Synthesis and characterisation of soluble aluminium complex dyes based on 5-substituted-8-hydroxyquinoline derivatives for OLED applications

Abstract

Some new 5-substituted 8-hydroxyquinoline derivatives and their Al(III) complex dyes (Al(2)₃–Al(9)₃) have been synthesised. The compounds were characterized by ¹H, ¹³C, mass and elemental analysis. The aluminium complexes retain the spectroscopic properties of the parent compound, namely, tris(8-hydroxyquinolinato) aluminium (III) (AlQ₃). In dichloromethane solution, these aluminium complexes show absorption maxima in the range of 390–395 nm, strong green luminescence in the range 527-536 nm and aluminium complexes show high fluorescence quantum yield in solution and thin films. The fluorescence decay in solution as well as in thin film is fitted to biexponential with τ_av ranging from 3 to 9 ns. Electroluminescence (EL) of the spin-cast film of Al(3)₃ (3=5-(2-ethylhexyloxymethyl)-8-hydroxyquinoline) as the emitting layer was performed and the turn-on voltage for the EL device is about 11 V.