Synthesis of ZnQ2, CaQ2, and CdQ2 for application in OLED: optical, thermal, and electrical characterizations

In this study, zinc, calcium and cadmium based organometallic complexes were synthesized as fluorescent materials for the application in organic light-emitting diodes (OLEDs). The crystal structure of ZnQ(2), CaQ(2), and CdQ(2) complexes was determined applying X-ray diffraction. The synthesized complexes were characterized using visible and ultraviolet (UV-Vis), Fourier transform infrared (FT-IR), thermal gravimetric analysis (TGA), and photoluminescence (PL) spectroscopy analysis. The energy levels of Zn, Ca, and Cd complexes were determined by cyclic voltammetry measurements. Heat-treatment was carried out under nitrogen atmosphere at the temperature determined by thermo-gravimetric analysis. TGA results indicated that the complexes with initial decomposition temperatures more than 260 degrees C had high thermal stability. The ZnQ(2) complex has also a maximum temperature in 527 degrees C with M-res= 55% which is the highest values among three complexes. Further structural elucidation was carried out using FT-IR in which the stretching frequencies of ZnQ(2), CaQ(2), and CdQ(2) bonds were determined. The maximum green photoluminescence at 565, 523, and 544 nm were observed from ZnQ(2), CaQ(2), and CdQ(2) powders, respectively. Comparing fluorescence data results showed that the intensity fluorescence of ZnQ(2) and CdQ(2) was reduced in comparison with the fluorescence of CaQ(2). The optical, thermal and electrical properties of ZnQ(2), CaQ(2), and CdQ(2) powders were evaluated for possible application in organic light emitting devices.