Self-assembly Of Polymer Semiconductor Nanofibers And Their Applications In Organic Field-effect Transistors

Field-effect transistors(FETs)are a kind of devices which can directly indicate the carrier mobility by electric field effect.Compared with traditional inorganic field-effect transistors(IOFETs),organic field-effect transistors(OFETs)have the advantages of being prepared on flexible substrates,applicable to large-area processingand simple processing technology,low manufacturing cost and so on.It has great application prospects in the printing of large-area electronic circuits and flexible electronic equipments.The organic semiconductor layer is an important component of the fieldeffect transistor,and the polymer semiconductor has attracted a lot of research interest because it can be prepared on flexible substrates.Poly(3-hexyl thiophene)(P3HT)is a p-type organic semiconductor material widely used in field-effect transistors.In this paper,the synthesis method of P3 HT nanofibers is systematically studied by taking P3 HT nanofibers as an example,and the corresponding field-effect transistor devices are prepared by using P3 HT nanofibers as the organic semiconductor layer.The specific work is as follows:1.Preparation of P3 HT nanofibers by heating-cooling methodIn this work,P3 HT nanofibers were prepared by heating-cooling method and the tapping mode test of atomic force microscope(AFM)was mainly used to analyze their morphology.Based on the chlorobenzene(CB)solvent system,the effects of poor solvents,the ultrasonic treatment,molecular weights,and concentrations on the microscopic morphology of P3 HT were studied.Two synthetic methods with different P3 HT concentrations and different solvent ratios were summarized: 0.5 mg/m L P3 HT in CB: acetonitrile =5:1 and 3.0 mg/m L P3 HT in CB: acetonitrile =10:1,where the 0.5mg/m L system can maintain the nanofiber morphology for up to half a year.2.Preparation of top-gate field effect transistors based on P3 HT nanofibersTraditional organic field-effect devices usually adopt a bottom-gate device structure because the organic semiconductor layer is not resistant to high temperatures.However,owing to the interface of the OFET insulating layer of the bottom-gate structure is usually modified with octamethyltrichlorosilane(OTS)to reduce surface defectdensities,and subsequently the interface hydrophobicity after OTS modification is too strong,the P3 HT nanofiber solution prepared in the previous procedure can not be spin-coated on the surface of OTS-modified insulating layers.Therefore,using the top-gate structure and the P3 HT nanofibers prepared in the previous processing procedure,this work successfully fabricated organic field-effect transistors based on P3 HT nanofibers.Top-gate OFETs with short channels(L<2 μm)based on P3 HT nanofibers exhibits excellent electric performances,and are expected to be applied to low-voltage and short-channel devices.