Synthesis And Properties Of The Red Phosphorescent Materials Containing Oligomeric Siloxane Core

The tremendous interest in OLEDs and displays made from OLEDs is especially caused by technological aspects such as low costs, the ease of fabrication using standard techniques, the possibility of realizing flexible or large-area displays, their use in lighting applications. After decades of development, the OLED mobile phone, OLED lights, OLED-TV have gradually appeared. However, the current external quantum efficiency of the highest red phosphorescent materials was only 20.2 %, which is far behind the green and blue light-emitting materials. In order to reduce the concentration quenching phenomena caused by molecular stacking or aggregation, we introduced polyhedral oligosilsesquioxanes(POSS) into the red materials. POSS materials are the important organic/inorganic hybrid materials and usually possess high performances, which have not only the property of organic components, but also the property of inorganic silicon-based components. The POSS core is crucial to realize high performance materials with well-balanced property.The workes in this paper are supported by the National Natural Science Foundation of China. The main contents include:(1) Four new heteroleptic iridium complexs Ir(nbt)2(pic-Ox), Ir(nbt)2(pic-Cz), Ir(nbt)2(pic) and POSS-7Cz-Ir(nbt)2(pic)(POSS-pic) were synthesized and characterized by 1H NMR and MS, in which Ir(nbt)2(pic-Ox) contains an electron transport group and Ir(nbt)2(pic-Cz) has a hole transport group, and POSS-pic is a new organic/inorganic hybrid phosphorescent materials.(2) The photophysical properties of the new Ir(III) complexes were examined via ultraviolet-visible and photoluminescence spectroscopic spectra. The good thermal stability of the Ir(III) complexes were demonstrated by the thermogravimetric analysis, and Cyclic voltammetry(CV) was employed to investigate the electrochemical behavior of the Ir(III) complexes. The results showed that they all exhibit a strong red emission with a maximum main peak at 605 nm and a shoulder peak at 650 nm, which are typical red materials. The decomposition temperature of four materials were more than 280 ?.(3) In fabricating electroluminescent(EL) devices of the Ir(III) complexes, the complex Ir(nbt)2(pic) did not decompose via vacuum deposition, while the complexes Ir(nbt)2(pic-Cz) and Ir(nbt)2(pic-Ox) appeared decomposition obviously. Thus, the devices based on(nbt)2Ir(pic) with a device architecture of ITO/TAPC(20 nm)/CBP: Ir(nbt)2(pic)(30 nm)/TPBi(50 nm)/Liq(2 nm)/Al(150 nm) were fabricated by vacuum-deposition method. For the complexes Ir(nbt)2(pic-Cz) and Ir(nbt)2(pic-Ox), the multilayer OLEDs with a device architecture of ITO/PEDOT:PSS(30 nm)/CBP:Ir(III) complex(x wt%, 50 nm)/TPBi(50 nm)/Liq(2 nm)/Al(150 nm) were fabricated by solution-processable method. The EL performances of these three devices showed that the maximum luminance of them are more than 1000 cd/m2 and the current efficiencies is 3.8 cd/A, 3.5 cd/A and 3.25 cd/A, respectively.The purpose of this study is to synthesize new red phosphorescent materials to simplify the structure of the devices and to improve the development of red light-emitting materials.