Synthesis And Photovoltaic Properties Of Non-fullerene Small Molecule Acceptor Materials Based On Porphyrin,Spirofluorene And Indanedione

In recent years,due to the massive use of fossil energy,many problems such as the energy crisis and the greenhouse effect have emerged.Organic solar cell technology can directly convert solar energy into electricity,which is expected to be one of the solutions to the abovementioned problems.The active materials of organic solar cells are generally divided into donor materials and acceptor materials.Among them,non-fullerene small molecule acceptor materials have the advantages of good solubility,adjustable absorption,and easy synthesis.They have attracted the interest of many researchers.This thesis focuses on the design and synthesis of some new non-fullerene small molecule acceptor materials by selecting different electron donating and electron accepting units.In Chapter 2,we synthesized two small molecules PORPDI and PORPDI-2F based on porphyrin core and perylene diimide units.On the side group of the second molecule,we used fluorine atoms to improve the stacking of acceptor small molecule in the active layer.The results show that the fluorine atoms on the side group can impact the absorption.The OSCs based on two acceptors and PBDB-T donor exhibits power conversion efficiencies(PCEs)of 0.82% and 2.87%,respectively.When PTB7-Th was used as the donor instead of PBDB-T,the PCEs of the OSCs based on PORPDI and PORPDI-2F are 1.60% and 2.97%,respectively.The short-circuit current density and fill factor of the devices based on PORPDI-2F are better than those based on PORPDI.These results indicate that the modification with fluorine atoms can improve the photovoltaic performance of perylene diimide and porphyrin acceptor materials.In Chapter 3,we used spirofluorene,2,1,3-benzothiadiazole and dicyano-rhodanine to design and synthesize two non-fullerene small molecule acceptor materials SFABR and SFABTR.Their absorptions can be well complementary with common polymer donor materials.After the device optimization,the OSCs based on SFABR and SFABTR acceptors and PTB7-Th donor show PCEs of 1.33% and 0.76%,respectively.In Chapter 4,we used dicyanoindandione with difluoro,2,1,3-benzothiadiazole,and 4Hcyclopentane [2,1-b:3,4-b’] dithiophene to design and synthesize two non-fullerene small molecule acceptors BTIC4 F and BTIC6 F with the structural characteristics of A-D-A-D-A.In the BTIC6 F molecule,two fluorine atoms in the 2,1,3-benzothiadiazole are introduced.For the none-optimized devices based on PBDB-T donor and BTIC4 F and BTIC6 F acceptors,PCEs of 3.35% and 5.57% were achieved,respectively.Among the photovoltaic parameters,the filling factor of BTIC6F-based devices is improved significantly compared to that of the BTIC4 Fbased devices,suggesting that BTIC6F-based active layer has a better morphology.In the follow-up,we further optimized the BTIC4 F molecular device and finally achieved an efficiency of 7.93%.