Nonvolatile Polymer Research Articles

Synthesis of angular-shaped naphthodithiophenediimide and its donor–acceptor copolymers as nonvolatile polymer additives for organic solar cells

A new angular-shaped naphthodithiophene diimide (aNDTI) is designed and synthesized. The aNDTI-containing polymers are used as non-volatile additives to improve the efficiency of organic solar cells.

Self-healable, stretchable, and nonvolatile solid polymer electrolytes for sustainable energy storage and sensing applications

Self-healing materials that autonomously recover physical and functional failures have been investigated to improve the operational durability of stretchable and wearable devices. Although various self-healable materials have been reported, imparting self-healability to solid-state nonvolatile polymer electrolytes remains challenging. In this work, highly conductive, stretchable, self-supporting, transparent, and nonvolatile polymer electrolytes, or ionogels, capable of repairing physical and functional damages over 50% in 10 min and full recovery in 1 h without external stimuli were successfully developed using dynamic disulfide metathesis. Self-healable ionogels consisting of a cross-linked tetra-arm polyethylene glycol possessing disulfide linkages and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, were successfully employed in stretchable/self-healable strain sensors and solid-state supercapacitors as piezoresistive components and electrolyte membranes, respectively. Both devices completely recovered their electrical/electrochemical performance even after repetitive cutting/healing cycles. Therefore, these results offer an effective strategy for developing both mechanically and electrically sustainable solid electrolytes for high-performance stretchable and wearable electronic/electrochemical devices.

Approaches to the Sample Preparation of Food Emulsions for Their Efficient Separation and Precipitation of Nonvolatile Polymer Components

Approaches to the Sample Preparation of Food Emulsions for Their Efficient Separation and Precipitation of Nonvolatile Polymer Components

Defect site engineering for charge recombination and stability via polymer surfactant incorporation with an ultra-small amount in perovskite solar cells

A reduction in defect sites that are produced in the process of perovskite crystallization is crucial for efficient perovskite solar cells. In this study, we incorporate an ultra-small amount (less than 0.1 wt%) of a non-volatile polymer additive, poly(ethylene glycol) tridecyl ether (PTE), into the perovskite precursor solution in order to regulate the crystallization kinetics. Even a tiny amount of PTE additives enables effectively to make film surface smooth, suppress charge recombination both between free charge carriers and between trapped and free charge carriers, and improve the electrical stability under continuous illumination. Our findings show that the defects are associated not only with charge recombination but also with electrical stability under illumination. Incorporating PTE additives, charge extraction is facilitated by a reduction in the loss of photogenerated charge carriers, leading to an improvement in photovoltaic efficiency with enhanced stability for the planar p-i-n perovskite solar cells.

Control of Resistive Switching Voltage by Nanoparticle‐Decorated Wrinkle Interface

AbstractControl of resistive switching voltage in nonvolatile memory devices plays a critical role in building commercial ultra‐low power data storage technology. Here, an effective strategy to control the resistive switching voltage in polymer memory devices by interfacial engineering is presented. By creating a wrinkled surface in reduced graphene oxide (rGO) film as the conductive electrode, an electrical bistable phenomenon is observed in polymer diode with this rGO electrode, with the feature of a write‐once‐read‐many‐times nonvolatile memory effect. By further employing silver nanoparticles and controlling their density at the wrinkled rGO electrode/polymer interface, the optimized device exhibits a high performance nonvolatile memory effect with an ultra‐low switching voltage of 0.9 V, high ON/OFF ratio of 1000, and desirable long retention time over 104 s. To the best knowledge, the value of switching voltage is much lower than that of previous related polymer memory devices. This study paves a new way toward ultra‐low power manufacturing of nonvolatile polymer memory devices.

Solution processed nonvolatile polymer transistor memory with discrete distributing molecular semiconductor microdomains as the charge trapping sites

In this work, we demonstrate a polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) based organic thin-film transistor nonvolatile memory, in which the four-layer stacked core architecture is sequentially processed by a method of fully solution spin-coating. The floating-gate layer consists of separated molecular semiconductor 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pen) microdomains distributing in the matrix of polymer poly(styrene) (PS), which is formed by phase-separation during the spin-coating from their blend solution. At the writing/erasing operation, the holes transfer between P3HT active layer and TIPS-Pen microdomains, which results in an prominent memory property, with a memory window of 14 V, memory on/off ratio larger than 350, reliable memory endurance over 500 cycles and a good retention capability over 5000 s with obvious distinguishing reading current at binary 0 and 1 states.

Electrodes: Reduced Graphene Oxide Electrodes with Wrinkled Surface for Nonvolatile Polymer Memory Device Compatibility (Small Methods 7/2018)

Electrodes: Reduced Graphene Oxide Electrodes with Wrinkled Surface for Nonvolatile Polymer Memory Device Compatibility (Small Methods 7/2018)

Reduced Graphene Oxide Electrodes with Wrinkled Surface for Nonvolatile Polymer Memory Device Compatibility

AbstractA general strategy for high performance nonvolatile polymer memory devices, with wrinkled reduced graphene oxide (rGO) films as electrodes and common insulating polymers as active layers, is proposed. The fabricated device exhibits electrical bistability and nonvolatile write‐once‐read‐many times‐type memory, with a low switching voltage of 2.7 V, high ON/OFF ratio of 104 and desirable long retention time over 104 s. The resistive switching of the device might be attributed to carbon‐rich filaments induced by the wrinkled rGO surface. Moreover, this polymer memory device based on a wrinkled rGO electrode can be further applied to flexible data storage systems. The strategy combining such advances in polymer memory devices with simple structure, common materials, excellent reproducibility, and high performance will demonstrate great potential in permanent archival storage applications.

Thermal study of an indium trisguanidinate as a possible indium nitride precursor

Tris-N,N,-dimethyl-N′,N″-diisopropylguanidinatoindium(III) has been investigated both as a chemical vapor deposition precursor and an atomic layer deposition precursor. Although deposition was satisfactory in both cases, each report showed some anomalies in the thermal stability of this compound, warrenting further investigation, which is reported herein. The compound was found to decompose to produce diisopropylcarbodiimide both by computational modeling and solution phase nuclear magnetic resonance characterization. The decomposition was shown to have an onset at approximately 120 °C and had a constant rate of decomposition from 150 to 180 °C. The ultimate decomposition product was suspected to be bisdimethylamido-N,N,-dimethyl-N′,N″-diisopropylguanidinato-indium(III), which appeared to be an intractable, nonvolatile polymer.

New photopatternable polyimide and programmable nonvolatile memory performances

We report the first photopatternable, nonvolatile memory consisting of high-temperature polyimide (PI), poly(hexafluoroisopropylidenediphthalimide-4-cinnamoyloxytri-phenylamine) (6F-HTPA-CI), and we demonstrate the successful fabrication and programmable operation of ‘write-read-erase’ memory devices based on nanoscale thin films of 6F-HTPA-CI. The PI thin film enables scalable fine patternability, providing lines and spaces with excellent pattern fidelity. Isolated individual memory devices were successfully fabricated on a bottom electrode via a sequential process of coating, photopatterning, top electrode deposition, developing, rinsing and drying. The 6F-HTPA-CI cells exhibited excellent nonvolatile memory performances in three different modes (unipolar permanent, unipolar flash and bipolar flash memories), regardless of photo-exposure doses. The switching-ON (writing) voltage was in the range of ±1.5 to ±2.0 V, and the switching-OFF (erasing) voltage was in the range of ±0.3 to ±0.8 V; these voltages are quite low, indicating that power consumption by the devices during operation is low. The ON/OFF current ratio of the devices was in the range of 104–109. Overall, the photopatternable PI 6F-HTPA-CI opens up the possibility of low-cost mass production of high-performance, high-speed, energy-efficient, permanent or rewritable high-density nonvolatile polymer memory devices suitable for future advanced electronics in highly integrated systems.

A Two-Phase Model for Evaporating Solvent-Polymer Mixtures

Evaporating solvent-polymer mixtures play an important role in a number of modern industrial applications. We focus on developing a two-phase model for a fluid composed of a volatile solvent and a nonvolatile polymer in a thin-film geometry. The model accounts for density differences between the phases as well as evaporation at a fluid-air interface. We use the model in one dimension to explore the interplay between evaporation and compositional buoyancy; the former promotes the growth of a polymer-rich skin at the free surface while the latter tends to pull the denser polymeric phase to the substrate. We also examine how these mechanisms influence the drying time of the film. In the limit of dilute polymer, the model can be reduced to a single nonlinear boundary value problem. The nondilute problem has a rich asymptotic structure. We find that the shortest drying times occur in the limit of strong gravitational effects due to the rapid formation of a bilayer with a polymer-rich lower layer and a solvent-rich upper layer. In addition, gravity plays a key role in inhibiting the formation of a skin and can prevent substantial increases in the drying time of the film.

Wafer-Scale Arrays of Nonvolatile Polymer Memories with Microprinted Semiconducting Small Molecule/Polymer Blends

Nonvolatile ferroelectric-gate field-effect transistors (Fe-FETs) memories with solution-processed ferroelectric polymers are of great interest because of their potential for use in low-cost flexible devices. In particular, the development of a process for patterning high-performance semiconducting channel layers with mechanical flexibility is essential not only for proper cell-to-cell isolation but also for arrays of flexible nonvolatile memories. We demonstrate a robust route for printing large-scale micropatterns of solution-processed semiconducting small molecules/insulating polymer blends for high performance arrays of nonvolatile ferroelectric polymer memory. The nonvolatile memory devices are based on top-gate/bottom-contact Fe-FET with ferroelectric polymer insulator and micropatterned semiconducting blend channels. Printed micropatterns of a thin blended semiconducting film were achieved by our selective contact evaporation printing, with which semiconducting small molecules in contact with a micropatterned elastomeric poly(dimethylsiloxane) (PDMS) mold were preferentially evaporated and absorbed into the PDMS mold while insulating polymer remained intact. Well-defined micrometer-scale patterns with various shapes and dimensions were readily developed over a very large area on a 4 in. wafer, allowing for fabrication of large-scale printed arrays of Fe-FETs with highly uniform device performance. We statistically analyzed the memory properties of Fe-FETs, including ON/OFF ratio, operation voltage, retention, and endurance, as a function of the micropattern dimensions of the semiconducting films. Furthermore, roll-up memory arrays were produced by successfully detaching large-area Fe-FETs printed on a flexible substrate with a transient adhesive layer from a hard substrate and subsequently transferring them to a nonplanar surface.

Incorporation of non-conjugated polymer chain in conjugated polymer matrix: A new single step strategy for free standing non-volatile polymer memory

A new single step strategy for polymer memory materials has been explored using free-standing polypyrrole (PPy) film in which non-conjugated polymer chains are incorporated as trap states during synthesis. The PPy film was synthesized by the acidic oxidation of 2,2′:5′,2′′-terpyrrole at the air/water interface. The free-standing PPy films show large hysteresis along with current peaks in opposite directions during current voltage (I–V) characteristics. Hysteric behavior has been utilized to show rewritable memory effect. Furthermore, once electrical state (high or low conduction state) is set, the state is stable for months in ambient condition unless the state is reset by applying a voltage of opposite polarity. Thus the PPy film can be used as read once memory. The memory effect of the film is due to the conformational changes of non-conjugated polymer chains in the PPy matrix. The changes in conformation were confirmed from UV–Vis and FTIR spectra. This new strategy leads free-standing film based all organic polymer memory devices at ultra low cost.

Non-Volatile Polymer Electrolyte Based on Poly(propylene carbonate), Ionic Liquid, and Lithium Perchlorate for Electrochromic Devices

A series of solvent-free ionic liquid (IL)-based polymer electrolytes composed of amorphous and biodegradable poly(propylene carbonate) (PPC) host, LiClO4, and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM(+)BF4(-)) were prepared and characterized for the first time. FTIR studies reveal that the interaction between PPC chains and imidazolium cations weakens the complexation between PPC chains and Li(+) ions. Thermal analysis (DSC and TGA) results show that the incorporation of BMIM(+)BF4(-) into PPC/LiClO4 remarkably decreases the glass transition temperature and improves the thermal stability of the electrolytes. AC impedance results show that the ionic conductivities of the electrolytes are significantly increased with the increase of BMIM(+)BF4(-) amount, the ambient ionic conductivity of the electrolyte at a PPC/LiClO4/BMIM(+)BF4(-) weight ratio of 1/0.2/3 is 1.5 mS/cm, and the ionic transport behavior follows the Arrhenius equation. Both PPC/LiClO4/BMIM(+)BF4(-) and PPC/BMIM(+)BF4(-) electrolytes were applied in electrochromic devices with polyaniline as the electrochromic layer. The PPC/LiClO4/BMIM(+)BF4(-)-based device exhibits much better electrochromic performance in terms of optical contrast and switching time due to the presence of much smaller cations.

Nonvolatile Polymer Memory-Cell Embedded with Ni Nanocrystals Surrounded by NiO in Polystyrene

Nonvolatile Polymer Memory-Cell Embedded with Ni Nanocrystals Surrounded by NiO in Polystyrene

High‐Temperature Operating Non‐volatile Memory of Printable Single‐Wall Carbon Nanotubes Self‐Assembled with a Conjugate Block Copolymer

Printable non-volatile polymer memories are fabricated with solution-processed nanocomposite films of poly(styrene-block-paraphenylene) (PS-b-PPP) and single-wall carbon nanotubes (SWNTs). The devices show stable data retention at high temperatures of up to 100 °C without significant performance degradation due to the strong, non-destructive, and isomorphic π-π interactions between the SWNTs and PPP block.

High‐Performance Non‐Volatile Organic Ferroelectric Memory on Banknotes

High-performance non-volatile polymer ferroelectric memory are fabricated on banknotes using poly(vinylidene fluoride trifluoroethylene). The devices show excellent performance with high remnant polarization, low operating voltages, low leakage, high mobility, and long retention times.

Effect of Glycerol on Retention Time and Electrical Properties of Polymer Bistable Memory Devices Based on Glycerol-Modified PEDOT:PSS

The addition of glycerol to Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonate) (PEDOT:PSS) films affected the bipolar switching characteristics of nonvolatile polymer memory devices (PMDs). Increasing the glycerol/PEDOT:PSS ratio caused increase in the OFF-current of the PMDs, but did not affect the ON-current levels. This result demonstrates that highly-conductive current paths occur in the ON-state. The write-read-erase-read cycle test was operated > 10(5) times. And, the ON-retention time is largely dependent on the glycerol to PEDOT:PSS ratio and annealing temperature. In addition, AFM analysis on the G-PEDOT:PSS films to see how the surface morphology of G-PEDOT:PSS layer influences the retention time properties was carried out.

Kinetically driven self-assembly of a binary solute mixture with controlled phase separation via electro-hydrodynamic flow of corona discharge

This feature article describes a new and facile process to fabricate a variety of thin films of non-volatile binary solute mixtures suitable for high performance organic electronic devices via electro-hydrodynamic flow of conventional corona discharge. Both Corona Discharge Coating (CDC) and a modified version of CDC, Scanning Corona Discharge Coating (SCDC), are based on utilizing directional electric flow, known as corona wind, of the charged uni-polar particles generated by corona discharge between a metallic needle and a bottom plate under a high electric field (5-10 kV cm(-1)). The electric flow rapidly spreads out the binary mixture solution on the bottom plate and subsequently forms a smooth and flat thin film in a large area within a few seconds. In the case of SCDC, the static movement of the bottom electrode on which a binary mixture solution is placed provides further control of thin film formation, giving rise to a film highly uniform over a large area. Interesting phase separation behaviors were observed including nanometer scale phase separation of a polymer-polymer binary mixture and vertical phase separation of a polymer-organic semiconductor mixture. Core-shell type phase separation of either polymer-polymer or polymer-colloidal nanoparticle binary mixtures was also developed with a periodically patterned microstructure when the relative location of the corona wind was controlled to a binary solution droplet on a substrate. We also demonstrate potential applications of thin functional films with controlled microstructures by corona coating to various organic electronic devices such as electroluminescent diodes, field effect transistors and non-volatile polymer memories.

Fabrication of micropatterned ferroelectric gamma poly(vinylidene fluoride) film for non-volatile polymer memory

We describe a facile and robust method for fabricating ferroelectric γ-type poly(vinylidene fluoride) (PVDF) thin films useful for non-volatile polymer memory. Our method is based on heating and cooling rate-independent melt-recrystallization of a thin PVDF film confined under a surface-energy-controlled top layer that strictly forbids paraelectric α crystals. Thin and uniform PVDF films with ferroelectric γ crystals consisting of characteristic twisted lamellae are formed with versatile top layers including metals, oxides, and even polymers. Micropatterns of ferroelectric γ PVDF domains isolated by paraelectric α domains are readily developed when pre-patterned top layers are employed. Our ferroelectric films are conveniently incorporated into arrays of either capacitor or transistor-type non-volatile memory units. Arrays of ferroelectric transistors with vacuum deposited pentacene channels are fabricated with micropatterned γ PVDF films. Furthermore, arrays of bottom-gate ferroelectric transistor memories are demonstrated, in which our ferroelectric PVDF film is directly micropatterned during crystallization under the patterned poly(3-hexyl thiophene) active channels.