Structure Design And Properties Of Fluorinated Benzodifuranone Based Organic Semiconductor Materials

In the era of information explosion,the semiconductor industry plays a crucial role.In the whole development process,the most central is the semiconductor material.As the electronic materials used in the manufacturing process of semiconductor devices and integrated circuits,semiconductor materials form the foundation of the development of the entire semiconductor industry.Compared with inorganic semiconductor materials,organic semiconductor materials have the advantages of diverse molecular structures,easy regulation,lightweight and good flexibility,which has become an important research field in materials science.In its research and application,the development of n-type organic semiconductor materials lags behind obviously,and the material type and device performance are much lower than that of p-type organic semiconductor materials,which seriously affects the development of organic semiconductor.In this paper,we first review the factors affecting the properties of n-type organic semiconductor materials,summarize the influence of fluorination on the properties of organic semiconductor materials,select Benzodifurdione（BDF）molecules with stable electrochemical properties and low intrinsic conductivity,A series of new organic conjugate small molecules and polymers based on BDF were synthesized through fluorination modification,regulation of intramolecular/intermolecular non-covalent bond interaction and construction of strong Donor-Acceptor（D-A）structure.The molecular structure,crystalline properties,thermal properties,optical properties,electrochemical properties and device properties of field-effect transistors were analyzed and characterized.The main research contents and results are as follows:（1）The BDF,2F-BDF and 4F-BDF were designed and synthesized by introducing different number of fluorine atoms into the double terminal benzene ring of BDF molecule.Gaussian theoretical simulation and electrochemical test show that these three molecules can meet the energy level requirements of effective electron injection and stable electron transfer in n-type organic semiconductor materials,and the fluorinated molecules are more conducive to carrier excitation and electron transition.It was confirmed by XRD that the molecule had good crystallinity before and after fluoridation.TGA and DSC analysis results showed that the molecules before and after fluoridation had good thermal stability.The test results of thin-film field-effect transistors show that introducing fluorine atoms into the BDF end benzene ring is an effective way to transform p-type into n-type organic semiconductor materials.The electron mobility of 4F-BDF is as high as 2.69×10^-3cm²V^-1s^-1.（2）The f BDF and ff BDF were designed and synthesized by introducing different numbers of fluorine atoms into the central nuclear benzene ring structure of BDF molecule.The results of Gaussian theoretical simulation and electrochemical test show that the introduction of fluorine atoms can effectively reduce the lowest unoccupied molecular orbital（LUMO）energy level of the molecule,thus promoting the electron transfer and transport.It was confirmed by XRD that the molecule had good crystallinity before and after fluoridation.The test results of transistors confirm that the ff BDF exhibits n-type transport behavior,and it is confirmed that the introduction of fluorine atoms into the central nuclear benzene ring of BDF organic conjugated small molecules can effectively induce the transformation of organic semiconductor molecules from p-type to n-type transport characteristics.（3）Three kinds of BDF molecules with central fluorinated nuclei were used as electron accepters to obtain D-A type PBDF,Pf BDF and Pff BDF polymer molecules,respectively.Gaussian theoretical simulation and electrochemical test show that the introduction of difluorine atoms in the repetitive structure unit significantly reduces the LUMO energy level and band gap,which is more conducive to electron injection.It was confirmed by XRD that theπ-πpacking of polymer films was more compact after the introduction of fluorine atoms.The results of TGA and DSC analysis showed that the three polymers had good thermal stability.UV-visible spectra show that strong F-H interaction is formed in the molecule after fluoridation,and the higher the degree of fluoridation,the higher the degree of order of the film.The test results of transistors confirm that the molecular design strategy of fluorination not only helps to improve the carrier mobility of polymers,but also helps to realize the transformation of materials from single p-type to bipolar transport characteristics.Among them,the polymer Pff BDF molecule shows obvious carrier transfer characteristics of bipolar semiconductor,the maximum hole mobility is 1.17 cm²V^-1s^-1,the maximum electron mobility is 0.14 cm²V^-1s^-1.