Synthesis And Photovoltaic Properties Of Polymer Donor Materials Based On Benzothiadiazole-Benzodithiophene Units

Solar energy is one of the promising renewable energy sources,solution-processed polymer solar cells have attracted attention due to their potential advantages such as low cost,light weight,flexibility,and ease of large-area manufacturing based on film solar cells.The power conversion efficiency of the bulk heterojunction polymer solar cells reported so far has exceeded 14%.The properties of polymer donor materials play a key role in the many influencing factors.Therefore,a high-efficiency polymer solar cell is obtained by designing and synthesizing a novel polymer donor material.A series of polymer donor materials were designed based on benzothiadiazole(BT)and benzodithiophene(BDT)in this paper.Applied to organic photovoltaic devices,the power conversion efficiency obtained by optimizing its performance is 4.73%.The main research work is as follows:1?In Chapter 3,based on the design concept of region asymetry two asymmetric polymers(PR1F and PR2F)were synthesis by Stille coupling reaction by using benzodithiophene,thiophene(T)as donor units and fluorine substituted benzothiadiazole as acceptor unit.Both materials have a broad absorption spectrum of 300-700 nm,and the optical band gaps of PR1 F and PR2 F are 1.73 eV and 1.75 eV,respectively.The thermal stabilities of PR2 F and PR1 F are good enough for their application in PSCs.A conventional PSC architecture of ITO/PEDOT:PSS/active layer/LiF/Al was fabricated to evaluate the photovoltaic performance of the two polymers PR2 F and PR1 F as donor materials.It is shown that the PSCs based on PR1 F showed a PCE of 2.92%,while PR2F-based device substantially improves the efficiency to 4.73%.2?In Chapter 4,based on design idea of 2A-oligothiophene structure,the two polymers(PTT-BDT and PT-BDT)were synthesis by benzo[1,2-b:4,5-b']dithiophene,thiophene as a donor units,and thiophene and thienothiophene as ? bridges linking two fluorine-substituted benzothiadiazole units.Both donor materials have a wide spectrum of 300-700 nm,as well as lower HOMO and LUMO levels matching the fullerene acceptor material.At the same time,the two polymer donor materials also have a high ability to transport holes.