The structural characterization and its influence on photoluminescence of lithium tetra-(8-hydroxy-quinolinato) Boron

Lithium tetra-(8-hydroxy-quinolinato) boron (LiBq4) is one kind of blue light-emitting material with good performances. In this paper, LiBq4 sample was synthesized and purified. The purity is up to 97.6%. In order to investigate the influence of LiBq4 structure on its optical characteristics, especially on the shift of photoluminescence (PL) central wavelength, compared with that of tris-(8-hydroquinoline) aluminum (Alq3), a joint experiment based on a combination of X-ray diffraction (XRD) spectrum, infrared absorption (IRA) spectrum, hydrogen nuclear magnetic resonance (HNMR) spectrum, absorption and photoluminescence spectra of LiBq4 was performed. IRA and HNMR spectra generally make certain the molecular structure, and illuminate the interaction among the atoms in LiBq4. Absorption and photoluminescence spectra qualitatively suggest the basic optical characteristic of LiBq4 and that the emitted light results from 8-hydroxyquinoline rings. By comparing LiBq4 with Alq3, the conclusion that besides B−N covalent bond, B−O is another important factor which heavily influence on the PL peak can be drawn. Furthermore, the influence of LiBq4‘s special coupling manner on PL peak is demonstrated too.