Green-white electroluminescence and green photoluminescence of zinc complexes

A series of zinc complexes has been synthesized and utilized as fluorescent materials in organic light-emitting diodes (OLEDs). All prepared complexes were characterized by elemental analysis (CHN), UV-vis, FT-IR and 1H NMR spectroscopy. The energy levels of zinc complexes were determined by cyclic voltammetry measurements. Devices with fundamental structure of ITO/PVK:PBD (50 nm)/zinc complexes/BCP (5 nm)/Alq3 (25 nm)/Al (180 nm) were fabricated. A green electroluminescence was obtained from thin film complexes at 25 nm thickness. When thickness of the complex bis(2-methylquinolin-8-olato)-bis[(acetato)-(methanol)zinc(II)] (B) in thin film decreased from 25 nm to 20, 18, and 12 nm, a white electroluminescence obtained. The white emission which was composed of blue and green attributed to the PVK:PBD blend and thickness of complex, respectively. With 12 nm thickness of complex, a maximum luminance of 4530 cd/m2 at a current density 398.32 mA/cm2 with CIE coordinates of 0.22 and 0.36 at 20 V was achieved.