Synthesis and characterization of greenish-blue light emitting lithium-boron complex for organic light emitting diode applications

A lithium-boron complex, lithium tetra (2-methyl 8-hydroxy quinolinato) boron (LiBqm4), which emits greenish-blue light has been synthesized by the reaction of LiBH4 with 2-methyl 8-hydroxyquinoline in a molecular weight ratio of 1:4, and used for organic light emitting diodes (OLEDs) fabrication. The complex has been characterized by optical absorption, Fourier Transform Infrared (FTIR), photoluminescence (PL) and electroluminescence (EL) spectroscopic methods. The thermo-gravimetric analysis (TGA) suggests that the material is quite thermally stable up to 380C. An optical band gap of 3.15 eV using the well-known Tauc relation and an exciton binding energy of 0.69 eV has been evaluated. OLEDs have been fabricated in ITO/N,N′-di-(3-methyl-phenyl)-N,N′diphenyl-4,4′diaminobiphenyl(TPD)/LiBqm4/Al configuration. PL and EL peaks exist at 503 nm. I-V characteristic of device reveals that at higher voltages the current follows I ∝ V law, where m > 1.