Design And Synthesis Of Fused Heterocyclic Small Molecules And Isoindigo-based Polymers And Its Device Properties

The organic field-effect transistor?OFET?has a very broad application prospect in realizing light weight,low-cost,solution processing,large-area preparation and flexible devices such as radio frequency identification tag,electronic paper and flexible display,etc.Designed and synthesized of organic semiconductor materials with excellent comprehensive performance,carrier transport mechanism and corresponding structure-property relationship of organic semiconductor materials in transistor devices are two major scientific problems in the field of organic field-effect transistors.Difficulties such as the lack of high-performance organic semiconductor materials and the carrier transport mechanism are not clear,etc.Therefore,this paper designs and synthesizes a series of fused-ring organic small molecules and isoindigo-based polymers and studies its physicochemical properties and OFETs device performance.The main research contents are as follows:1.Designed and synthesized D-A type five-membered fused heterocyclic small molecule IC-DDTPTI and IDC-DDTPTI,and studied the effects of different degrees of electron-withdrawing acceptor units?A?on the UV-vis absorption spectra,electrochemical and OFET device properties of materials.The experimental results show that transistor device with IC-DDTPTI as semiconductor material exhibits balanced ambipolar charge transfer behavior,the highest electron mobility is 0.40cm²V^-1s^-1,and the maximum hole mobility is 0.18 cm²V^-1s^-1.The organic semiconductor material IDC-DDTPTI which contain a stronger electron-withdrawing acceptor unit?IDC?,has a lower LUMO level?<–4.0 eV?,correspondingly the transistor device exhibits a unipolar n-type charge transfer characteristics and the molecule has very good solubility!This will develop a new receptor unit for design and synthesis of D-A type high performance organic semiconductor molecules,which conducive to the rapid development of new D-A structure high performance semiconductor materials in the OFET field.2.The A₁-D-A₂-D conjugated polymers PIIDDTBT and PIIDDTffBT based on isoindigo structure were designed and synthesized.The effects of fluorine atom substituents on the UV-vis absorption spectrum,electrochemistry and OFET device performance of the system were studied in detail..The experimental results show that the transistor device based on conjugated polymer PIIDDTBT without fluorine atom substituents exhibits ambipolar charge transfer behavior(electron/hole mobility is10^-2/10^-3 cm²V^-1s^-1,respectively).The introduction of fluorine atom substituent further reduces LUMO levels of the compound PIIDDTffBT and forms F…S conformational lock on the polymer conjugated backbone,so that the polymer molecular arrangement is more orderly and regularly,thereby causing its corresponding transistor device to exhibit excellent performance and balanced ambipolar charge transfer characteristics(highest hole/electron mobility exceeds 0.1 cm²V^-1s^-1)!This work has further confirmed that the introduction of fluorine atom substituents has a very important influence on the charge transport characteristics of isoindigo-based polymers.3.An octagonal fused-ring molecular Q2P3TT based on bithiophene-pyrrole structure was designed and synthesized,which was characterized by UV-vis absorption spectroscopy,infrared spectroscopy,Raman spectroscopy,nuclear magnetic resonance spectroscopy,mass spectrometry,EPR,SQUID and DFT theoretical calculation.A series of characterization confirm that the molecule has typical stable diradical properties.4.Five compounds Br-DPE,Br-BMTPE,Cl-BMTPE,I-BMTPE and Br*-BMTPE were synthesized by introducing an electron-donating group methylthio group on the trans-stilbene skeleton and changing the type and position of the halogen substituent,and UV-vis absorption spectroscopy,fluorescence emission spectrum and single crystal structure of the series of compounds were characterized.The effects of electron-donating groups,halogen substituent types and positions on the halogen-halogen interaction in the aggregated state were systematically investigated.The experimental results show that the compounds Br-BMTPE,Cl-BMTPE and I-BMTPE form a strong halogen-halogen interaction.The absence of halogen-halogen interactions in the compounds Br-DPE and Br*-BMTPE further confirms that the electron-donating group,types and positions of the halogen substituent are critical for the formation of halogen-halogen interactions.In addition,the halogen-halogen interaction compounds Br-BMTPE and Cl-BMTPE have strong?-?interaction,but still exhibit strong fluorescence characteristics,which is a new design and synthesis of functional materials with both conductive and luminescent properties.