Design of a white-light emitting material based on a mixed-lanthanide metal organic framework

Abstract

The design of white-light emitting materials for solid-state lighting technology is governed by the combination of independent red, green and blue emitting centers. Many mixed-lanthanide single phase white-light source materials have been produced so far by a careful trial and error combination of lanthanide ions during the synthetic procedure. In this work we propose a simple and efficient method for the direct preparation of the desired material with the optimal combination of metal ions, avoiding the trial and error multiple synthetic approach. In the proposed strategy, the emission profiles of the isostructural complexes of each lanthanide ion for a chosen excitation wavelength are compared relative to their ion density and the necessary final composition of the material is calculated in order to obtain the white-light CIE coordinates. Using this method, we prepared a white-light emitting material which is a metal-organic framework built from oxydiacetate ligand, lanthanide ions (Eu, Tb and Dy emitting red, green and blue respectively) and zinc (a closed shell metal ion that has proven to be ideal for optical applications). The compound [Dy1.60Eu0.38Tb0.02Zn3(oda)6(H2O)6]·12H2O was prepared and fully characterized by single crystal x-ray diffraction, its optical properties were also measured. The proposed rational mixing of lanthanide ions could be useful for the preparation of white-light source materials in analogous systems, provided the single-lanthanide compounds are isostructural along the series and no optical interaction is operative among ions.