Synthesis Of Aromatic Ring Organic Small Molecules And Its Application In Organic Thin Film Transistors(OFETs)

In the 1980s,the scientific community first reported organic field-effect transistors(OFETs).OFETs have the advantages of a wide variety of organic semiconductor materials,wide sources,controllability,and low production costs.However,the film mobility of OFETs is far lower than that of inorganic field effect transistor.Organic semiconductor material is one of main factors affecting the performance of OFETs.In this paper designed and synthesized two small molecule systems containing aromatic ring structure,and they were used as semiconductor layers in OFETs.The research content of this paper is as follows:(1)In order to solve the problem of fewer types of organic semiconductor materials,and discussed differet self-assembled molecules and differet annealing temperature on the performance of devices.The specific experimental content of this system is as follows:first introduced oxygen-2-ethylhexyl and oxygen-n-octyl into the positions 5 and 6 of benzothiadiazole(BT),and synthesized two molecules with BT as the core groups,and then reacted with benzodithiophene(BDT)to form dialdehyde,D1 and D2 were synthesized by introducing cyano-n-octyl ester as a terminal group into the dialdehyde.Ultraviolet-visible spectroscopy(UV)analyzed the optical properties of materials,Thermogravimetric analysis(TGA)studyed the thermal stability of materials,and Cyclic voltammetry(CV)to calculated the Highest occupied molecular orbital(HOMO)and lowest occupied molecular orbital(LUMO).X-ray diffraction(XRD)and Differential scanning calorimetry(DSC)analyzed the crystallinity of two materials,and it was found that the film crystallinity and molecular order of D1 and D2 were good.Through the atomic force microscopy(AFM)analysis,the film quality is the best when the annealing temperature is 80°C.In device preparation,comparing the performance differences of transistors with different structure types,it is found that the bottom-gate top-contact type had the best performance.Comparing the device performance difference of different self-assembled molecules—Octadecyl phosphate(ODPA)and cetyl phosphoric acid(TDPA)modified substrates,and exploring the devices performance difference at different film annealing temperatures,and it was found that when the self-assembled molecules was ODPA,when the film annealing temperature was 80°C,the film quality of the organic semiconductor layer was improved,and the device based on D2 material had a higher mobility of 1.25×10^-2cm²v^-1s^-1.(2)In order to solve the problem of fewer types of n-type semiconductor materials and low device performance.This experiment designed and synthesized two systems of pyromellitic anhydride(BTDs)and tetrachl oroperylene imide(PBIs),at both ends of the central system of pyromellitic anhydride(BTD)and perylenetetracarboxylic anhydride(PBI)By introducing different R groups synthesized BTD-DBJ,BTD-ANI,BTD-PHR,PBI-DF,PBI-NH,PBI-HJ small molecule materials.TGA analyzed the thermal stability of these materials,and CV calculated the LOMO of these materials.The R group introduced in the BTDs series are electron donating groups,and the conjugated area of the system is very small,and devices based on these materials didn't show mobility.PBI introduces chlorine on both sides of the PDI,which causes the plane to be distorted,restricts the transmission of electrons,and devices based on these materials didn't exhibit good performance.