The Synthesis Of Donor Materials And Optimiaztion Of Device Performance For Polymer Solar Cells

It is clear that the current energy regimen,which relies on nonrenewable,has unsustainable consequences for societal and environmental issues.The only completely renewable energy capable of meeting the world's huge and growing energy needs is solar power.Solar cell devices,which convert solar energy into electricity,are one of the most potential and efficient technologies for capturing solar energy.Organic solar cells have received extensive attention due to their advantages of light weight,low cost,and the ability to fabricate flexible large-area devices,and have been rapidly developed in recent years.It is of great significance to improve the performance of the device by obtaining the excellent donor material by structural design of the active layer material.In this thesis,a series of donor polymers were designed and synthesized,and batteries were prepared to study photoelectric properties.The main work is summarized as follows:(1)A novel donor polymer PSBDT-TT-EFT was constructed by introducing thieno[3,2-b]thiophene into thiophene units based on benzodithiophene(BDT)and thieno[3,4-b]thiophene(EFT)unit.Although PSBDT-TT-EFT has a relatively broad absor:ption spectrum and a suitable energy level,the active layer does not form an ideal continuous interpenetrating network for charge transport collection,which results in lower carrer mobility.The optimal performance of the solar cell prepared with PC71BM is 2.32%.It shows that the structural change affects the original transport structure of the charge.Although the addition of thiophene has a certain effect on improving the planarity of the molecule,it destroys the original structure of the material and hinders the charge transport and collection.As a result,it has a great influence on the performance of the device.(2)Using benzodithiophene-4,8-dione(BDD)as the acceptor unit and thiophene as the donor unit,two kinds of polymer donor materials PIT-BDD and P3T-BDD based on different thiophene numbers were syntihesized by a simple procedure.P1T-BDD has poor solubility,and the morphology of P1T-BDD was found to be poor by AFM characterization.The effect of the number of thiophene donors on device performance was investigated.After blending with PC71BM,The device performance achieved 1.23%and 6.96%,respectively.This indicates that the increase of the number of thiophene units can increase the intermolecular force,which can promote the carrier mobility and finally obtain high short-circuit current and fill factor.The results show that the synthesis of a simple Polymer with thiophene as a donor is a key step in reducing the cost of organic solar cells and maintaining device performance.(3)A novel D-A conjugated wide band gap polymer PSBDB-TT based on BDT and BDD units with 3-octylthieno[3,2-b]thiophene units as ?-bridge was designed and synthesized.The planarity of the molecular structure is increased by changing the type of n bridges.This polymer is blended with different acceptor to prepare the devices.Devices of PSBDB-TT:ITIC achieve a high efficiency photoelectric conversion efficiency of 9.02%,and PSBDB-TT:PC71BM fullerene system devices have a photoelectric conversion efficiency of 4.73%.The results show that the choice of alkylation and thiophene units as ?-bridge in conjugated polymers is a potential and effective method to improve the photovoltaic performance of polymer solar cells.It also has the potential to increase further by introducing electrophilic atoms,fabricating inverted devices or using other small molecule acceptors.