Synthesis And Characterization Of Pyrene-Diimide-Based Novel N-Type Organic Semiconductors

Organic semiconductors have become a central issue in academic research along with the development of organic electronics.Compared with the traditional inorganic semiconductors,organic materials have the advantages of easy modification,compatiblility with flexible substrate and large-area fabrication,and they have potential applications in flexible displays,electronic skins and various sensors.However,organic semiconductors also suffer some problems,such as low charge mobility and poor stability,which inhibit their applications in organic electronics.Therefore developing high performance organic semiconductors is greatly important.In this thesis,we designed and synthesized a series of organic semiconductor matrials based on pyrene,which is an electron-rich conjugated skeleton with good luminescent properties.Based on these novel materials,we have fabricated OFET and nonvolatile OFET memory devices.Devices exhibiting good performance were obtained after the optimization of molecular packing,dipolemoment and frontier orbital energy levels.We have investigated the structural-property relationship via theoretical calculations and provided new guidance for design of high performance n-type organic semiconductors.The main content of this thesis are listed below:Chapter one:The basic knowledge of organic electronics,organic field effect transistors,organic semiconductors and nonvolatile organic field effect transistors are introduced.The recent developments of organic semiconductors,structure and working principle of OFETs and nonvolatile OFET memory devices are reviewed.At last,the motivation of the research is introduced.Chapter two:The reagents and instruments used for synthesis,photo-electronic property characterization of organic materials are introduced.The equipments for the fabrication of OFET and nonvolatile OFET memory devices are illustrated.The working principle and the operation of some instruments are discussed.Chapter three:Design and synthesis of high performance n-type organic semiconductors are important for the development of future organic optoelectronics.Herein,we report the facile synthetic routes to reach the K-region of pyrene and obtain 4,5,9,10-pyrene diimide?PyDI?derivatives.The PyDI derivatives exhibited efficient electron transport properties with the highest electron mobility up to 3.08 cm²V^-1s^-1.Besides,the tert-butyl substituted compounds?t-PyDI?also showed good one and two photon excited fluorescence properties.The PyDI derivatives are new family of aromatic diimides that may exhibit both high electron mobility and good light emitting properties,making them excellent candidates for future optoelectronics.Chapter four:The molecule t-C₆-PyDI was chosen as the model system.We optimized the crystal packing by co-crystal method,and the electron transfer performance was thus improved.By single crystal analysis,UV-vis spectra,etc.we investigated the crystal packing and intermolecular charge transfer behavior in the co-crystal.We also analyzed the benefit of co-crystal method in promoting the charge transfer performance.Chapter five:We developed a new strategy to substitute on the K-region of pyrene and obtained a series of asymmetric pyreneimide derivatives with pyrazine substituents.We fabricated the nonvolatile OFET memory devices based on these molecules which exhibited good memory performance with high memory windows and stability.We investigated the influence of dipolemoment and frontier orbital energy level on the memory performance via the experimental characterization and theoretical calculation.