Study On Self-assembly Of Polythiophene Derivatives

Polymer photovoltaic devices,such as solar cells,transistor devices,and photodetectors,have attracted widespread attention due to their many significant advantages-multifunctional materials,low cost,low weight,and good flexibility.Polythiophene derivatives as a class of conjugated polymers have important and extensive applications in optoelectronic devices.We studied the self-assembly of polythiophene and its derivatives,and strived to find out more self-assembly rules and create more value in practical applications.We selected the NTZ12 molecule as the study object.Under atmospheric conditions,the self-assembled structure of NTZ12 on the highly oriented pyrolytic graphite surface was synthesized and characterized by scanning tunneling microscopy.We chose the typical polythiophene molecule P3HT as the research object.In this dissertation,the self-assembly of polythiophene derivatives was investigated.The morphology of the prepared films was characterized by STM,AFM and SEM.Based on the mixed solvent method,the process of preparing P3HT nanowires was systematically studied.P3HT can be self-assembled under the conditions of water bath and slowly cooling and under the action of anti-solvent to form nanowires and prepare highly oriented P3HT thin films by spin coating.In our work,the absorption spectrum of P3HT showed a red shift after the water bath was slowly cooled in a good solvent,which indicated that the water bath and the slow cooling could produce higher order P3HT aggregates in the solution.In addition,the anti-solvent action allows the P3HT aggregates to precipitate rapidly,facilitating self-assembly on the substrate.We found in our work that the solution's dissolution temperature,concentration and spin coating rate have a significant effect on the yield of nanowires.The higher the dissolution temperature,the higher the yield of nanowires and the better the degree of film ordering.If the concentration of the solution is too low or too high,the size of the nanowires will be affected,thereby affecting the orderliness and flatness of the film.In addition,the spin-coating rate of the film affects the volatilization rate of the solvent,which in turn affects the deposition of the nanowires on the substrate.For our experimental conditions and the characteristics of the P3HT material and the solvent,a spin speed of 3000 rpm and a spin time of 60 s are preferred spin-coating conditions.Through systematic research,we found that when the solution was dissolved at 90?,the solution was 7 mg/ml and spin-coated at 3000 rpm,the P3HT film with the best degree of ordering could be obtained.We have proposed an innovative mixed-solvent method that dissolves at 90 ?overnight-directly slowly cools-mixes the anti-solvent-a spin-coating process.Our research work has reduced the water bath heating step and shortened the reaction time for preparing the thin film by the mixed solvent method.We apply the high-order P3HT layer prepared by the mixed solvent method to organic transistor devices and perform electrical performance tests.The test results show that the performance of the device is significantly improved compared to devices that are spin-coated with P3HT layers.The switching ratio increased by 1033%,and the carrier mobility increased by 150%.This is because in the P3HT layer self-assembled by the mixed solvent method,there is a better ?-electron channel in the self-assembled structure of P3HT,and the electron transport capability is greatly improved.