3D printing technology.