Investigation of upconversion and downconversion fluorescence emissions from β-NaLn1F4:Yb3+, Ln23+ (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) hexagonal disk system

• Regular hexagonal disks (NaLnF4) were synthesized by a simple hydrothermal method.
• Much stronger UC and DC emissions were observed in NaLuF4-based disks.
• Stronger fluorescence emissions in NaLuF4-based disks were explained reasonably.
• NaLuF4-based disks can act as a removable luminescent platform for nano-assembly.
• NaLuF4-based disks can be applied in improving efficiency of solar cells.

Uniform hexagonal β-NaLn1F4:Yb3+, Ln23+ (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) disks were synthesized with hydrothermal method in which the sodium citrate was used as a shape modifier. The experimental observation indicated that both upconversion and downconversion fluorescence emissions were significantly stronger in β-NaLuF4 than that for β-NaYF4. It was found that the stronger hypersensitive transitions were mainly due to the increase of J–O parameter (Ω2) in β-NaLuF4 host, while the stronger insensitive transitions were mainly caused by the stronger overlap of electron cloud that was induced by the decrease of LnF bond lengths. Additionally, the larger absorption strength in the near-infrared region is another important factor for the stronger fluorescence emissions. The current research has a great potential in improving near-infrared conversion efficiency of silicon solar cells.

Well-defined β-NaLn1F4:Yb3+, Ln23+ (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) hexagonal thin disks with a simple and user-friendly hydrothermal approach by using sodium citrate as a shape modifier. Much stronger UC and DC fluorescence emissions were observed in NaLuF4-based hexagonal disks than that for NaYF4 counterparts. The strength of hypersensitive transitions is mainly attributed to the decrease of local symmetry LnF bond lengths in β-NaLuF4. It will show a great potential in improving near-infrared conversion efficiency of silicon solar cells and removable sub-micro luminescent platforms.Figure optionsDownload as PowerPoint slide