| Isoindigo?IID?and its derivatives are the common acceptor units of donor-acceptor?D-A?conjugated polymer semiconductors because of their excellent electron deficient properties,coplanarity and the capacity of structural derivatization.However,the high frontier molecular orbital of IID limits its application in n-type organic semiconductor materials.In this paper,the electronic transport properties of isoindigo based conjugated polymers were optimized by a specific molecular design strategy.Two groups of novel D-A conjugated polymer materials based on IID derivatives were successfully prepared by means of targeted molecular design strategy.Their thermal stability,optical properties,electrical properties,film microstructure and morphology,field-effect transistor performance and air stability were characterized and investigated.The main contents of this paper are summarized as follows:?1?Six high-performance D–A conjugated polymers,PBIID1-BT?P1??PBIID2-BT?P2??PBAID1-BT?P3??PBAID2-BT?P4??PBAID3-BT?P5?,and PBAID3-2FBT?P6?,based on the acceptors bis-isoindigo?BIID?and bis-azaisoindigo?BAID?,were designed and synthesized with the donor bithiophene and fluorinated bithiophene.The charge transfer properties of the polymer are significantly changed because of energy level regulation achieved by incorporation of nitrogen and fluorine heteroatoms.Side chain optimization by reducing side chain density and extending branching point positions was shown to significantly influence intermolecular interactions and supramolecular self-assembly.Finally,P6-based OFET devices displayed highly-balanced ambipolar transport properties with the maximum hole mobility of 1.68 cm2 V-1 s-1and electron mobility of 1.37 cm2 V-1 s-1.Both the average hole mobility and electron mobility are up to 1.31 cm2 V-1 s-1 after thermal annealing at 200?.?2?Three unipolar n-type D-A conjugated polymer semiconductors?abbreviated as PNVB,PBABDFV,and PBAIDV?were successfully developed through"strong acceptor-weak donor"strategy that combine strong electron-deficient units and electron-rich vinyl?-bridge.The as-obtained PBABDFV-based OFET devices in bottom-gate/top-contact configuration exhibited excellent field-effect performances under both vacuum and air conditions.In air,the maximum electron mobility reached0.79 cm2 V-1s-1,Ion/Ioff was over 106,and the average Vth was recorded as 25 V.The near-ideal transfer curve of PBABDFV-based OFET device in BG/TC configuration under vacuum was obtained with average mobility reliability factor(rave)reaching88%.On the other hand,PBABDFV-based OFET devices still maintained maximum?e of 0.5 cm2 V-1s-1after 27-day of storage under air due to the kinetic barrier caused by excellent straight-line?-conjugate skeleton and tight?-?stacking distance to prevent water vapor and oxygen from diffusion into the active layer to a certain degree. |
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