Design,Synthesis And Performance Study Of Starshaped Non-Fullerene Acceptor Materials

Organic solar cells have attracted widespread attention due to their wide range of raw materials,light weight,easy processing,low harmful impact on the environment,good film formation,and large-area preparation.In the field of organic solar cells,non-fullerene acceptor materials have the advantages of suitable LUMO energy level,higher electron mobility,wider sunlight absorption spectrum,and good energy level matching with the donor unit.Therefore,the design and development of non-fullerene acceptor materials for organic solar cells with high photoelectric conversion efficiency,low cost,good stability and solution processability is essential for the continuous development and commercialization of solar devices.This thesis starts with the design and synthesis of high-efficiency acceptor-donor-acceptor(A-D-A)type non-fullerene acceptor materials,using different central core units,side chain structure and conjugated fused-ring arm units.And at the end groups,it is modified with a strong electron-withdrawing group with F atoms.The type of the core unit,the main chain structure and side chain structure of the fused-ring molecule are acted as innovative points,combined with the different structure of the conjugated molecule,multiple stacking methods,high purity,good film-forming properties and other advantages.A series of high-efficiency star-shaped non-fullerene acceptor materials are designed and developed.On this basis,further preparation and optimization of the organic solar cell device have been done to control the topography finely and match the energy level reasonably between donor and acceptor materials,with the purpose of exploring the relationship between donor and star-shaped acceptor materials and performance.Specifically,this thesis is mainly divided into the following five parts:The first chapter briefly introduces the research and development background of organic solar cells,and then describes the working principle of organic solar cells.Finally,starting from the research background of commonly used active layer acceptor materials,it introduces the research history and development status of acceptor materials in detail.The focus is on the development status of non-fullerene acceptor materials.At the same time,this chapter also explains the advantages of constructing star-shaped small molecule non-fullerene receptor materials,and condenses the research content and innovative ideas of this thesis from the direction of star-shaped small molecule nonfullerene receptor materials.In Chapter 2,star-shaped small molecule non-fullerene receptor materials substituted by different central core units are designed and synthesized.Firstly,the dominant receptor molecule is introduced into the central benzene ring unit to synthesize star-shaped receptor molecule Ph IDC8IC-F.And then expand the conjugated structure of the central core unit and introduce heteroatom S to synthesize the star-shaped acceptor molecule BTTIDC8IC-F.BTTIDC8IC-F exhibits a red-shifted UV-visible absorption spectrum and a narrow optical band gap.PBDB-T is used as a donor material to make devices.After optimization,BTTIDC8IC-F exhibits a higher open circuit voltage and fill factor,although the short-circuit current is slightly reduced,but finally an excellent device efficiency of 5.51%is achieved,which is better than the Ph IDC8IC-F with the PCE of 5.23%.In Chapter 3,star-shaped small molecule non-fullerene acceptor materials with arm units using different side chain structures are designed and synthesized.To star with,the arm units with solubilizing side chains are introduced into the central core unit of benzotrithiophene to construct a star-shaped molecule BTTIDC8IC-F.And then,use arm units with rigid side chains,which is introduced into the benzotrithiophene structure to synthesize the star-shaped molecule BTTIDTIC-F.Although the rigid side chain can provide additional conjugation effect of the main chain,the large volume of the side chain makes the intermolecular stacking worse and the intermolecular force weakens.Thus,BTTIDTIC-F shows a blue-shifted UV absorption compared to the solubilizing side chain spectrum.PBDB-T is selected as the donor material to prepare the device.Compared with BTTIDC8IC-F,the open circuit voltage,short circuit current and fill factor of BTTIDTIC-F are all reduced,and the device efficiency of 4.31% is obtained,which is much lower than that of the solubilizing side chain,showing 5.51% power conversion efficiency.In Chapter 4,star-shaped small molecule non-fullerene acceptor materials with arm units of different fused-ring structures are designed and synthesized.The IDT is introduced as the arm unit into the central core unit of benzotrithiophene,and IC end group with fluorine is modified to synthesize the star-shaped molecule BTTIDTIC-F.And then,the arm unit structure is expanded.IDTT is acted as the arm unit introduced into the benzotrithiophene central core unit with the same modification of fluorine-containing IC end group to synthesize BTTIDTTIC-F.Due to the expanded fused-ring structure of the BTTIDTTIC-F arm unit,the carrier transmission channel is expanded and the intermolecular force is enhanced.Compared with BTTIDTIC-F,BTTIDTTIC-F shows a redshifted ultraviolet absorption spectrum.Based on PBDB-T,the open circuit voltage,short circuit current,and fill factor of the device prepared from bulk materials is effectively improved,the PCE of BTTIDTTIC-F reach 4.86%,exceeding the efficiency of 4.31% based on BTTIDTIC-F.The fifth chapter summarizes the ideas and research content of this thesis,also provides certain ideas for the further exploration direction of star-shaped non-fullerene acceptor materials.