Photo-and electroluminescent properties of mixed ligand zinc complexes for organic electroluminescent device applications

Two Schiff base mixed ligand 4-[(N(2-hydroxy-1-naphthalidene)amino)antipyrine]zinc and 1,10 phenanthroline mixed ligand Schiff base zinc complexes were synthesized and characterized using 1H and 13C NMR, mass spectroscopy, elemental analysis, IR and UV-vis spectra. The thermal stability of compounds was characterized by TGA and its glass transition temperature was determined by the DSC method. Photoluminescence spectra show the emission peaks of both complexes lie in the 450-550 nm blue-green region. These two zinc complexes were used as a dopant material for mixed host materials with a concentration of 8 %. A series of devices having mixed host materials (mCPx:TPBI1-x) with the concentration of x = 0,1/4,1/2 and 3/4 have been developed. The concentration of both host materials was equal. The maximum luminance, current and power efficiency of the devices with zinc complex Zn(L) can reach up to 5516 cd/m2, 4.4 cd/A and 3.52 lm/W which are improved by introducing phenanthroline mixed ligand in the zinc complex Zn(phen). These results show that by changing the concentration of host material and introducing mixed ligand in the zinc complex can broaden the recombination zone and also balance the charge carrier in the emissive layer.