| With the rapid development of modern science and technology, people’s demand forinformation has increased dramatically, and will continue to increase for the years to come.However, the development of traditional data-storage devices based on optical andmagnetic techniques remain stagnant with the optimized capacity of traditionaldata-storage devices being about106Bit/cm2. Hence, it is imperative that we should makea great breakthrough in the field of data-storage technology. It was not until2010that ourgroup successfully designed a device based on a V-style small molecule containing azomoieties, which was indeed a landmark from traditional binary data-storage performance topromising ternary data-storage performance, thus data-storage capacity per unit has beenlargely elevated.In this paper, a new electron-withdrawing group (trap), benzothiazole, has beenintroduced to the backbone of a series of organic small molecules instead of azo groupwhich has been widely studied in our group. Combined with other electron acceptors ofdifferent electron-withdrawing abilities, we studied the influence of different “traps” on thedata-storage performance of devices. Meanwhile, this paper also has a systemic study onfilm-making technologies which also play an important role in enhancing the performanceof devices.(1) Two small conjugated molecules BTVCz-NO2and BTVCz, each incorporatingan electron-donating carbazole group and a medium electron-withdrawing benzothiazolegroup, were both successfully designed and synthesized. Molecule BTVCz-NO2is anA1-D-A2structure while BTVCz is a single D-A structure. And the fabricated device withBTVCz-NO2as active material showed non-volatile ternary WORM data-storage behavior,whereas its “counterpart” device with BTVCz as active material exhibited volatile binaryDRAM data-storage behaviors. The two films differentiated over their optical,electrochemical and morphological properties. Combined with theoretical calculation ofeach molecule, we conclude that different data-storage behaviors can be achieved by introducing different electron acceptors. This study has great significance for design ofmore superior high-density data storage devices by adjusting molecule structures.(2) Molecule BTVCz-NO2was fabricated into films with two different film-formingtechniques, spin-coating and vacuum deposition. Both devices showed nonvolatile ternaryWORM data-storage behavior. However, the spin-coated device had lower switchingthreshold voltages and the switching probability of the device was much higher than thevacuum-deposited device. Through a thorough study of their optical, electrochemical andmorphological properties, we found that the spin-coated films tended to have greater redshifts in their UV spectra, smoother surfaces with smaller roughness, and denser stacking(d-spacing) than the vacuum-deposited films. Therefore, different film-making methodsalso have an important effect on the data-storage performances of devices, through whichfilms of the best quality can be screened.(3) An organic small molecule, DPP-BT, in which an electron-deficientdiketopyrrolopyrrole (DPP) unit with two long alkyl chains is flanked by twobenzothiazole groups, has been successfully designed and synthesized. The indium-tinoxide (ITO)/Small-molecule/Al sandwich structures were fabricated by using varioussolvents such as pure chlorobenzene (CB), pure cyclohexanone (CH) and mixed solvents(CH/CB) with different ratios. The influences of mixed solvents on the data-storageperformances have been investigated. The results show that the device spin-coated by amixed solvent of CH: CB=1:2can achieve ternary nonvolatile data-storage behavior withits switching threshold voltage at-1.3V and-2.3V, which is lower than any other devicesfabricated by other solvents. What’s more, the switching probability of the device was40out of64cells (device yield of62%), which is also far higher than other devices. |
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