Homologous Series of Phenylquinoline-Carbazole Main Ligand Based On Red-Emitting Iridium(III) Complexes for Phosphorescent Organic Light-Emitting Diodes

• Published in: Journal of physical chemistry. C Vol. 116; no. 13; pp. 7526 - 7533
• Main Authors: Song, Myungkwan, Park, Jin Su, Gal, Yeong-Soon, Kang, Sunwoo, Lee, Jin Yong, Lee, Jae Wook, Jin, Sung-Ho
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 05.04.2012
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electroluminescence; Electronics; Electrooptical effects; Exact sciences and technology; Materials science; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Optoelectronic devices; Other luminescence and radiative recombination; Other materials; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Specific materials; Interfacial layer; Interlayers; TDS; High density; Ligand; Electrooptical properties; Iridium complex; Organometallic compound; Theoretical study; Rolling; Electroluminescence; Quantum yield; Carbazole; Light emitting diode; Electrochemical properties; Organic light emitting diodes; Density functional method; Photoelectronic properties; Current density
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp2101094

New red-emitting phosphorescent Ir(III) complexes, bis[9-ethyl-2-(4-phenylquinolin-2-yl)-9H-carbazolato-N,C2′]iridium picolinate-N-oxide [(2-Et-CVz-PhQ)2Ir(pic-N-O)] and bis[9-ethyl-3-(4-phenylquinolin-2-yl)-9H-carbazolato-N,C2′]iridium picolinate-N-oxide (3-Et-CVz-PhQ)2Ir(pic-N-O), were synthesized, and their applications in phosphorescent organic light-emitting diodes (PhOLEDs) as well as their photophysical, electrochemical, and electroluminescent (EL) properties were investigated. To tune the performance of PhOLEDs containing these substances, the 9-ethyl-2-(4-phenylquinolin-2-yl)-9H-carbazole (2-Et-CVz-PhQ) and 9-ethyl-3-(4-phenylquinolin-2-yl)-9H-carbazole (3-Et-CVz-PhQ) were prepared and used as main ligands for the synthesis of Ir(III) complexes. The solution processed red PhOLEDs with a configuration of ITO/PEDOT:PSS/TCTA/PVK or 3-Et-CVz-PhQ:TPD:OXD-7:Ir complex/cathode were fabricated. The maximum EL emission peaks of (2-Et-CVz-PhQ)2Ir(pic-N-O) and (3-Et-CVz-PhQ)2Ir(pic-N-O) were observed at 689 and 609 nm, respectively. The PhOLEDs with (2-Et-CVz-PhQ)2Ir(pic-N-O) and (3-Et-CVz-PhQ)2Ir(pic-N-O) exhibited respective maximum external quantum efficiencies of 4.32% and 8.74% along with CIE (Commission International de l’Eclairage) coordinates of (0.68, 0.28) and (0.62, 0.37), respectively. Furthermore, by introducing a TCTA interlayer, the PhOLEDs showed a slight efficiency roll off of 15% from a low current density (1 mA/cm2) to a high current density (30 mA/cm2). The electro-optical properties and the performance of PhOLEDs, prepared by using the two Ir(III) complexes, were probed through the use of density functional theory (DFT) calculations.