Study On The Synthesis Of Naphthalene Diimide Conjugated Polymers And The Performance Of Field-effect Transistors

Conjugated donor-acceptor?D-A?copolymers have become an ideal class of high-performance semiconductor materials for organic field effect transistors.Due to its unique solution processability,diverse molecular design and easily regulated energy levels,conjugated polymers have attracted wide attention in light,low-cost and large area flexible electronic products?such as field-effect transistors?OFETs??.The development of n?electron transport?-type organic semiconductors is far behind that of p?hole transport?-type semiconductors.Naphthalene diimide?NDI?group,due to its high coplanarity,easy to be modified and convenient for conjugated structure,has become a common building unit for the design and synthesis of n-type organic semiconductor materials,and NDI polymers are easy to be synthesized,with good solubility and crystallinity,and synthesizing polymers with different donors can regulate the energy level of the molecule and achieve different transmission types.This thesis designed and synthesized several polymers with NDI as acceptor units,and characterized their thermal stability,optical performance,electrochemical performance,field effect performance,etc.The main contents and experimental results are as follows:A conjugated polymer based on naphthalene-diimide and dithiophene units was synthesized by continuous flow synthesis.Due to the large specific surface area and excellent heat transfer,the polymerization was completed within?35 min at 110^oC.Compared to flask synthesis,the continuous flow technology exhibited a high synthesis effiffifficiency and significant reduction in reaction times.The polymer using flow synthesis exhibited higher molecular weight,lower polydispersity indexes,and a more ordered crystalline structure.Consequently,much higher electron mobilities 0.77cm²V^-1s^-1with I_on/I_offratios of 10⁶were obtained for the polymer using flow synthesis.Four different NDI-based conjugated polymers were synthesized by introducing different numbers?0,1,2,4?of electronegative nitrogen atoms on the donor unit.The HOMO energy level is reduced from-5.76 e V to below-5.90 e V,which is conducive to blocking hole injection into the semiconductor layer.In addition,the oxidation resistance of the material can be improved so as to enhance its stability.Under vacuum,all polymer devices exhibit pure n-type electron transport,with NDI-TTz T having the highest mobility and the maximum electron mobility of 0.073 cm²V^-1s^-1.The devices NDI-TPh T and NDI-TPd T show bipolar transmission in air,while NDI-TPa T and NDI-TTz T show pure n-type electron transmission in air.The microstructure of these polymer films was studied and found that NDI-TTz T has the shortest?-?stacking distance of 3.79?,which effectively prevents water and oxygen from entering the film to capture electron carriers,which can improve device performance.