Isoindigo-Based Donor-Acceptor Conjugated Polymers And Organic Thin-Film Transistors

Recent years,organic thin-film transistors(OTFT)have attracted a mountain of attention.Donor-Acceptor conjugated polymers(D-A CPs)have become one indispensable kind of high-mobility material due to their strong intermolecular interaction and tunable energy levels.However,the relationship of structures and properties of D-A CPs needs further research.What's more,the development of air-stable n-type CPs falls behind,which to some extent limits the application in organic circuits and relative electronic devices.Focus on these problems,we developed an efficient method to synthesize asymmetric alkyl chain substituted isoindigo(IID),inspired by directed aldol condensation,and systematically studied how regioregularity affected properties of CPs.Also,we developed a new kind of strong electrophilic bis-IID unit,and subsequently constructed air-stable n-type CPs.The main results and contributions are:(1)An efficient method to synthesize asymmetric IID has been developed.Based on the method,a series of conjugated polymers with different alkyl side chain regioregularities have been synthesized.Little impact on absorption spectrum of regioregularity was observed,while the size and branching point position of alkyl chains showed obvious influences on it.Although regioregular CPs enjoyed better solid packing,their OTFT performance were less than satisfactory,due to their poor solubility and film-forming property.(2)Built a new kind of strong acceptor units,bis-IID.Copolymerizing bis-IID derivatives and BT/4FBT,we got a series of D-A CPs.Trough introducing different numbers of F/N atoms into the backbones,the EHOMO and ELUMO of the polymers were successfully tuned in broad ranges and subsequently the transport type of carriers turned from ambipolar type to n-type.P2F-4FBT,P4F-4FBT and P2N2F-4FBT enjoyed low energy levels and were n-type CPs,and mobilities of which were up to 0.93,0.71 and 1.24 cm2/(V·s),respectively.