Synthesis And Properties Of Novel Orange-red Emissive Materials Based On Benzothiodiazole

In recent years, organic light emitting devices (OLEDs) have become a very popular flat-panel displaying technology. It is also an urgent need for better display performance products to meet the arrival of the information age. Compared with other conventional display and lighting technologies, organic light emitting devices have obvious advantages in flat panel display and solid-state lighting field. White OLED assemble with color filter has become important method for realizing full-color display, and received more and more attention. Currently in order to get highly efficient and stable white OLEDs, multi-emitting-layer structures are often exploited, in which two or more emission centers, corresponding to different colors, are physically separated from each other, such as the blue-orange light (two components) or RGB (three components). In comparison, the former is more prosperous due to its simple preparation, and longer life. For preparation of two-components white OLED devices, orange-red light emitting materials are indispensable in addition to the mature blue light-emitting material. Therefore, it is desired to develop novel orange-red luminescent materials to achieve full-color display and white lighting.Carbazole and its derivatives are a class of excellent hole transport materials, triphenylamine is good electron-donating materials that can provide steric hindrance to reduce the stacking of molecules, both of which are widely used in organic light emitting devices as excellent P-type groups. Benzothiadiazole and its derivatives are a class of strong fluorescent dyes and are widely used in organic electroluminescence and solar cells. In this thesis, seven novel benzothiazole-based luminescent molecules, namely BTZ-1to BTZ-7, have been designed and prepared by attaching carbazole, triphenylamine, fluorobenzene, and/or tetraphenylethylene at the4-and7-sites of BTZ, for potential application as emitters in OLEDs.Their photophysical properties, thermal properties and electrochemical properties have been studied by UV-Vis absorption and photoluminescence spectra, thermogravimetric analysis, cyclic voltammetry measurements. And density functional theory calculation was performed to understand this properties. The results show that most of these materials have good orange-red light emission, for example BTZ-1is red emissive with λmax at631nm. The thermal stability of four representative compounds were studied by means of thermal gravimetry analysis (TGA). Their thermal decomposition temperatures were observed to be at over400℃.Even more, for BTZ-4and BTZ-5with symmetrical structures, their thermal decomposition temperatures are above500℃. All compounds exhibit reversible reduction peaks in the negative potential region in CV measurements. Molecular orbital distribution is calculated by DFT. The HOMO and LUMO of BTZ-1, BTZ-2, BTZ-3are almost completely separated, whit HOMO mainly distributed on the electron rich triphenylamine group, and LUMO on the benzothiadiazole ring. This reduces the energy gap of triplet and singlet state, and benefits the inverse inter-molecular intersystem crossing, thus makes it possible to achieve thermally induced delayed fluorescence.