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 ZnQ₂, CaQ₂, and CdQ₂ 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 °C had high thermal stability. The ZnQ₂ complex has also a maximum temperature in 527 °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 ZnQ₂, CaQ₂, and CdQ₂ bonds were determined. The maximum green photoluminescence at 565, 523, and 544 nm were observed from ZnQ₂, CaQ₂, and CdQ₂ powders, respectively. Comparing fluorescence data results showed that the intensity fluorescence of ZnQ₂ and CdQ₂ was reduced in comparison with the fluorescence of CaQ₂. The optical, thermal and electrical properties of ZnQ₂, CaQ₂, and CdQ₂ powders were evaluated for possible application in organic light emitting devices.