High-performance white light-emitting diodes based on an efficient trivalent europium molecular complex

Abstract

Trivalent europium-based monochromatic red emissive phosphors are necessary constituents for high-performance solid-state lighting (SSL) devices. Here, in the present study, we report the efficient molecular Eu(III) based red-emitting complexes Eu(TTA)₃-TPA-DPA-Ph/t-butyl based on two phenanthroimidazole derivatives, TPA-DPA-Ph/TPA-DPA-t-butyl, as an ancillary ligand. Both ligands show green emission in the solid state and solution. In contrast, Eu complexes show vivid red emission under excitation at ∼345 nm (in the solid state, solution, and thin film). The synthesized complexes produce a narrow emissive band with pure red emission (FWHM ∼6 nm), which is highly chromatically rich to the human eye and leads to excellent chromatic color saturation of the red spectral window. Significant efforts have been devoted to understanding the principle of energy transmission mechanisms theoretically and experimentally. Highly bright red color emissive light-emitting diodes (LEDs) were created by coupling the red Eu(III) complexes as a red phosphor with a near-UV (NUV) LED chip (395 nm) operated at a 20 mA forward bias. In addition, hybrid white LEDs (WLEDs) were created using Eu(TTA)-TPA-DPA-Ph as the red component and TPA-DPA-Ph as the green component. The two-component mixed white LED spectrum demonstrates pure white light emission with a low CCT (4499 K), a high CRI (87), and CIE values of x = 0.33; y = 0.36. All the synthesized red phosphors are found to be excellent for SSL applications. The spectrum of a WLED using a mixture of yellow dye was obtained, and the Eu complex showed pure white light emission with a low CCT (3704 K), high CRI (93), and CIE values of x = 0.33; y = 0.33.