Deep Red Emission from Iridium Complexes for the Versatile Organic Light-Emitting Diodes

Abstract

A new phosphorescent iridium (Ir) complex, Ir(TMP-TT)(2)(acac) was synthesized for red emitter of the organic light-emitting diodes (OLEDs). The TMP-TT (2-(dithieno[3,2-b:2',3'-d]thiophen-2-yl)-4-(trifluoromethyl)-pyridine) has an electron conducting ability as well as the electron rich characteristics due to the sulfur atoms located on the fused thiophene rings. The ligand was synthesized by Suzuki coupling reaction. The Ir(TMP-TT)(2)(acac) was synthesized by Nonoyama reaction. The UV-visible absorption spectrum of Ir(TMP-TT)(2)(acac) showed peaks and shoulders at 366, 420, and 490 nm. The photoluminescence (PL) emission spectra showed blue light-emission at 440 nm with excitation at 366 nm and red light-emission peak at 638 nm with excitation at 490 nm in the chloroform. Optoelectronic properties of device with the structure of ITO/PEDOT (40 nm)/TFB (30 nm)/RH-02: Ir(TMP-TT)(2)(acac) (30 nm: 10%)/Bphen (40 nm)/Liq/Al were measured. The relative intensity of the dual wavelength emissions observed at 540 nm and 638 nm varied with applying voltage. The Ir complex will be used as a solution process dopant for the hybrid OLED devices.