title: Pyrimidine-Based Mononuclear and Dinuclear Iridium(III) Complexes for High Performance Organic Light-Emitting Diodes.
abstract: Containing two nitrogen atoms, the electron-deficient pyrimidine ring has excellent coordinating capability with transition metal ions. However, compared with the widely used pyridine ring, applications of the pyrimidine ring in phosphorescent Ir(III) complexes are rare. In this research, two highly emissive pyrimidine-based mononuclear Ir(III) complexes and their corresponding dinuclear Ir(III) complexes were prepared with a simple one-pot reaction. The incorporation of the second Ir(III) center can lead to dramatic differences of both photophysical and electrochemical properties between the mono- and dinuclear complexes. Besides, these properties can also be fine-tuned with different substituents. Theoretical calculations have also been performed to understand their photophysical behaviors. The electroluminescent investigations demonstrate that the pyrimidine-based mono- and dinuclear Ir(III) complexes could show impressive device performance. The vacuum-deposited organic light-emitting diode (OLED) based on the mononuclear Ir(III) complex exhibited an external quantum efficiency (EQE) of 16.1% with almost no efficiency roll-off even at 10 000 cd m-2. More encouragingly, the solution-processed OLED based on the dinuclear Ir(III) complex achieved the outstanding EQE, current efficiency (CE), and power efficiency (PE) of 17.9%, 52.5 cd A-1, and 51.2 lm W-1, respectively, representing the highest efficiencies ever achieved by OLEDs based on dinuclear Ir(III) complexes.
authors.affiliation: MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Institute of Chemistry for New Energy Materials, Department of Chemistry, School of Science, Xi'an Jiaotong University , Xi'an 710049, People's Republic of China.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Yang
authors.affiliation: MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Institute of Chemistry for New Energy Materials, Department of Chemistry, School of Science, Xi'an Jiaotong University , Xi'an 710049, People's Republic of China.
authors.forename: Zhao
authors.initials: Z
authors.lastname: Feng
authors.affiliation: MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Institute of Chemistry for New Energy Materials, Department of Chemistry, School of Science, Xi'an Jiaotong University , Xi'an 710049, People's Republic of China.
authors.forename: Jiang
authors.initials: J
authors.lastname: Zhao
authors.affiliation: MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Institute of Chemistry for New Energy Materials, Department of Chemistry, School of Science, Xi'an Jiaotong University , Xi'an 710049, People's Republic of China.
authors.forename: Jing-Shuang
authors.initials: JS
authors.lastname: Dang
authors.affiliation: MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Institute of Chemistry for New Energy Materials, Department of Chemistry, School of Science, Xi'an Jiaotong University , Xi'an 710049, People's Republic of China.
authors.forename: Boao
authors.initials: B
authors.lastname: Liu
authors.affiliation: MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Institute of Chemistry for New Energy Materials, Department of Chemistry, School of Science, Xi'an Jiaotong University , Xi'an 710049, People's Republic of China.
authors.forename: Kaini
authors.initials: K
authors.lastname: Zhang
authors.affiliation: MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Institute of Chemistry for New Energy Materials, Department of Chemistry, School of Science, Xi'an Jiaotong University , Xi'an 710049, People's Republic of China.
authors.forename: Guijiang
authors.initials: G
authors.lastname: Zhou
keywords: dinuclear iridium(III) complex; mononuclear iridium(III) complex; organic light-emitting diode; phosphorescence; pyrimidine