Design,Synthesis And Propertiesof Semiconductors Based On Azafluoren

There are a wide range of applications for organic field effect transistors(OFETs)in radio frequency identification,flexible displays,sensors,etc.,and thus have received extensive attention in the academic community.Organic semiconductor materials are the basis of OFTSs.The properties of materials directly determine the application of OFETs.Therefore,designing and synthesizing high performance organic semiconductor materials is of great significance.A series of stable,high-performance p-type semiconductor materials have been synthesized,but the development of n-type semiconductor materials lags far behind p-type materials,which is an indispensable part of the circuit.In this paper,a pyridine ring was introduced into the molecular skeleton,and a series of n-type semiconductor materials were designed and synthesized by utilizing the electron-deficient properties of pyridine.At the same time,the band gap and mobility of the material are regulated by coordination of pyridine and metal.This paper mainly includes the following contents:1)Two kinds of thieno[3,4-c]pyrrole-4,6-dione(TPD)derivatives TPD-2-Py and TPD-4-Py terminated by 2-and 4-position pyridine were designed and synthesized.Nuclear magnetic resonance spectra,absorption spectra and emission spectra confirmed that they can be complexed by a nitrogen atom on the pyridine ring and a Lewis acid tris(pentafluorophenyl)borane(BCF).The absorption spectra show that TPD-2-Py and TPD-4-Py have similar absorption,but after complexing with BCF,their absorption spectra are red-shifted.Further absorption spectroscopy titration experiments found that TPD-4-Py is more easily coordinated with BCF,and the maximum absorption peak of TPD-4-Py and BCF complex is the maximum absorption peak of TPD-2-Py and BCF complex.Shifting 20 nm indicates that the substitution position of pyridine has an important influence on the coordination ability of BCF,and further adjustment of the optical band gap can be achieved by changing the position of pyridine substitution.The device studies of OFETs show that TPD-2-Py is a p-type material with a mobility of 2.96×10-6(cm2 V-1 s-1)and a mobility of 5.29×10-6(cm2 V-1 s-1)after annealing at 60 ?.The performance of the device is poor,which may be due to the shorter conjugate length of the molecule.2)Polymers P-1 and P-2 with dithiophenimide and 4,5-diazafluoren as the core were designed and synthesized.The 4,5-diazafluoren-9-one in the P-1 backbone was modified with malononitrile to reach P-2.We first characterized it by UV-Vis absorption spectroscopy,and studied the optical band gap of the polymer and metal after coordination.The experimental results of UV-Vis absorption spectroscopy show that the band gap of P-1 is significantly shifted after coordination with metal ions,and P-2 cannot coordinate with metal ions due to the strong electron pull of cyano group.Second,we conducted a detailed study of the performance of the P-1 OFETs device.The film of the device is a solution ruthenium method.The experimental results show that P-1 is an n-type semiconductor material,and the device performance is optimally 0.01186(cm2 V-1 s-1)under annealing conditions at 160 ?.When 3%CuSO4 was added,the optimum performance of the device was 0.0497(cm2 V-1 s-1).The AFM results show that as the amount of CuSO4 increases,it helps to change the flatness of the film and improve the mobility of the device.The mobility of P-2 was 0.0025 cm2 V-1 s-1,and the performance did not change after annealing.The film quality of P-3 is too poor to prepare an OFET device.3)We designed and synthesized two small molecules with azaindole as the core and capping with pentafluorobenzene and cyano,and characterized their properties:(1)The LUMO level of the material 23 is-3.99 eV,and the thermal decomposition temperature exceeds 300 0 C,which has good stability.We hope to obtain an n-type semiconductor material for vacuum evaporation,and the device is being tested.(2)Infrared and Raman spectroscopy of compound 27 showed that the nitrile-based vibration peaks appeared at lower wavenumbers of 2097 cm-1 and 2198 cm-1,which is generally considered to be the absorption of conjugated nitrile groups,and the presence of a parent nucleus The characteristic absorption of azaindole indicates that its ground state is a diradical state.Theoretical calculations show that the most stable structure of compound 27 is open-shell singlet free radicals.Further characterization of the diradical properties of Compound 27 is ongoing.