Synthesis Method Of Fused-ring Compounds And Side-chain Engineering Of Polymer Donors

Organic solar cells are thin,flexible and solution-processable,which have attracted extensive attention from the scientific community and industry.Donor and acceptor materials are the core of organic solar cells,and also the research frontier and hotspot in the organic photovoltaic field.With the rapid development of highperformance non-fullerene fused-ring acceptors,the research on matched high performance polymer donor materials is relatively lagging behind.In the early stage,our research group developed a one-step conjugated five-membered ring method to synthesize naphthalenothiophene imide(NTI)electron-deficient monomers,and the devices prepared based on the polymer of this monomers have excellent photovoltaic performance.However,the research of wide applicability of synthesis method and the relationship between the structure and properties of polymer donor materials are still lacking.Therefore,we intend to explore the wide applicability of this synthesis method and the influence of side chains of polymers on aggregation and photoelectric physical properties.The following results have been achieved:1.The wide applicability of one-step construction of conjugated fused ring and novel fused-ring compounds: In this part,we explore the wide applicability of onestep method of constructing conjugated five-membered rings through the Suzuki reaction.(1)Dibromo substrates: Several five-member fused-ring compounds were constructed by the reactions of different dibromo substrates and 3,4-bis[(pinacolato)boryl]thiophene respectively,with yields of 56.3%-77.0%.(Pinacolato)boryl substrates: Several five-membered fused-ring compounds were constructed by the reactions of different(pinacolato)boryl substrates and 6,7-dibromonaphthalimide respectively,with yields of 45.7%-79.8% respectively.(2)We further extend the synthesis method of one-step construction of conjugate fivemembered fused-ring compounds to the synthesis of conjugate six-membered fusedring compounds.Six-membered fused-ring compounds were constructed by the reactions of different(pinacolato)boryl substrates and non-rigid substrate 3,3’-dibromo-5,5’-bis(trimethylsilyl)-2,2’-bithiophene,with yields of 55.8%-82.0%.(3)NTI monomers properties.NTI isomers 2-5c and 2-5d were synthesized.The fusing site of thiophene are different,which show different photoelectric physical properties.According to the spectra and single crystal data analysis,the electrons on 2-5d compound thiophene have a tendency to transfer to the conjugate five-member ring.At the same time,through the single crystal data characterization,it was found that 2-5c and 2-5d both have good planarity and abundant intermolecular interactions,which are conducive to carrier transport.This work reveals that the one-step method of constructing conjugate five-membered rings by Suzuki reaction has good substrate applicability and can be extended to one-step construction of conjugate six-membered rings.At the same time,the study of NTI monomers revealed the reasons for their excellent properties and the effect of thiophene fusing position on NTI monomers.2.Side-chain engineering research of polymer donor materials: The polymer PNTB-E,PNTB-EF and PNTB-TFB were synthesized by introducing 4-(acetyloxy)-butyl,4-(2’,2’,2’-trifluoroacetyloxy)butyl,4-hexyl-2,3,5,6-tetrafluorobenzyl side chains into the NTI monomer of polymer to study the effect of the enhancement of intermolecular force and charge transfer on the performance of photovoltaic devices.The HOMO and LUMO levels of PNTB-E and PNTB-EF are basically the same,and the HOMO level of the PNTB-TFB can be reduced by the electron-absorbing effect of the 4-hexyl-2,3,5,6-tetrafluorobenzyl side-chain on the main chain.The film and solution absorption spectra showed that the phenyl side chain extended the π-conjugated system,and the side chains significantly affected the film accumulation of the polymers.AFM test results show that the introduction of fluorine atom on the side-chain increases the roughness of the films,which is beneficial to increase the contact area between the active layer and the interface layer,achieving more efficient carrier transport and extraction.By preparing PNTB-TFB:BO-4F,PNTB-E:N3-4F and PNTB-EF:N3-4F devices for testing,the power conversion efficiency(PCE)of16.88%,14.29% and 15.64% were obtained respectively.It is shown that the introduction of large polarity and fluorinated side chains can enhance the interaction and aggregation of molecules,which are conducive to carrier transport and extraction.In this part,the research on the influence of different side chains on the performance of photovoltaic devices has guiding significance for the design and synthesis of polymer donor materials.