Syntheses And Photoelectric Properties Study Of Organic Functional Materials Based On Benzodithienothiophene

Organic fused molecules with rigid conjugated structure can promote electron delocalization and facilitate the intermolecular interaction.Thus,they can be used as organic semiconductors.Among fused molecules,air stability of acenes reduces with the increasing number of fused benzene rings.In contrast,fused thiophene and its derivatives show good stability,while their carrier transport capacity is lower than that of the acenes with the same number of aromatic rings.In addition,rigid skeleton leads to the poor molecular solubility,which is not beneficial to the structure characterization,property exploration and further molecular functionalization.To solve the above problems,this thesis inllustates the construction of stable and soluble dithieno[2,3-d;2’,3’-d’]benzo-[1,2-b;3,4-b’]dithiophene（DTmBDT）conjugated molecules,and exploration of the syntheses and photoelectric properties of novel molecular structures based on DTmBDT unit.Their applications in perovskite solar cells（PSCs）,organic field effect transistors（OFETs）,and the structure-property relationship of diradical molecules are further investigated.By Suzuki coupling reaction between triaromatic amine borate and thiophene-ring-brominated DTmBDT,two new types of organic small molecules DTmBDT-TPA and DTmBDT-OMe TPA were constructed in the yields of 69.0%and 55.0%,respectively.The photoelectric conversion efficiencis（PCEs）of DTmBDT-TPA-based PSC is 16.6%.After the introduction of methoxy groups,the PCE of DTmBDT-OMe TPA-based device is increased to 18.2%.It was found that S atoms in thiophene passivated Pb defects in perovskite,which effectively enhanced the stability of PSCs.The PSCs of DTmBDT-TPA and DTmBDT-OMe TPA remain 80%and 90%of their initial efficiencies after storage for 1440 hours under air condition.After device heating at 85℃for 720 hours,76%and 85%of the initial PCEs were maintained,respectively.In order to study the relationship between molecular conjugation length and photoelectric properties,linear molecules with 11 fused rings were constructed.Using DTmBDT as starting material,BBDTB-H,BBDTB-TIPS and BBDTB-Br were synthesized through 6 steps in the yields of 21.5%,17.6%and 8%,respectively.Through the systematic studies,the effects of linear fused molecules with different conjugation lengths on molecular light absorption/emission,frontier molecular orbital energy levels,electrochemical stabilities and aromaticities were clarified.The single crystal of BBDTB-TIPS shows that the length of conjugated skeleton is 22.42?,and crystal packing structure is stabilized by interplanarπ-π,S…S,and S…πinteractions.BBDTB skeleton provides effective channels for carrier transportation.The performance of OFET indicates that BBDTB-H shows p-type semiconductor characteristics(μ_h=2.85×10^-2 cm²v^-1s^-1)and an on/off ratio reaches to 10⁷.On the basis of Chapter 4,two new stable diradicals DTmBDT-O^·and BBDTB-O^·were synthesized via oxidizing 2,6-di-tert-butylphenol linked DTmBDT and BBDTB,respectively.Both of them have wide absorption,narrow band gaps and obvious fluorescence quenching photophysical characters.Compared with DTmBDT,BBDTB with larger conjugated structure is conducive to improve the stability of diradical molecules by extending the conjugation length,extanded the half-life period from 85.6 days to 99.5 days.According to density functional theory（DFT）calculation,the diradical value y₀ of DTmBDT-O^·is 0.92.By means of variable temperature electron paramagnetic resonance,X-ray single crystal diffraction and density functional theory calculation,the existence of a resonant hybrid state between the close-shell quinoidal form and the open-shell diradical form of DTmBDT-O^·is proved.