Fluoreneyl D-A Small Molecules:Design And Storage Properties

The storage devices based on organic field-effect transistors are widely used because of their advantages such as easy stacking of large scale integrated circuits,non-destructive read-out of logic signals,and better solubility of electret materials.Memory store the charge in the electret material through the electret,the nature of the electret material to a large extent determine the storage performance,so the electret material in the OFET memory occupies a very important position.In existing electret materials,D-A polymer-based memory devices with electrically bistable behavior have been received considerable attention due to attractive features such as rich architectural flexibility,low cost,solution processability and three-dimensional stacking capabilities,and the introduction of D/A unit,causing intramolecular charge transfer,making the molecule has a good storage capacity.However,compared with the polymer,small molecules have a clear molecular structure,low cost,simple,designability,easy to purify,reproducibility,regulation of electronic and structural properties.Therefore,organic small molecules as a study of data storage has practical significance.D/A unit ratio,D/A unit in the side chain or the main chain,D/A unit arrangement order,the difference of the electronic ability between D/A unit,these factors can cause differences in storage performation.Therefore,in order to explore the effect of D/A unit on the performance of memory devices,this paper designs and synthesizes a series of D-A small molecules to explore the performance of different memory devices.In the second chapter,through Suzuki coupling reaction,Friedel-Crafts reaction build H-type D-A small molecule(H-4F,H-4FOH,H-4Py),which takes the electron-withdrawing group of benzothiadiazole as the bridge,aromatic groups fluorene,fluorenol,pyrene and other electron-rich Unit as terminal group.The H-type small molecules with terminal grafting units have good luminescent properties.The fluorescence quantum efficiency of the terminal group is fluoxyn group,which is up to 0.89 in the film,and its solvent-forming dependence is the smallest.The memory devices exhibit nonvolatile properties and write speeds of less than 0.02 s.H-4F molecules have two storage capacity,The storage window is 19.7 V,H-4F molecule,s mobility is 1.1 cm2/vs.The switching current Compared with 5.71×106,H-4Py have the shortest retention time.In the third chapter,the symmetric H-type D-A small molecules,which is bridging electron-withdrawing group with H-type terminal groups,is grafted with Suzuki coupling reaction,Friedel-Crafts reaction,condensation reaction and so on(H-4CHO).The thermal stability and Luminous characteristics of the H-type small molecule with the the terminal-acceptor unit are lower than those of the H-type small molecule which has electron-rich Unit as terminal group.Close to the LUMO level than the H-4F deep,the band gap is wide,is not conducive to the charge from the pentacene tunneling is captured by the electret,the gate voltage of-100 V,the storage window is 56.78 V;The proportion of body units increased,chage have been captured deeply to have less storage sites,which is not conducive to charge storage,H-4CHO small molecule's storage performance is not ideal,But the retention time can reach 104 s.In the fourth chapter,the H-4FOH molecule was connected with benzothiadiazole by Friedel-Crafts reaction to form a closed shape of “?” D-A grid with a yield of 20%.Due to the closure of the “?” structure,the force between the D-A type lattice molecules is reduced,and the charge transfer in the molecule is enhanced.“?” type small molecule in thin film fluorescence emission compared with the solution,blue shift occurs.The HOMO level of the small molecule is similar to that of the non-cyclic H-4FOH molecule,and the LUMO level is smaller,which is beneficial for the hole transportation from the pentacene and is captured by the electret.The memory device prepared by the “?”shape D-A molecule exhibits excellent storage characteristics with a gate voltage of-60 V and a storage window of 40.9 V;Gate voltage is-80 V,storage window is 59.4 V;With a gate Voltage of-100 V,the window is 80.5 V,and does not yet reach the saturation state,the ring of the grid can improve the ability to capture electrons,greatly improving the storage characteristics.