High‐Performance Ferroelectric Memory Based on Phase‐Separated Films of Polymer Blends

High‐performance polymer memory is fabricated using blends of ferroelectric poly(vinylidene‐fluoride‐trifluoroethylene) (P(VDF‐TrFE)) and highly insulating poly(p‐phenylene oxide) (PPO). The blend films spontaneously phase separate into amorphous PPO nanospheres embedded in a semicrystalline P(VDF‐TrFE) matrix. Using low molecular weight PPO with high miscibility in a common solvent, i.e., methyl ethyl ketone, blend films are spin cast with extremely low roughness (R_rms ≈ 4.92 nm) and achieve nanoscale phase seperation (PPO domain size < 200 nm). These blend devices display highly improved ferroelectric and dielectric performance with low dielectric losses (<0.2 up to 1 MHz), enhanced thermal stability (up to ≈353 K), excellent fatigue endurance (80% retention after 10⁶ cycles at 1 KHz) and high dielectric breakdown fields (≈360 MV/m).     

High Performance Multi‐Level Non‐Volatile Polymer Memory with Solution‐Blended Ferroelectric Polymer/High‐k Insulators for Low Voltage Operation

Polymer ferroelectric‐gate field effect transistors (Fe‐FETs) employing ferroelectric polymer thin films as gate insulators are highly attractive as a next‐generation non‐volatile memory. Furthermore, polymer Fe‐FETs have been recently of interest owing to their capability of storing data in more than 2 states in a single device, that is, they have multi‐level cell (MLC) operation potential for high density data storage. However, among a variety of technological issues of MLC polymer Fe‐FETs, the requirement of high voltage for cell operation is one of the most urgent problems. Here, a low voltage operating MLC polymer Fe‐FET memory with a high dielectric constant (k) ferroelectric polymer insulator is presented. Effective enhancement of capacitance of the ferroelectric gate insulator layer is achieved by a simple binary solution‐blend of a ferroelectric poly(vinylidene fluoride‐co‐trifluoroethylene) (PVDF‐TrFE) (k ≈ 8) with a relaxer high‐k poly(vinylidene‐fluoride–trifluoroethylene–chlorotrifluoroethylene) (PVDF‐TrFE‐CTFE) (k ≈ 18). At optimized conditions, a ferroelectric insulator with a PVDF‐TrFE/PVDF‐TrFE‐CTFE (10/5) blend composition enables the discrete six‐level multi‐state operation of a MLC Fe‐FET at a gate voltage sweep of ±18 V with excellent data retention and endurance of each state of more than 10⁴ s and 120 cycles, respectively.     

Semitransparent,Flexible, and Self‐Powered Photodetectors Based on Ferroelectricity‐Assisted Perovskite Nanowire Arrays

Transparent and flexible photodetectors hold great promise in next‐generation portable and wearable optoelectronic devices. However, most of the previously reported devices need an external energy power source to drive its operation or require complex fabrication processes. Herein, designed is a semitransparent, flexible, and self‐powered photodetector based on the integrated ferroelectric poly(vinylidene‐fluoride‐trifluoroethylene) (P(VDF‐TrFE)) and perovskite nanowire arrays on the flexible polyethylene naphthalate substrate via a facile imprinting method. Through optimizing the treatment conditions, including polarization voltage, polarization time, and the concentration of P(VDF‐TrFE), the resulting device exhibits remarkable detectivity (7.3 × 10¹² Jones), fast response time (88/154 µs) at zero bias, as well as outstanding mechanical stability. The excellent performance is attributed to the efficient charge separation and transport originating from the highly oriented 1D transport pathway and the polarization‐induced internal electric field within P(VDF‐TrFE)/perovskite hybrid nanowire arrays.     

Control of Current Hysteresis of Networked Single‐Walled Carbon Nanotube Transistors by a Ferroelectric Polymer Gate Insulator

Films made of 2D networks of single‐walled carbon nanotubes (SWNTs) are one of the most promising active‐channel materials for field‐effect transistors (FETs) and have a variety of flexible electronic applications, ranging from biological and chemical sensors to high‐speed switching devices. Challenges, however, still remain due to the current hysteresis of SWNT‐containing FETs, which has hindered further development. A new and robust method to control the current hysteresis of a SWNT‐network FET is presented, which involves the non‐volatile polarization of a ferroelectric poly(vinylidene fluoride‐trifluoroethylene) (P(VDF‐TrFE)) gate insulator. A top‐gate FET with a solution‐processed SWNT‐network exhibits significant suppression of the hysteresis when the gate‐voltage sweep is greater than the coercive field of the ferroelectric polymer layer (≈50 MV m^?1). These near‐hysteresis‐free characteristics are believed to be due to the characteristic hysteresis of the P(VDF‐TrFE), resulting from its non‐volatile polarization, which makes effective compensation for the current hysteresis of the SWNT‐network FETs. The onset voltage for hysteresis‐minimized operation is able to be tuned simply by controlling the thickness of the ferroelectric film, which opens the possibility of operating hysteresis‐free devices with gate voltages down to a few volts.     

Non‐volatile Ferroelectric Poly(vinylidene fluoride‐co‐trifluoroethylene) Memory Based on a Single‐Crystalline Tri‐isopropylsilylethynyl Pentacene Field‐Effect Transistor

A new type of nonvolatile ferroelectric poly(vinylidene fluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)) memory based on an organic thin‐film transistor (OTFT) with a single crystal of tri‐isopropylsilylethynyl pentacene (TIPS‐PEN) as the active layer is developed. A bottom‐gate OTFT is fabricated with a thin P(VDF‐TrFE) film gate insulator on which a one‐dimensional ribbon‐type TIPS‐PEN single crystal, grown via a solvent‐exchange method, is positioned between the Au source and drain electrodes. Post‐thermal treatment optimizes the interface between the flat, single‐crystalline ab plane of TIPS‐PEN and the polycrystalline P(VDF‐TrFE) surface with characteristic needle‐like crystalline lamellae. As a consequence, the memory device exhibits a substantially stable source–drain current modulation with an ON/OFF ratio hysteresis greater than 10³, which is superior to a ferroelectric P(VDF‐TrFE) OTFT that has a vacuum‐evaporated pentacene layer. Data retention longer than 5 × 10⁴ s is additionally achieved in ambient conditions by incorporating an interlayer between the gate electrode and P(VDF‐TrFE) thin film. The device is environmentally stable for more than 40 days without additional passivation. The deposition of a seed solution of TIPS‐PEN on the chemically micropatterned surface allows fabrication arrays of TIPS‐PEN single crystals that can be potentially useful for integrated arrays of ferroelectric polymeric TFT memory.     

Micropatterned P(VDF‐TrFE) Film‐Based Piezoelectric Nanogenerators for Highly Sensitive Self‐Powered Pressure Sensors

Here micropatterned poly(vinylidenefluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)) films‐based piezoelectric nanogenerators (PNGs) with high power‐generating performance for highly sensitive self‐powered pressure sensors are demonstrated. The microstructured P(VDF‐TrFE)‐based PNGs reveal nearly five times larger power output compared to a flat film‐based PNG. The micropatterning of P(VDF‐TrFE) polymer makes itself ultrasensitive in response to mechanical deformation. The application is demonstrated successfully as self‐powered pressure sensors in which mechanical energy comes from water droplet and wind. The mechanism of the high performance is intensively discussed and illustrated in terms of strain developed in the flat and micropatterned P(VDF‐TrFE) films. The impact derived from the patterning on the output performance is studied in term of effective pressure using COMSOL multiphysics software.     

Printed,Flexible, Organic Nano‐Floating‐Gate Memory: Effects of Metal Nanoparticles and Blocking Dielectrics on Memory Characteristics

The effects of using a blocking dielectric layer and metal nanoparticles (NPs) as charge‐trapping sites on the characteristics of organic nano‐floating‐gate memory (NFGM) devices are investigated. High‐performance NFGM devices are fabricated using the n‐type polymer semiconductor, poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2)), and various metal NPs. These NPs are embedded within bilayers of various polymer dielectrics (polystyrene (PS)/poly(4‐vinyl phenol) (PVP) and PS/poly(methyl methacrylate) (PMMA)). The P(NDI2OD‐T2) organic field‐effect transistor (OFET)‐based NFGM devices exhibit high electron mobilities (0.4–0.5 cm² V^?1 s^?1) and reliable non‐volatile memory characteristics, which include a wide memory window (≈52 V), a high on/off‐current ratio (I_on/I_off ≈ 10⁵), and a long extrapolated retention time (>10⁷ s), depending on the choice of the blocking dielectric (PVP or PMMA) and the metal (Au, Ag, Cu, or Al) NPs. The best memory characteristics are achieved in the ones fabricated using PMMA and Au or Ag NPs. The NFGM devices with PMMA and spatially well‐distributed Cu NPs show quasi‐permanent retention characteristics. An inkjet‐printed flexible P(NDI2OD‐T2) 256‐bit transistor memory array (16 × 16 transistors) with Au‐NPs on a polyethylene naphthalate substrate is also fabricated. These memory devices in array exhibit a high I_on/I_off (≈10^{4 ± 0.85}), wide memory window (≈43.5 V ± 8.3 V), and a high degree of reliability.     

A High‐k Fluorinated P(VDF‐TrFE)‐g‐PMMA Gate Dielectric for High‐Performance Flexible Field‐Effect Transistors

A newly synthesized high‐k polymeric insulator for use as gate dielectric layer for organic field‐effect transistors (OFETs) obtained by grafting poly(methyl methacrylate) (PMMA) in poly(vinylidene fluoride‐trifluoroethylene) (P(VDF‐TrFE)) via atom transfer radical polymerization transfer is reported. This material design concept intents to tune the electrical properties of the gate insulating layer (capacitance, leakage current, breakdown voltage, and operational stability) of the high‐k fluorinated polymer dielectric without a large increase in operating voltage by incorporating an amorphous PMMA as an insulator. By controlling the grafted PMMA percentage, an optimized P(VDF‐TrFE)‐g‐PMMA with 7 mol% grafted PMMA showing reasonably high capacitance (23–30 nF cm^?2) with low voltage operation and negligible current hysteresis is achieved. High‐performance low‐voltage‐operated top‐gate/bottom‐contact OFETs with widely used high mobility polymer semiconductors, poly[[2,5‐bis(2‐octyldodecyl)‐2,3,5,6‐tetrahydro‐3,6‐dioxopyrrolo [3,4‐c]pyrrole‐1,4‐diyl]‐alt‐[[2,2′‐(2,5‐thiophene)bis‐thieno(3,2‐b)thiophene]‐5,5′‐diyl]] (DPPT‐TT), and poly([N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)) are demonstrated here. DPPT‐TT OFETs with P(VDF‐TrFE)‐g‐PMMA gate dielectrics exhibit a reasonably high field‐effect mobility of over 1 cm² V^?1 s^?1 with excellent operational stability.     

Ultrahigh‐Performance Flexible and Self‐Powered Photodetectors with Ferroelectric P(VDF‐TrFE)/Perovskite Bulk Heterojunction

Flexible and self‐powered perovskite photodetectors attract widespread research interests due to their potential applications in portable and wearable optoelectronic devices. However, the reported devices mainly adopt an independent layered structure with complex fabrication processes and high carrier recombination. Herein, an integrated ferroelectric poly(vinylidene‐fluoride‐trifluoroethylene) (P(VDF‐TrFE)) and perovskite bulk heterojunction film photodetector on the polyethylene naphthalate substrate is demonstrated. Under the optimum treatment conditions (the polarization voltage and time, and the concentration of P(VDF‐TrFE)), the photodetector exhibits a largely enhanced performance compared to the pristine perovskite device. The resulting device exhibits ultrahigh performance with a large detectivity (1.4 × 10¹³ Jones) and fast response time (92/193 µs) at the wavelength of 650 nm. The improved performance is attributed to the fact that the polarized P(VDF‐TrFE)/perovskite hybrid film provides a stronger built‐in electric field to facilitate the separation and transportation of photogenerated carriers. These findings provide a new route to design self‐powered photodetectors from the aspect of device structure and carrier transport.     

Confined Ferroelectric Properties in Poly(Vinylidene Fluoride‐co‐Chlorotrifluoroethylene)‐graft‐Polystyrene Graft Copolymers for Electric Energy Storage Applications

Dielectric polymer film capacitors having high energy density, low loss and fast discharge speed are highly desirable for compact and reliable electrical power systems. In this work, we study the confined ferroelectric properties in a series of poly(vinylidene fluoride‐co‐chlorotrifluoroethylene)‐graft‐polystyrene [P(VDF‐CTFE)‐g‐PS] graft copolymers, and their potential application as high energy density and low loss capacitor films. Thin films (ca. 20 μm) are prepared by different processing methods, namely, hot‐pressing or solution‐casting followed by mechanical stretching at elevated temperatures. After crystallization‐induced microphase separation, PS side chains are segregated to the periphery of PVDF crystals, forming a confining interfacial layer. Due to the low polarizability of this confining PS‐rich layer at the amorphous–crystalline interface, the compensation polarization is substantially decreased resulting in a novel confined ferroelectric behavior in these graft copolymers. Both dielectric and ferroelectric losses are significantly reduced at the expense of a moderate decrease in discharged energy density. Our study indicates that the best performance is achieved for a P(VDF‐CTFE)‐g‐PS graft copolymer with 34 wt‐% PS; a relatively high discharged energy density of approximately 10 J cm^?3 at 600 MV m^?1, a low dielectric loss (tanδ = 0.006 at 1 kHz), and a low hysteresis loop loss (17.6%) at 550 MV m^?1.     

Sustainable Nanotextured Wave Energy Harvester Based on Ferroelectric Fatigue‐Free and Flexoelectricity‐Enhanced Piezoelectric P(VDF‐TrFE) Nanofibers with BaSrTiO3 Nanoparticles

Here, ultrathin, flexible, and sustainable nanofiber‐based piezoelectric nanogenerators (NF‐PENGs) are fabricated and applied as wave energy harvesters. The NF‐PENGs are composed of poly(vinylidene fluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)) nanofibers with embedded barium strontium titanate (BaSrTiO₃) nanoparticles, which are fabricated by using facile, scalable, and cost‐effective fiber‐forming methods, including electrospinning and solution blowing. The inclusion of ferroelectric BaSrTiO₃ nanoparticles inside the electrospun P(VDF‐TrFE) nanofibers enhances the sustainability of the NF‐PENGs and results in unique flexoelectricity‐enhanced piezoelectric nanofibers. Not only do these NF‐PENGs yield a superior performance compared to the previously reported NF‐PENGs, but they also exhibit an outstanding durability in terms of mechanical properties and cyclability. Furthermore, a new theoretical estimate of the energy harvesting efficiency from the water waves is introduced here, which can also be employed in future studies associated with various nanogenerators, including PENGs and triboelectric nanogenerators.     

High‐Performance Top‐Gated Organic Field‐Effect Transistor Memory using Electrets for Monolithic Printed Flexible NAND Flash Memory

High‐performance top‐gated organic field‐effect transistor (OFET) memory devices using electrets and their applications to flexible printed organic NAND flash are reported. The OFETs based on an inkjet‐printed p‐type polymer semiconductor with efficiently chargeable dielectric poly(2‐vinylnaphthalene) (PVN) and high‐k blocking gate dielectric poly(vinylidenefluoride‐trifluoroethylene) (P(VDF‐TrFE)) shows excellent non‐volatile memory characteristics. The superior memory characteristics originate mainly from reversible charge trapping and detrapping in the PVN electret layer efficiently in low‐k/high‐k bilayered dielectrics. A strategy is devised for the successful development of monolithically inkjet‐printed flexible organic NAND flash memory through the proper selection of the polymer electrets (PVN or PS), where PVN/‐ and PS/P(VDF‐TrFE) devices are used as non‐volatile memory cells and ground‐ and bit‐line select transistors, respectively. Electrical simulations reveal that the flexible printed organic NAND flash can be possible to program, read, and erase all memory cells in the memory array repeatedly without affecting the non‐selected memory cells.     

Multiferroic Polymer Laminate Composites Exhibiting High Magnetoelectric Response Induced by Hydrogen‐Bonding Interactions

The coupling of the magnetic, electric, and elastic properties in multiferroics creates new collective phenomena and enables next‐generation device paradigms. In this work, the hydrogen bonding interaction between hydrate salts and ferroelectric polymers is exploited in the development of high‐performance magnetoelectric (ME) polymer laminate composites. The microstructures and crystallite structures of the Al(NO₃)₃·9H₂O doped poly(vinylidene fluoride‐co‐hexafluoropropylene), P(VDF‐HFP), are carefully studied. The effect of hydrogen bonding interaction on the polarization ordering of the ferroelectric polymers is investigated by 2D wide‐angle X‐ray diffraction, polarized Fourier transform infrared spectra, and dielectric spectra at varied frequencies and temperatures. It is found that hydrogen bond not only promotes the formation of the polar crystallite phase but also improves the polarization ordering in the ferroelectric polymer, which subsequently increases the remnant polarization of the polymers as verified in the polarization‐electric field loop measurements. These entail marked improvement in the ME voltage coefficients (α_ME) of the resulting polymer laminate composites based on ferromagnetic Metglas relative to analogous composites. The composite exhibits a state‐of‐the‐art α_ME value of 20 V cm^‐1 Oe under a dc magnetic field of ≈4 Oe and a colossal α_ME of 320 V cm^‐1 Oe at a frequency of 68 kHz.     

Electrode Dependence of Tunneling Electroresistance and Switching Stability in Organic Ferroelectric P(VDF‐TrFE)‐Based Tunnel Junctions

Ferroelectric tunnel junctions (FTJs) are promising candidates for nonvolatile memories and memristor‐based computing circuits. Thus far, most research has focused on FTJs with a perovskite oxide ferroelectric tunnel barrier. As the need for high‐temperature epitaxial film growth challenges the technological application of such inorganic junctions, more easily processable organic ferroelectrics can serve as alternative if large tunneling electroresistance (TER) and good switching durability would persist. This study reports on the performance of FTJs with a spin‐coated ferroelectric P(VDF‐TrFE) copolymer tunnel barrier. The use of three different bottom electrodes, indium tin oxide (ITO), La_0.67Sr_0.33MnO₃, (LSMO), and Nb‐doped SrTiO₃ (STO) are compared and it is shown that the polarity and magnitude of the TER effect depend on their conductivity. The largest TER of up to 10⁷% at room temperature is measured on FTJs with a semiconducting Nb‐doped STO electrode. This large switching effect is attributed to the formation of an extra barrier over the space charge region in the substrate. The organic FTJs exhibit good resistance retention and switching endurance up to 380 K, which is just below the ferroelectric Curie temperature of the P(VDF‐TrFE) barrier.     

Processing and Low Voltage Switching of Organic Ferroelectric Phase‐Separated Bistable Diodes

The processing of solution‐based binary blends of the ferroelectric random copolymer poly(vinylidene fluoride‐trifluoroethylene) P(VDF‐TrFE) and the semiconducting polymer poly(9,9‐dioctylfluorenyl‐2,7‐diyl) (PFO) applied by spin‐coating and wire‐bar coating is investigated. By systematic variation of blend composition, solvent, and deposition temperature it is shown that much smoother blend films can be obtained than reported thus far. At a low PFO:P(VDF‐TrFE) ratio the blend film consists of disk‐shaped PFO domains embedded in a P(VDF‐TrFE) matrix, while an inverted structure is obtained in case the P(VDF‐TrFE) is the minority component. The microstructure of the phase separated blend films is self‐affine. From this observation and from the domain size distribution it is concluded that the phase separation occurs via spinodal decomposition, irrespectively of blend ratio. This is explained by the strong incompatibility of the two polymers expressed by the binary phase diagram, as constructed from thermal analysis data. Time resolved numerical simulation of the microstructure evolution during de‐mixing qualitatively shows how an elevated deposition temperature has a smoothening effect as a result of the reduction of the repulsion between the blend components. The small roughness allowed the realization of bistable rectifying diodes that switch at low voltages with a yield of 100%. This indicates that memory characteristics can be tailored from the outset while processing parameters can be adjusted according to the phase behavior of the active components.     

A Giant Electrocaloric Effect in Nanoscale Antiferroelectric and Ferroelectric Phases Coexisting in a Relaxor Pb0.8Ba0.2ZrO3 Thin Film at Room Temperature

Recently, large electrocaloric effects (ECE) in antiferroelectric sol‐gel PbZr_0.95Ti_0.05O₃ thin films and in ferroelectric polymer P(VDF‐TrFE)55/45 thin films were observed near the ferroelectric Curie temperatures of these materials (495 K and 353 K, respectively). Here a giant ECE (ΔT = 45.3 K and ΔS = 46.9 J K^?1 kg^?1 at 598 kV cm^?1) is obtained in relaxor ferroelectric Pb_0.8Ba_0.2ZrO₃ (PBZ) thin films fabricated on Pt(111)/TiO_x/SiO₂/Si substrates using a sol‐gel method. Nanoscale antiferroelectric (AFE) and ferroelectric (FE) phases coexist at room temperature (290 K) rather than at the Curie temperature (408 K) of the material. The giant ECE in such a system is attributed to the coexistence of AFE and FE phases and a field‐induced nanoscale AFE to FE phase transition. The giant ECE of the thin film makes this a promising material for applications in cooling systems near room temperature.     

Nanoscale Morphology of Conjugated Polymer/Fullerene‐Based Bulk‐ Heterojunction Solar Cells

The relation between the nanoscale morphology and associated device properties in conjugated polymer/fullerene bulk‐heterojunction “plastic solar cells” is investigated. We perform complementary measurements on solid‐state blends of poly[2‐methoxy‐5‐(3,7‐dimethyloctyloxy)]‐1,4‐phenylenevinylene (MDMO‐PPV) and the soluble fullerene C₆₀ derivative 1‐(3‐methoxycarbonyl) propyl‐1‐phenyl [6,6]C₆₁ (PCBM), spin‐cast from either toluene or chlorobenzene solutions. The characterization of the nanomorphology is carried out via scanning electron microscopy (SEM) and atomic force microscopy (AFM), while solar‐cell devices were characterized by means of current–voltage (I–V) and spectral photocurrent measurements. In addition, the morphology is manipulated via annealing, to increase the extent of phase separation in the thin‐film blends and to identify the distribution of materials. Photoluminescence measurements confirm the demixing of the materials under thermal treatment. Furthermore the photoluminescence of PCBM clusters with sizes of up to a few hundred nanometers indicates a photocurrent loss in films of the coarser phase‐separated blends cast from toluene. For toluene‐cast films the scale of phase separation depends strongly on the ratio of MDMO‐PPV to PCBM, as well as on the total concentration of the casting solution. Finally we observe small beads of 20–30 nm diameter, attributed to MDMO‐PPV, in blend films cast from both toluene and chlorobenzene.     

Formation of a Ground‐State Charge‐Transfer Complex in Polyfluorene//[6,6]‐Phenyl‐C61 Butyric Acid Methyl Ester (PCBM) Blend Films and Its Role in the Function of Polymer/PCBM Solar Cells

Evidence is presented for the formation of a weak ground‐state charge‐transfer complex in the blend films of poly[9,9‐dioctylfluorene‐co‐N‐(4‐methoxyphenyl)diphenylamine] polymer (TFMO) and [6,6]‐phenyl‐C₆₁ butyric acid methyl ester (PCBM), using photothermal deflection spectroscopy (PDS) and photoluminescence (PL) spectroscopy. Comparison of this polymer blend with other polyfluorene polymer/PCBM blends shows that the appearance of this ground‐state charge‐transfer complex is correlated to the ionization potential of the polymer, but not to the optical gap of the polymer or the surface morphology of the blend film. Moreover, the polymer/PCBM blend films in which this charge‐transfer complex is observed also exhibit efficient photocurrent generation in photovoltaic devices, suggesting that the charge‐transfer complex may be involved in charge separation. Possible mechanisms for this charge‐transfer state formation are discussed as well as the significance of this finding to the understanding and optimization of polymer blend solar cells.     

High‐Performance Piezoelectric,Pyroelectric, and Triboelectric Nanogenerators Based on P(VDF‐TrFE) with Controlled Crystallinity and Dipole Alignment

Poly(vinylidenefluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)), as a ferroelectric polymer, offers great promise for energy harvesting for flexible and wearable applications. Here, this paper shows that the choice of solvent used to dissolve the polymer significantly influences its properties in terms of energy harvesting. Indeed, the P(VDF‐TrFE) prepared using a high dipole moment solvent has higher piezoelectric and pyroelectric coefficients and triboelectric property. Such improvements are the result of higher crystallinity and better dipole alignment of the polymer prepared using a higher dipole moment solvent. Finite element method simulations confirm that the higher dipole moment results in higher piezoelectric, pyroelectric, and triboelectric potential distributions. Furthermore, P(VDF‐TrFE)‐based piezoelectric, pyroelectric, and triboelectric nanogenerators (NGs) experimentally validate that the higher dipole moment solvent significantly enhances the power output performance of the NGs; the improvement is about 24% and 82% in output voltage and current, respectively, for piezoelectric NG; about 40% and 35% in output voltage and current, respectively, for pyroelectric NG; and about 65% and 75% in output voltage and current for triboelectric NG. In brief, the approach of using a high dipole moment solvent is very promising for high output P(VDF‐TrFE)‐based wearable NGs.     

Low‐Power Nonvolatile Charge Storage Memory Based on MoS2 and an Ultrathin Polymer Tunneling Dielectric

Low‐power, nonvolatile memory is an essential electronic component to store and process the unprecedented data flood arising from the oncoming Internet of Things era. Molybdenum disulfide (MoS₂) is a 2D material that is increasingly regarded as a promising semiconductor material in electronic device applications because of its unique physical characteristics. However, dielectric formation of an ultrathin low‐k tunneling on the dangling bond‐free surface of MoS₂ is a challenging task. Here, MoS₂‐based low‐power nonvolatile charge storage memory devices are reported with a poly(1,3,5‐trimethyl‐1,3,5‐trivinyl cyclotrisiloxane) (pV3D3) tunneling dielectric layer formed via a solvent‐free initiated chemical vapor deposition (iCVD) process. The surface‐growing polymerization and low‐temperature nature of the iCVD process enable the conformal growing of low‐k (≈2.2) pV3D3 insulating films on MoS₂. The fabricated memory devices exhibit a tunable memory window with high on/off ratio (≈10⁶), excellent retention times of 10⁵ s with an extrapolated time of possibly years, and an excellent cycling endurance of more than 10³ cycles, which are much higher than those reported previously for MoS₂‐based memory devices. By leveraging the inherent flexibility of both MoS₂ and polymer dielectric films, this research presents an important milestone in the development of low‐power flexible nonvolatile memory devices.