Novel green-emitting copper(I) complexes with electron donors incorporated ligands: Synthesis, photophysical properties, and electroluminescence performances

In this paper, we explore a diimine ligand of 2-thiazol-4-yl-1H-benzoimidazole (TB) with strong electron donors in its molecule. In addition, an excess electron-donor moiety of carbazole is incorporated through an inert alkyl chain to form another diimine ligand of 1-(4-carbazolylbutyl)-2-thiazol-4-yl-1H-benzoimidazole (CTB). Their corresponding Cu(I) complexes are synthesized as well. Experimental data confirm that both the Cu(I) complexes are high-energy-emitting ones. What is more, it is found that the emitter's photoluminescent and thermal performances can be greatly improved when active hydrogen is eliminated. Using the CTB-based Cu(I) complex as a dopant, we realize green-emitting devices with a maximum brightness of 1500 cd/m2 peaking at 525 nm, and the device efficiency roll-off in these devices is largely depressed due to the shield provided by carbazole moiety.