Synthesis And Photovoltaic Device Research Of High-performance Non-fullerene Small-molecule Acceptor Materials

Organic solar cells(OSCs),as a class of new energy devices,have become a research hotspot in academia in recent years.Compared with inorganic silicon cells,organic solar cells can be processed by a low-cost method and have better mechanical flexibility.Electron acceptor materials for organic solar cells include fullerene derivatives,conjugated small molecules,and polymers.Among them,small-molecule acceptor materials have been extensively researched due to their favorable features such as strong structural tailorability,easy purification,and no molecular weight distribution.The champion efficiencies of organic solar cell devices based on small molecule acceptors are constantly being refreshed.This thesis aims to develop new and efficient acceptor materials based on organic small molecules.From the view of molecular engineering,we synthesized a series of organic small molecules with fused ring structures by tailoring the backbones,side chains and end groups and blended them with suitable donors to prepare organic solar cell devices,realizing performance-regulation from molecular structures.First,the classic conjugated fused ring structure,namely,indacenodithiophene(IDT)unit is selected as the prototype,and the B←N coordination bond is embedded into the conjugated skeleton.The phenyl and thienyl aromatic groups are selected to stabilize the electron-deficient center of the boron atom and two chemically stable fused-ring organic small molecules BNIDT-Ph and BNIDT-Th were obtained and applied to organic solar cell devices.Subsequently,we selected benzothiadiazole unit as the core and synthesized three molecules,i.e.,SS11-4F,AS12-4F,and BTP-C16-4F,with different degrees of skeleton conjugation by fusing with different numbers of thiophenes.This is to explore the effects of the sizes of the conjugated plane of the molecular skeleton on the performance of organic solar cells.Studies have shown that from SS11-4F to AS12-4F and BTP-C16-4F,with the enlargement of the skeleton conjugation,the absorption of molecules can be effectively broadened,and the light-electric conversion efficiencies can be improved from 10.50% to 14.05% and 15.66%.Finally,we optimized the end group and introduced a single chlorine atom at the end group to synthesize BTP-2Cl.We compared it with the Y5,with no chlorine atoms at the terminal groups and the Y6-4Cl molecule with two chlorine atoms at the terminal groups to study the effects of chlorine atoms in the terminal group on the performance of OSCs.Studies show that compared with Y5 and Y6-4Cl,devices based on BTP-2Cl: PM6 shows a better morphology,resulting into the highest device efficiency of 15.34%.The research results in this thesis provide new ideas and new methods for the design and synthesis of new materials.