Tris(2-Acyl-1,3-indandionate)aluminum(III) complexes as emitting layer in electroluminescent devices

Abstract

This work reports about syntheses, characterization, Photo (PL) - and electroluminescence (EL) properties of the complexes presenting general formula [Al(aind)3], where aind: 2- acetyl-1,3-indandionate (acind), 2-propyl-1,3-indandionate (propind), 2-benzoyl-1,3- indandionate (bind) or 2-(4-methyl)benzoyl-1,3-indandionate (mbind). These complexes were characterized by elemental analyses, Fourier-infrared absorption spectroscopy, thermogravimetric analyses. The bilayer electroluminescent devices were prepared with the following configuration ITO/NPB/[Al(aind)3]/LiF/Al, where NPB is N,N-bis-1-naphhyl-N,N -diphenyl-1,1-bifenil-4,4-diamina. The photoluminescent spectra of all complexes are characterized by overlapped broad bands arising from both fluorescence (around 640 nm) and phosphorescence (around 525 nm) phenomena (Fig. 1 (a)). On the other hand, their OLEDs exhibited only a high electroluminescence intense band in the red spectral region that may be assigned to the phosphorescence from acyl-1,3-indandionate ligands (Fig. 1 (b)). These data reflects the highest population of excited triplet state when the complexes are electrically excited. Furthermore, the OLEDs presented emission from low tension (~12V), reaching the highest intensity around 16 V. According with these results, the tris(2-Acyl-1,3- indandionate)aluminum(III) complexes act as both efficient electron transporters and emitting layers.