Design And Synthesis Of Novel Conjugated Polymers For Field Effect Transistors

Comparedwithconventionalinorganicsemiconductormaterials,organic semiconductor materials,especially polymer semiconductor materials were considered to be excellent materials for making large-area flexible device,owing to their unique advantages of good film-forming,good flexibility,low cost,lightweight and so on.However,the scarcity of high-performance polymer semiconductors limits their further application and development.In this thesis,we herein design new electron-deficient building blocks,develop novel molecular architecture,and use end-group effect to improve the performance of polymer materials.In addition,the relationship between their structure and performance is also discussed.The main contents of this thesis are summarized as follows:In chapter two,the design and synthesis new electron-deficient building blocks become very important for improving the performance of polymer semiconductors in organic field-effect transistors.In view of the lack of strong electron-deficient acceptor units,we synthesized two new electron-deficient acceptors units IVI and F₄IVI,and the corresponding polymer semiconductor materials PIVI2T and PF₄IVI2T Because of the strong electron-withdrawing ability and extended?-conjugated system of IVI and F₄IVI,polymer semiconductor material PIVI2T and PF₄IVI2T have deep lying HOMO/LUMO energy levels and strong intermolecular interactions.Compared to PIVI2T,PF₄IVI2T containing fluorine atom has stronger inter-and intramolecular interactions,the HOMO/LUMO energy levels low up to-5.74/-4.17 eV.PF₄IVI2T also exhibits smaller?–?stacking distance?3.53??and more ordered molecular packing.The properties of PF₄IVI2T result in an excellent ambipolar charge transfer performance and promisingapplication prospect in logic circuit with electron and holemobilities of up to1.82 and 1.03 cm²V^-1s^-11 in ambient.The results indicate that F₄IVI is a promising electron-withdrawing unit to construct high-performance polymer semiconductors,which provides a new insight to explore the relationship between structure and propertyIn chapter three,exploring new molecular architecture is vital for designing high performance ambipolar polymer semiconductors.We designed and synthesized a new ambipolarpolymersemiconductormaterialsDPP-2T-DPP-TBTwith A₁–D₁–A₂–D₂–A₃–D₃ architecture,in which three electron-deficient acceptors and three electron-rich donors act as the repeat unit in thepolymerbackbone.DPP-2T-DPP-TBT exhivits deep-lying HOMO and LUMO energy levels of–5.38/–4.19 eV,and enhance intermolecular interactions,which is beneficial for hole and electron injection and intermolecular hopping through?–stacking.Additionally,small and similar m_h*/m_e*of DPP-2T-DPP-TBT indicate it has well balanced and effective intramolecular charge transports for electrons and holes.All these factors lead to superior ambipolar charge transport characteristic of DPP-2T-DPP-TBT and associated complementary-like circuits.The hole and electron mobilites of DPP-2T-DPP-TBT reach up to 3.01 and 3.08 cm²V^-1s^-1,respectively.The gain value used in a complementary-like inverter up to 171.The performance is among the best ofambipolar OFETs and complementary-like circuits,especially in top gate OFET device with low cost glass as substrates.These results indicate that“A₁–D₁–A₂–D₂–A₃–D₃ architecture”is a good way for designing and synthesizing high performance balanced ambipolar polymer semiconductors.In chapter four,Strong electron-withdrawing groups were introduced to polymer materials can effectively reduce the molecular energy level of polymer materials and form moreorderedmolecularpacking.Onthisbasis,weintroducedstrong electron-withdrawing groups to the both ends of polymer material PDPP-TT,and got two new polymer material PDPP-TT-1 and PDPP-TT-2,The thermal stability,photophysical and charge transfer performance of these three polymers were researched.The better performance of PDPP-TT-1 and PDPP-TT-2 relative to PDPP-TT is attributed to the introduction of end-group,leading to better crystallinity.In chapter five,diarylethene is a typical organic photochromic compounds and the conjugation system can be extended under a certain wavelength of ultraviolet light.In this chapter,we synthesized a new polymer semiconductor materials PDPP-DAE,in which diarylethene and diketopyrrolopyrrole are used as a donor and acceptor,respectively.The photophysical and electrochemical properties of PDPP-DAE werestudied.The small optical bandgap and low molecular energy levelmay indicate good charge transfer performance for PDDP-DAE.In addition,it can be observed increased maximum absorption intensity and decreased HOMO/LUMO energy levels under a certain wavelength of ultraviolet light,likely implying that PDDP-DAE is promising photoconductive polymer semicondutors.