High performance Europium(III) based emitters for electroluminescence: Synthesis, crystal structures, photophysical and electroluminescent properties

In this paper, we synthesize two 1,10-phenanline derived ligands, along with their corresponding Eu(III) complexes. Their crystal structures, photophysical characteristics, including UV–vis absorption, photoluminescence (PL), quantum yields, excited state lifetimes, and thermal stability, are discussed in detail. In addition, we also investigate their potential application in electroluminescence (EL) devices. Experimental data suggest that the two Eu(III) complexes are promising emitters for EL application: pure red emissions with a maximum EL brightness of 850 cd/m2 and a maximum current efficiency of 3.67 cd/A are achieved. It is found that the elimination of active hydrogen in ligand favors most PL and EL factors, including PL quantum efficiency, thermal stability, and current efficiency, but not for maximum EL brightness. An emitter with shorter excited state lifetime leads to a higher EL brightness, regardless of its relatively lower device efficiency.