Design,Synthesis And Photovoltaic Properties Of Dithienocyclohexanedione Conjugated Polymers

With the development of science and technology,environmental pollution and energy shortages have become increasingly prominent,and there is an urgent need to develop green energy to replace traditional resources.In recent years,organic solar cells have become a research hotspot because of their potential for large-area applications and the production of flexible batteries.The active layer as the light absorbing layer is a key factor affecting the performance of the solar cell.At present,the energy conversion efficiency of single-junction organic solar cells based on bulk heterojunction structure has exceeded 15%.Among them,the D-A type donor polymer PBDB-T exhibits excellent performance as a donor material in a non-fulilene solar cell.Based on the donor polymer PBDB-T,the main chain structure of benzodithiophene(BDT)and dithienocyclohexanedione(BDD)was used to synthesize new donor polymers and have them in the airport.The application of effect transistors and organic solar cells is being studied.The details are as follows::1.Design and synthesis of a new donor polymer PSBDB-T: a sulfur atom was introduced at the position of the carbon chain on the thiophene of the dithienocyclopentadione(BDD)unit to synthesize a new donor polymer PSBDB-T.The polymer PSBDB-T has good thermal stability and a wide absorption range from 300 nm to 700 nm.Since the introduction of a sulfur atom lowers the HOMO level of the polymer,the open circuit voltage of the battery device is improved,but the energy conversion efficiency can only reach 5% in the non-fulilene solar cell device.Compared with the cell efficiency of the similar polymer PBDB-T of 8.8%,it is significantly lower.By having an organic field effect transistor and a space charge limiting current,the hole migration efficiency in the polymer is measured to be significantly lower,resulting in a decrease in device performance.2.Design and synthesis of new donor polymers PBDB-T-C and PBDB-T-CS: introduction of methoxy and chlorine atoms on benzodithiophene(BDT)side chain thiophene to synthesize new donor polymer PBDB-T-C and PBDB-T-CS.It was found that the two polymers have similar absorption range from 300 nm to 700 nm,but due to the introduction of chlorine atoms,the HOMO level of the polymer PBDB-T-CS is lower than the polymer PBDB-T-C,resulting in a polymer preparation device.The choice of acceptor material is different,and the polymer PBDB-T-CS device has a smaller range of acceptor absorption peak overlap.Through the comparison of battery device performance,the device efficiency of polymer PBDB-T-C can reach 6.42%,and the efficiency of polymer PBDB-T-CS device can reach 8.50%.The hole mobility and electron mobility of the polymer PBDB-T-CS were more balanced by the space current limiting charge.The morphology of the film was observed by atomic force microscopy.The phase separation scales of the polymers PBDB-T-C and PBDB-T-CS were significantly different.Since the addition of chlorine atoms affects the crystallization properties of the polymer,the hole mobility and the electron mobility can be balanced,and the device performance is improved.