Schiff Base Zinc(II) Complexes as Promising Emitters for Blue Organic Light-Emitting Diodes

Abstract

Organometallic blue fluorescent Zn(II) Schiff base complexes are synthesized and explored computationally in order to use them in organic electroluminescent heterostructures. Characterization of these pyrazolone-based azomethine-zinc complexes was accomplished by various physicochemical techniques to get insight on their applicability as active layer in light-emitting diodes. All the complexes demonstrate high thermal stability and remarkable photoluminescence both in solution and in solid state with maximum in the blue region. Quantum chemical calculations of the first exited electronic state and vertical singlet-singlet electronic transitions by means of time dependent DFT calculations and results show that the origin of the luminescence for the target complexes refers to the intra-ligand charge transfer within the Schiff bases. The constructed light-emitting diodes demonstrate low input voltage (3.2-4.0 V), brightness at the level of 4300-11600 Cd m-2 and external quantum efficiency up to 3.2 % that is a good value for purely fluorescent OLEDs.