Synthesis And Properties Of Conjugated Oligomeric Optoelectronic Materials Via Direct C–H Arylation Reactions

Due to its clear molecular structure and molecular weight,high crystallinity and orderly stacking characteristics,conjugated organic optoelectronic oligomers can effectively overcome the disadvantages of poor repeatability and excessively wide molecular weight distribution during the synthesis and purification of polymer molecules,thereby improving the performance of optoelectronic devices.However,most research focus on conjugated small molecules and polymers,and the development of organic photoelectric oligomers remains to be explored.The synthesis of organic conjugated materials is the foundation and source of innovation for the research of organic electronics and devices.Developing a simple and efficient synthesis methods play a role in organic optoelectronic.In this paper,through the Direct Arylation of C–H Bonds,diketopyrrolopyrrole(DPP),2,7-dibromo-9,9-dihexylfluorene(DBFL),Iso-indigo(IID),cyclopentadithiophene(CPDT)and carbazole(Cz)are monomers,24 conjugated organic optoelectronic oligomers and their parent polymers were synthesized,and their optoelectronic properties were studied in detail.The main research contents and innovations of this paper are as follows:(1)Through the direct arylation reaction of two C–H bonds between the DPP of the thiophene side group and DBFL,two series of twelve D-A(DPP-Fl)oligomers respectively terminated by C–H and C–Br bonds were synthesized.The structure was confirmed by NMR,Maldi-Tof and elemental analysis.Through UV-vis spectra,cyclic voltammetry and DFT calculations,the changes of the relationship between the structural properties of 12 oligomers and their parent polymers were studied in detail.The one-step synthesis strategy will open up a new direction for the rapid and atom-economic synthesis of long-chain D-A ?-conjugated oligomer materials.(2)The universality of the experimental conditions of the C–H direct arylation was verified.By controlling the feed ratio and the three-pot C–H bond direct arylation reaction,two series of CPDT and IID based donor-acceptor(D-A)type narrow band gap(1.42-1.58 e V)new oligomer and its parent polymer were synthesized,the feed ratio of IID and CPDT is1.5:1,1:1.5 and 1:1 respectively.The optical and electrical properties of these narrow band gap oligomers and polymers have been studied in detail,and they are completely consistent with their corresponding structural evolution.This work provides an effective synthesis strategy for narrow band gap monodisperse long-chain D-A oligomers,and will be of great significance for accurate structural properties research and optical and electronic applications.(3)Using DPP and Cz as the building units,a series of monodisperse conjugated organic optoelectronic oligomers with progressively increasing repeating units were synthesized via one-pot C–H direct arylation,and made a detailed study of its photoelectric properties and the dependence of device performance and chain length.Studies have shown that the PCE of the oligomer increases with the increase of the chain length,and the oligomer O5 with the longest chain length is very close to the PCE of the parent polymer.This study shows that the conjugated organic photoelectric oligomers synthesized by the C–H direct arylation are expected to further improve the device efficiency of organic solar cells and have certain reference value for the design of new conjugated organic photoelectric oligomers.