Synthesis And Field-effect Properties Of Organic Semiconductors Based On Three Dithienothiophene Isomers

As a new type semiconductor materials,the derivatives of dithienothiophene(DTT)have potential application in organicphotoelectricdevices, the high polarizability of sulphur atoms in dithienothiophene can easily cause multipleforms of intermolecular interactions, such as S-S interactions, S-C interactions, etc, which provide convenient pathway for efficient carrier transportation and benefit for improvingdevicesperformance. However, the effect of sulphur atoms positions on intermolecular interactions and field-effect performances in these isomers is still in a vague state. In order to reveal the relationship between the position of sulphur atoms and intermolecular interactions and divice performance, a series of new organic semiconductors based on three DTT isomers were synthesized, and their electronic and optical properties have been investigated in this dissertation. The main work can be divided into three parts as followed:1) DEP-tt-DTTpossessing sublimation yield of 31%was efficiently synthesized via Wittig reaction with tt-DTT as the building units. By comparing the single crystals with that of DEP-bt-DTTand DEP-bb-DTT, we found that the intermolecular interactions can transform from 3 S-C, 2 S-S in DEP-tt-DTT to 3 S-C, 1 S-S in DEP-bt-DTT and to 4 S-C in DEP-bb-DTT as the sulphur atoms position changing.Combined with the theoretical calculations and devices performances, it can be confirmed thatS-C(or S-?) and S-S interactions benefit for the charge transport, but the S-S intermolecular interaction can sharply weaken the effect of the ?-? intermolecular interaction on the charge transport when they are in the same direction.2) The unymmetric molecular of dithieno[2,3-b:2',3'-d]thiophene(bt-DTT)have two ?-positions with different activities, which can lead to the high selectivity of bromination. Six couples of isomers(the derivatives of bt-DTT), TM-1 and TM-6, TM-2 and TM-7, TM-3 and TM-8, TM-4 and TM-9, TM-5 and TM-10, TM-11 and TM-12 were designed and synthesized using bt-DTTas the core via Wittig reaction, McMurry reaction, or oxidative coupling by CuCl2 and so on. All the target compounds have been purified by vacuum sublimation and characterized by MS, HRMS, elemental analysis.All the intermediate compounds were confirmed by 1H, 13 C, MS, HRMS and IR. All target compounds show goodthermalstability according to the results of TG. OFETs based on these materials were fabricated and characterized. All the materials present field-effect characteristics. For TM-10 and TM-12, the mobility and on/off ratios reach the level of 10-1 and 105, respectively.3) As the derivatives of fused thiophenes with up to seven rings, three new planar oligothienoacenes(HTTA-A with yield of 12%,HTTA-B with yield of 25% and HTTA-C with yield of 17%)were designed and synthesized from bromo-DTT(bt-DTT and bb-DTT), via bromine danceand cross-coupling reaction by the CuCl2 oxidation to generate dimer of DTT, then ring closing reaction of dimer to obtain the target [7]thienoacenes.All the intermediate and target compounds were confirmed by 1H, 13 C, MS, HRMS and IR. In the single crystals of compound 34, which is theprecursors of HTTA-A, the two moieties of DTT are nonplanar and along thevertical direction, but each moiety is approximately coplanar; In the single crystals of compound 41(HTTA-C with TMS protection groups), its molecule presents planar with the lamellar arrangement. There exits multiple short intermolecular interactions including ?-?, S-S and S-? interactions observed in crystal packing, which maybenefit for the carrier mobility when HTTA-C is used as organic semiconductor. These results indicates that these planar[7]thienoacenesmay be the good candidates of semiconductor materials with high-performance.