Synthesis And Field Effect Transistor Performance Of Bis(2-oxo-7-azaindolin-3-ylidene)benzodifuran-dione-based Conjugated Polymers

In recent years,solution processed conjugated polymers have attracted considerable research attention due to their high application value in light-weight?low-cost,and large-area flexible electronic devices.Among such polymer-based devices,organic field effect transistors(OFETs)are of special interest as building blocks for circuits,and for use in activematrix displays,non-volatile memory devices.Numerous conjugated polymer semiconductors have been developed for improving device performances.Among these polymers,the p-type semiconductors have made breakthrough progress,whereas the development of n-type semiconductors lags behind.The n-type semiconductor is an important part of constructing the complementary transistor logic circuit.So it is necessary to study stable n-type semiconductor.In order to obtain high-performance n-type polymer semiconductors,the current research is committed to building novel electron-deficient acceptor units.In this paper,we design a new electron-deficient unit,(3E,7E)-3?7-bis(6-bromo-1-(4-decyltetradecyl)-2-oxo-7-azaindolin-3-ylidene)benzo[1?2-b:4?5-b']difuran-2.6(3H,7H)-dione(BABDF)by replacing the outer benzene rings of bis(2-oxoindolin-3-ylidene)-benzodifuran-dione(BIBDF)with pyridine rings.Three novel n-type donor-acceptor(D-A)conjugated polymers,PBABDF-DT,PBABDF-TVT and PBABDF-nonTVT were synthesized based on this unit,and their thermal properties,photophysical,electrochemical property,field-effect properties and microstructural were also studied.The main research is as follows:(1)In chapter 2,Two donor-acceptor(D-A)conjugated polymers,PBABDF-DT and PBABDF-TVT,were synthesized using the strongly electron-deficient unit,BABDF as the acceptor,and dithiophene(DT)and(E)-2-(2-(thiophen-2-yl)vinyl)thiophene(TVT)as the donor units.Both polymers exhibited low LUMO energy levels(?-4.0 eV)for marching with electron transport.The organic field-effect transistors exhibited the highest electron mobilities of 1.86 cm2 V-1 s-1 and 1.56 cm2 V-1 s-1 with high Ion/Ioff ratios of 1.6 × 106 and 1.0 × 106 for PBABDF-DT and PBABDF-TVT,respectively.Both materials had highly uniform polymer nanofibers,orderly lamellar crystalline structures,and close ?-? stacking distances which all contributed to the high charge carrier mobility.(2)In chapter 3,In order to achieve higher electron mobility,we chose the PBABDF-TVT with smaller ?-? stacking distance to study the effect of alkyl chain removal on the basis of the second chapter.Removing the dodecyl chain on donor unit(E)-2-(2-(thiophen-2-yl)vinyl)thiophene,and a donor-acceptor(D-A)conjugated polymer PBABDF-nonTVT was synthesized using the BABDF as the acceptor,and non-alkyl chain(E)-2-(2-(thiophen-2-yl)vinyl)thiophene(nonTVT)as the donor unit.According to the simulation result of B3LYP/6-31G(d),the torsion angle of PBABDF-nonTVT backbone is 0.01°,which is significantly smaller than 9.4° of PBABDF-TVT,which shows that the coplanity of the polymer backbone is obviously improved.The polymer also exhibited low LUMO energy levels(?4.0 eV)for marching with electron transport.The organic field-effect transistor exhibited the electron mobility of 2.42 cm2 V-1 s-1 with Ion/Ioff ratios of 2.4×104 for PBABDF-nonTVT.The mobility of 2.42 cm2V-1s-1 is higher than that of PBABDF-DT and PBABDF-TVT in chapter 2.This is because the more highly uniform polymer nanofibers,more orderly lamellar crystalline structures,and closer ?-? stacking distances of the polymer which caused by the smaller torsion angle of the polymer backbone.All of these can help to further increase the electron mobility.