Electrically bistable digital memory behaviors of thin films of polyimides based on conjugated bis(triphenylamine) derivatives

Tailoring the Resistive Switching WORM Memory Behavior of Functionalized Bis(triphenylamine)

To better understand the structure-property relationship and the significance of the donor-acceptor (D-A) system in resistive memory devices, a series of new organic small molecules with A-π-D-π-A- and D-π-D-π-D-based architecture comprising a bis(triphenylamine) core unit and ethynyl-linked electron donor/acceptor arms were designed and synthesized. The devices with A-π-D-π-A structures exhibited write-once-read-many memory behavior with a good retention time of 1000 s while those based on D-π-D-π-D molecules presented only conductor property. The compound with nitrophenyl substitution resulted in a higher ON/OFF current ratio of 10⁴, and the fluorophenyl substitution exhibited the lowest threshold voltage of -1.19 V. Solubility of the compounds in common organic solvents suggests that they are promising candidates for economic solution-processable techniques. Density functional theory calculations were used to envision the frontier molecular orbitals and to support the proposed resistive switching mechanisms. It is inferred that the presence of donor/acceptor substituents has a significant impact on the highest occupied molecular orbital-lowest unoccupied molecular orbital energy levels of the molecules, which affects their memory-switching behavior and thus suggests that a D-A architecture is ideal for memory device resistance switching characteristics.

Regulating the electrical resistive switching behaviors of polyimides through different steric hindrance substituents on 2,7-position of tetraphenyl fluorene diamines moieties

Three novel polyimides (PI(TPF-Br BPDA), PI(TPF-Ph BPDA), and PI(TPF-Ph-OMe BPDA)) with tetraphenyl fluorene (TPF) were synthesized and tested. The laboratorial results showed that the constructed electronic devices exhibited different memory behaviors due to the different steric hindrance substituents (bromine atom, phenyl, and 3,5-dimethoxyphenyl) in 2,7-position of TPF molecule. The memorizers based on PI(TPF-Br BPDA) and PI(TPF-Ph BPDA) presented volatile dynamic random access memory (DRAM) feature with turn-on voltages of −2.39 and +1.45 V, as same as −1.71 and +1.74 V, separately. However, the PI(TPF-Ph-OMe BPDA) based apparatus exhibited non-volatile write-once read-many-times memory (WORM) behavior with turn-on voltage of −1.13 V, due to the more charge traps of 3,5-dimethoxyphenyl moieties and higher dipole moment. The switching mechanism was verified by quantum simulation of energy level, electrostatic potential (ESP) surface and dipole moment. These results indicated that the electrical memory performance of the synthesized TPF-based PIs could be adjusted by modifying the electron donor structure.

Highly efficient polymerization via sulfur(vi)-fluoride exchange (SuFEx): novel polysulfates bearing a pyrazoline–naphthylamide conjugated moiety and their electrical memory performance

Two polysulfates (PolyTPP-NI and CPTPP-NI) were synthesized by a SuFEx click reaction, and their memory devices show Flash behaviors.

Synthesis and optical and electrochemical memory properties of fluorene–triphenylamine alternating copolymer

A fluorene–triphenylamine copolymer (PF–TPA) was designed and synthesized under Suzuki coupling reaction conditions in this work. It exhibited a typical electrical conductance switching behavior and non-volatile flash memory effects.

Novel solution-processable functional polyimide/ZrO2 hybrids with tunable digital memory behaviors

The resulting PI hybrid films exhibited electrically programmable digital memory properties from DRAM, SRAM to WORM with a high ON/OFF current ratio by controlling the content of ZrO₂ from 0 to 30 wt%.

Electrically bistable and non-volatile memory devices based on p-toluenesulfonic-doped poly(triphenylamine)

The devices are bi-directionally switchable and have non-volatile WORM memory characteristics. They were used as promising candidates in security and data protection applications.

Linkage and donor–acceptor effects on resistive switching memory devices of 4-(N-carbazolyl)triphenylamine-based polymers

In order to gain deeper insight about the linkage effect and donor–acceptor effect on memory behavior (from DRAM to WORM), 4-(N-carbazolyl)triphenylamine-based polyimides and polyamides were synthesized and their memory behaviours were investigated.

Ultra-flexible nonvolatile memory based on donor-acceptor diketopyrrolopyrrole polymer blends

Flexible memory cell array based on high mobility donor-acceptor diketopyrrolopyrrole polymer has been demonstrated. The memory cell exhibits low read voltage, high cell-to-cell uniformity and good mechanical flexibility, and has reliable retention and endurance memory performance. The electrical properties of the memory devices are systematically investigated and modeled. Our results suggest that the polymer blends provide an important step towards high-density flexible nonvolatile memory devices.

Self-assembly of novel lipid-mimicking brush polymers in nanoscale thin films

A series of well-defined poly(oxy(11-phosphorylcholineundecylthiomethyl)ethylene-ran-oxy(n-dodecylthiomethyl)ethylene) (PECH-PCm: m = 0-100 mol% phosphorylcholine (PC)) polymers were used to prepare nanoscale thin films that were characterized by synchrotron X-ray reflectivity (XR) analysis. The quantitative XR analysis provided structural insights into the PECH-PCm thin films. The PECH-PC0 polymer film formed a well-ordered in-plane oriented molecular multibilayer structure, whose individual layers consisted of two sublayers. One sublayer was composed of the fully extended backbones and inner part of the bristles, exhibiting a relatively low electron density, whereas the other sublayer was composed of a bilayer of the outer parts of the bristles without interdigitation. The PECH-PC100 polymer film also formed a well-ordered in-plane oriented molecular multibilayer structure, the individual layers of which were composed of four sublayers rather than two. The bristles in the layer were interdigitated in part via the zwitterionic interactions of the PC end groups. Surprisingly, regardless of the copolymer composition, the PECH-PCm random copolymer molecules in the thin films self-assembled to form a multilayered structure that resembled the structure formed by the PECH-PC100 polymer. These properties have not been observed in other conventional random brush copolymer films. The remarkable multibilayer structures originated from the zwitterionic PC end groups and their favorable interactions and interdigitated structures, which overcame any negative contributions caused by the heterogeneity of the bristles. The unique self-assembly properties of the PECH-PCm polymers always provide a PC-rich surface. The PECH-PCm random copolymers successfully mimicked the molecular bilayer structures formed by natural lipids.

Linkage effect on the memory behavior of sulfonyl-containing aromatic polyether, polyester, polyamide, and polyimide

Sulfonyl-containing aromatic polymers DSPE, DSPET, DSPA, and DSPI consisting of a triphenylamine moiety were synthesized and the memory behavior was investigated. By choosing the suitable linkage between the electron donor and acceptor, tunable memory properties (from insulator to different retention time SRAM) could be achieved.