Air and Thermally Stable Fluoride Bridged Rare‐Earth Clusters Showing Intense Photoluminescence and Potential LED Application

Abstract

Fluoride based lattice is attractive for reducing phonon‐induced quenching in rare‐earth (RE) based luminescent materials. However, due to the strong affinity between RE and oxygen, the synthesis of fluoride‐based complexes has to be protected under anhydrous conditions, and many known fluoride bridged RE clusters are unstable in air. Here, by using the “mixed‐ligand” strategy a family of fluoride bridged RE clusters is synthesized, namely RE16(μ4‐F)6(μ3‐F)12(tBuCOO)18[N(CH2CH2O)3]4 (RE = Eu, EuFC‐16; RE = Tb, TbFC‐16), which are highly stable in air and decomposed thermally only when heating above 435 °C. Moreover, both clusters exhibit high photoluminescence quantum yields (PLQYEuFC‐16 = 87.7%, PLQYTbFC‐16 = 99.0%). Upon warming, EuFC‐16 and TbFC‐16 display excellent structural, thermal, and chroma stability. Thus, EuFC‐16 and TbFC‐16 have the potential to be used in light‐emitting diode (LED) devices, offering many advantages over commercial phosphors. First, both clusters are soluble in UV‐curable resin at any mixing rate, and the emission colors can be tuned from magenta, turquoise, willow green, and ivory to pure white if mixing blue phosphor BAM:Eu2+. Second, the clusters are hydrophobic, and the LEDs work well after soaking in water, indicating a good quality for outdoor lighting.