Design And Synthesis Of Benzodithiophene Conjugated Polymers And Their Applications In Organic Photovoltaic Devices

As a unit with excellent performance,benzodithiophene(BDT)is often used in the design of the main chain skeleton of polymers,which has greatly promoted the development of bulk heterojunction organic solar cells.Among them,side chain engineering plays an important role in regulating charge transport,material solubility,processability,aggregation and crystallization behavior in the organic photovoltaic active layer.In addition to the structural design of the material,the use of solvent additives in the preparation process of the device is also an important means to improve the photoelectric conversion efficiency of organic solar cells.However,the addition of solvent additives as the third component can improve the photoelectric conversion efficiency(PCE),but also complicates the device manufacturing process.Therefore,the use of side chain engineering to replace solvent additives plays an important role in realizing high-performance organic solar cells.The active layer material of bulk heterojunction organic solar cells is a blended system formed by polymer donors and small molecule acceptors.Due to the small size of the small molecule receptor,there is a higher degree of freedom in the active layer,and self-aggregation easily occurs under heat or light conditions,which degrades the performance of the device;at the same time,its preparation process is complicated.However,the active layer of a single-component organic solar cell requires only one material,which can effectively avoid problems such as dosing and acceptor physical blending.At the same time,its preparation process is simple and its performance is stable.However,there are also single materials and difficulty in phase separation control problem.Therefore,in this thesis,a series of polymers were designed and synthesized with BDT units as a component of the conjugated framework,and by adjusting their side chains,bulk heterojunction organic solar cells and single-component organic solar cells were prepared respectively.Explored the relationship between its photovoltaic performance and structure.The main findings are as follows:1.Designing and synthesizing conjugated polymers with different side chain end groups,PBDB-T-H,PBDB-T-I,PBDB-T-OAc,among which the donor copolymers PBDB-T-I and PBDB-T-OAc shows similar absorption and energy levels,but their photovoltaic device performance has been improved compared to PBDB-T-H.In addition,studies have found that PBDB-T-I and PBDB-T-OAc have higher performance without additives,indicating that these copolymers exhibit self-doping effects during solvent processing.2.Using PBTT-F as the conjugated skeleton and introducing BPTI into the side unit of the polymer,we have designed and synthesized a brand-new dual-cable conjugated polymer by using the "functionalization first,then polymerization" method,then applying the polymer into the active layer of a single-component organic solar cell device,achieving a power conversion efficiency of 2%.The results have found that the property of the strong aggregation of dual-cable conjugated polymers is not conducive to the improvement of power conversion efficiency.