Synthesis, Characterization and Luminescent Properties of Mixed-Ligand Nickel Complexes for Opto-Electronic Application

This paper reports the synthesis of a mixed ligand nickel complexes as an emissive layer in organic light emitting diode applications. Synthesized ligand and nickel complexes were characterized by Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance spectroscopy, mass spectroscopy, x-ray powder diffraction and scanning electron microscopy. This compound shows good thermal stability and film forming properties. Optical properties have been studied by UV–vis and photoluminescence (PL). Frontier molecular orbital theory energy levels of these compounds were demonstrated using density functional theory calculations. Photoluminescence (PL) emission peaks of complexes (1) and (2) show at 596 nm and 581 nm in solid state, respectively. The structure of the fabricated multi-layered device is: ITO/αNPD(300 Å)/(1)(350 Å)/BCP(60 Å)/Alq₃(280 Å)/LiF(10 Å)Al(1500 Å) and ITO/αNPD(300 Å)/(2)(350 Å)/BCP(60 Å)/Alq₃(280 Å)/LiF(10 Å)Al(1500 Å). Electroluminescence emission of devices (1) and (2) containing nickel complexes as the emissive layer emit at 568 nm and 561 nm, respectively. Commission Internationale de l’Eclairage chromaticity colour coordinates of devices (1) and (2) were found to be x = 0.426, y = 0.425 and x = 0.473, y = 0.447, respectively, which emits an orange colour. These results show that these nickel complexes can act as a promising emissive layer in opto-electronic applications as strong electroluminescent materials.