Tuning colors in novel electroluminescent devices based on Al-indandionate complexes

Abstract

In the past years, the development of materials for organic light-emitting diodes (OLEDs) have attracted much attentions [1]. In this sense, the present work reports about syntheses, characterization, Photo (PL) - and electroluminescence (EL) properties of Al-indandionate complexes of formula [Al(aind)3], where aind: 2-acetyl-1,3-indandionate (acind), 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 and 1H-NMR. Photoluminescent spectra of the complexes in both powder and thin film exhibited overlapped broad bands associated to both fluorescence and phosphorescence (see time-resolved spectra, Fig. 1a) phenomena. The electroluminescent devices of configuration ITO/β-NPB/Al(aind)3/LiF/Al (1) exhibited emission in the red spectral region associated to electrophosphorescence (figure 1.b). On the other hand, the three layers devices of configuration ITO/β-NPB/spiro-2CBP/Al(aind)3/Al (2) showed an intensity band in green spectral region (figure 1.b). The OLEDs presented emission from low voltage (~8V), reaching the highest intensity around 16 V. According to these results, the Al-indandionate complexes act as both efficient electron transporters and emitting layers. In addition, these data suggest that TADF process is operative in the bilayer devices.