| With the continuous consumption of fossil energy,the energy crisis and environmental problems become increasingly severe.Therefore,solar energy has gradually become one of the global research hotspots in recent years,due to the property of converting renewable solar energy into electricity.Organic solar cell is one of the most crucial solar energy cells,in which have many advantages,including diverse and controllable material structures,simple preparation methods,light weight,flexibility,and large-area low-cost production,making the organic solar cell a promising device in the application of wearable electronic devices,architectural glass,automotive smart window systems and so on.The light-absorbing acceptor and donor materials are the basis and key composition of the organic solar cells.Designing and synthesizing high-performance donor and acceptor materials are an important way to improve the photovoltaic performance of the organic solar cells.This thesis focuses on,on one hand,a new type of electron donor unit,diindenobisthiophene.Then introducing different thiophene bridges to adjust the bandgap,energy level,light absorption range,solubility,and molecular packing.Three new types of soluble small molecule receptor materials were successfully synthesized through ten-step chemical reactions,and then characterized based on their thermal,optical,electrochemical,and photovoltaic properties.On the other hand,a D-A molecular structure is used to design and synthesize a series of small molecule donor materials that can be evaporated in the vacuum,giving a deep insight into understanding the relationship between molecular structures and material properties.The work of this thesis includes the following three parts:1.The diindenobisthiophene with six-membered unit(DITT)was designed and synthesized as a strong electron-donating unit,and then bridge dicyanoindanedione unit by monothiophene or alkoxythiophene.As a result,two new small molecule organic solar cell acceptors(A-1,A-2)were obtained with the molecular configuration of A-πD-π-A.Both meterials show similar molecular orbital levels,due to the large πconjugated planes of diindenobisthiophene.Accordingly,their optical band-gaps can reach around 1.70 eV,with strong light absorption in the near-infrared region.However,the A-2 molecule is better than the A-1 molecule in terms of the solubility and photovoltaic performance due to the introduction of the alkoxy side chains,leading to better photoelectric conversion efficiency of 5.40%.2.A new type of small molecule of organic solar cell acceptor material(A-3)was synthesized using diindenobisthiophene,a strong electron-donating unit,bridged with dicyanoindanedione pulling electronic unit by thieno[3,4-b]thiophene.Compared with A-1 and A-2 molecules,the A-3 molecule has a wider π conjugate range,due to the introduction of the thieno[3,4-b]thiophene.The structure is beneficial to the charge transfer within the molecule and makes the light absorption a significant red-shift,resulting in a strong absorption even in the range from 550 nm to 820 nm.Accordingly,the optical band gap is 1.55 eV,and the HOMO level and LUMO level are-5.55 eV and-4.00 eV,respectively.However,the preliminary photoelectric conversion efficiency of device based on A-3 is only 0.38%at present due to the limited solubility.3.A series of small molecule donor materials for vacuum-deposited organic solar cells were designed and synthesized.Ten new type of D-A asymmetric small molecules donors which can be evaporated in the vacuum were synthesized using benzothiadiazole(BT)as the strong-drawing electronic unit,with different electrondonating units including diindenobisthiophene six-membered unit(DITT),benzothienopyirole unit,benzobisthiophene unit,bisthienopyrrolethiophene unit,and other structures,laying a solid foundation for our next step to build vacuum-evaporated organic solar cells and select high efficient active layer materials. |
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