Synthesis And Properties Of Naphthalene Diimide-based Acceptor Copolymers Based On Triple Bond Bonding

Organic thin film transistors(OFETs)are widely applied in organic electronics due to their advantages of flexible,light-weight,large-area and so on.Organic semiconductors as an active layer in OFETs,play an important role in charge carriers transportation.The semiconducting molecular structures and molecular arrangements in solid state determine thermodynamic/chemical stabilities and charge carrier mobility of the corresponding OFET devices.Accordingly,the design and synthesis of organic semiconductors with excellent comprehensive properties is of great significance.Naphthalenediimides(NDIs)are the popular acceptor moieties.The different donors were copolymerized with NDIs units and the HOMO/LUMO energy levels,band gap,and charge transport characteristic of the corresponding polymers could be commendably tuned.Accordingly,this thesis pay attention to the design and synthesis of naphthalene diimide-ethynylene-basedπ-conjugated polymeric semiconductors,and evaluates their related physical/chemical properties as well as the structure-performance relationship.The main contents are outlined as follows:1.Three new ethynyl-linked 1,2,5,6-naphthalenediimide based copolymers(P1,P2 and P3)comprising of 2,1,3-benzothiadiazole,benzene and 1,4–bis(dodecyloxy)–benzene units,respectively,were designed and synthesized.The thermal,optical,electrochemical as well as charge transport properties were studied.P1,P2 and P3 in solution or in thin films exhibited fluorescence,respectively,and their band gaps(2.02 ~ 2.25 eV)are lower than that of PPEs(~ 2.5 eV).P1,P2 and P3 showed the comparable LUMO energy level about- 3.5 eV.The HOMO energy levels of P1(- 5.67 eV)and P3(- 5.57 eV)was increased by 0.1 and 0.21 eV,respectively relative to P2(- 5.77 eV).To investigate the charge transport properties of P1,P2 and P3,their bottom-gate top-contact OFETs were fabricated.P1 and P2 are the first two examples of n-channel semiconductors for1,2,5,6-naphthalenediimide based copolymers in OFETs with the electron mobility of up to10-3 cm2 v-1 s-1,while P3 exhibited only p-type semiconductor behavior.The above results indicate that the fine-tuning of units of 1,2,5,6-NDI-based copolymers could regulate the corresponding energy level and the behavior of semiconductor.2.Two new ethynyl-linked dibenzophosphole based copolymers(P4 and P5),comprising of 1,4,5,8-NDI and 1,2,5,6-NDI,respectively were designed and synthesized.The physicochemical properties of copolymers were studied and compared with each other.It was found that polymers exhibited different optical and electrochemical characteristics.The absorption spectra of P4 and P5 showed the complementarity feature.P4 and P5 in solution or in thin films exhibited fluorescence,respectively but the fluorescence of P4 was very weak.The two-photon fluorescence of P4 was investigated.The data demonstrate that P4 possess the second-order nonlinearity features.Bttom-gate top-contact OFETs based on P4 showed n-type semiconductor behavior,while OFETs based on P5 have no signal.