Organic Ferroelectric Materials and Applications aims to bring an up-to date account of the field with discussion of recent findings. This book presents an interdisciplinary resource for scientists from both academia and industry on the science and applications of molecular organic piezo- and ferroelectric materials. The book addresses the fundamental science of ferroelectric polymers, molecular crystals, supramolecular networks, and other key and emerging organic materials systems. It touches on important processing and characterization methods and provides an overview of current and emerging applications of organic piezoelectrics and ferroelectrics for electronics, sensors, energy harvesting, and biomedical technologies. Organic Ferroelectric Materials and Applications will be of special interest to those in academia or industry working in materials science, engineering, chemistry, and physics. Provides an overview of key physical properties of the emerging piezoelectric and ferroelectric molecular and supramolecular systems Discusses best practices of processing, patterning, and characterization methods and techniques Addresses current and emerging applications for electronics, materials development, sensors, energy harvesting, and biomedical technologies
This book presents the basic physical properties, structure, fabrication methods and applications of ferroelectric materials. These are widely used in various devices, such as piezoelectric/electrostrictive transducers and actuators, pyroelectric infrared detectors, optical integrated circuits, optical data storage, display devices, etc. The ferroelectric materials described in this book include a relatively complete list of practical and promising ferroelectric single crystals, bulk ceramics and thin films. Included are perovskite-type, lithium niobate, tungsten-bronze-type, water-soluable crystals and other inorganic materials, as well as organic ferroelectrics (polymers, liquid crystals, and composites). Basic concepts, principles and methods for the physical property characteristics of ferroelectric materials are introduced in the first two chapters for those readers new to the subject of ferroelectricity. Not only professional researchers and engineers but also students and other readers who have limited physical knowledge and an interest in ferroelectrics, will welcome this book.
Provides a comprehensive overview of the emerging applications of ferroelectric materials in energy harvesting and storage Conventional ferroelectric materials are normally used in sensors and actuators, memory devices, and field effect transistors, etc. Recent progress in this area showed that ferroelectric materials can harvest energy from multiple sources including mechanical energy, thermal fluctuations, and light. This book gives a complete summary of the novel energy-related applications of ferroelectric materials?and reviews both the recent advances as well as the future perspectives in this field. Beginning with the fundamentals of ferroelectric materials, Ferroelectric Materials for Energy Applications offers in-depth chapter coverage of: piezoelectric energy generation; ferroelectric photovoltaics; organic-inorganic hybrid perovskites for solar energy conversion; ferroelectric ceramics and thin films in electric energy storage; ferroelectric polymer composites in electric energy storage; pyroelectric energy harvesting; ferroelectrics in electrocaloric cooling; ferroelectric in photocatalysis; and first-principles calculations on ferroelectrics for energy applications. -Covers a highly application-oriented subject with great potential for energy conversion and storage applications. -Focused toward a large, interdisciplinary group consisting of material scientists, solid state physicists, engineering scientists, and industrial researchers -Edited by the "father of integrated ferroelectrics" Ferroelectric Materials for Energy Applications is an excellent book for researchers working on ferroelectric materials and energy materials, as well as engineers looking to broaden their view of the field.
Ferroelectric materials have been and still are widely used in many applications, that have moved from sonar towards breakthrough technologies such as memories or optical devices. This book is a part of a four volume collection (covering material aspects, physical effects, characterization and modeling, and applications) and focuses on the application of ferroelectric devices to innovative systems. In particular, the use of these materials as varying capacitors, gyroscope, acoustics sensors and actuators, microgenerators and memory devices will be exposed, providing an up-to-date review of recent scientific findings and recent advances in the field of ferroelectric devices.
Ferroelectric materials are known and valued for their multifunctionality arising from the possibility to perturb the remnant ferroelectric polarization by electric field, temperature and/or mechanical stimuli. While inorganic ferroelectrics dominate the current market, their organic counterparts may provide highly desired properties like eco-friendliness, easy processability and flexibility, concomitantly opening unique opportunities to combine multiple functionalities into a single compound that facilitates unprecedented device concepts and designs. Supramolecular organic ferroelectrics of columnar discotic type, that are the topic of this thesis, offer additional advantages related to their strong hierarchical self-assembly and easy tunability by molecular structure modifications, allowing optimization of ferroelectric characteristics and their hybridization with, e.g., semiconductivity. This not only leads to textbook ferroelectric materials that can be used as model systems to understand the general behaviour of ferroics, but also gives rise to previously unobserved effects stemming from the interplay of different functionalities. The core-shell structure of the molecules under the scope enables multiple pathways forrational design by molecular structure modification. This was firstly pursued via peripheral tail engineering on an archetypal self-assembling ferroelectric trialkylbenzene-1,3,5-tricarboxamide (BTA). We found that by shortening the alkyl chain length all the ferroelectric properties can be continuously tuned. In particular, changing the tail from C18H37 to C6H13causes an increase in depolarization activation energy (~0.8 eV to ~1.55 eV), coercive field(~25 V/?m to ~50 V/?m) and remnant polarization (~20 mC/m2 to ~60 mC/m2). The combination of the mentioned characteristics resulted in a record polarization retention time of close to 3 months at room temperature for capacitor devices of the material having the shortest alkyl chain – BTA-C6, which at the time of writing was one of the best results for liquid-crystalline ferroelectrics. Taking one step further, we experimentally demonstrated how introduction of branched-tailsubstituents results in materials with a wide operating temperature range and a data retention time of more than 10 years in thin-film solution-processed capacitor devices already atelevated temperatures with no measurable depolarization at room temperature. The observed differences between linear- and branched-tail compounds were analysed using density functional theory (DFT) and molecular dynamics (MD) simulations. We concluded that morphological factors like improved packing quality and reduced disorder, rather than electrostatic interactions or intra/inter-columnar steric hindrance, underlay the superior properties of the branched-tailed BTAs. Synergistic effects upon blending of compounds with branched and linear sidechains were shown to further improve the materials’ characteristics. Exploiting the excellent ferroelectric performance and the well-defined nanostructure of BTAs, we experimentally determined the Preisach (hysteron) distribution of BTA and confronted it to the one obtained for the semi-crystalline P(VDF:TrFE). This allowed to elucidate how the broadening of the Preisach distribution relates to the materials’ morphology. We further connected the experimental Preisach distribution to the corresponding microscopic switching kinetics. We argue that the combination of the two underlays the macroscopic dispersive switching kinetics as commonly observed for practical ferroelectrics. These insights lead to guidelines for further advancement of ferroelectric materials both for conventional and multi-bit data storage applications. Although having strong differences in the Preisach distribution, BTA and P(VDF:TrFE) both demonstrate negative piezoelectricity – a rare anomalous phenomenon which is characteristic to two-phased materials and has never been observed in small-molecular ferroelectrics. We measured a pronounced negative piezoelectric effect in a whole family of BTAs and revealed its tunability by mesogenic tail substitution and structural disorder. While the large- and small-signal strain in highly ordered thin-film BTA capacitor devices are dominated by intrinsic contributions and originates from piezostriction, rising disorder introduces additional extrinsic factors that boost the large-signal d33 up to ?20 pm/V in short-tailed molecules. Interestingly, homologues with longer mesogenic tails show a large-signal electromechanical response that is dominated by the quadratic Maxwell strain with significant mechanical softening upon polarization switching, whereas the small-signal strain remains piezostrictive. Molecular dynamics and DFT calculations both predict a positive d33 for defect-free BTA stacks. Hence, the measured negative macroscopic d33 is attributed to the presence of structural defects that enable the dimensional effect to dominate the piezoelectric response of BTA thin films. The true multifunctionality of supramolecular discotics manifests when large semiconducting cores surrounded by field-switchable strongly polar moieties are introduced in the structure. We showed how the combination of switchable dipolar side groups and the semiconducting core of the newly synthetized C3-symmetric benzotristhiophene molecule (BTTTA) leads to an ordered columnar material showing continuous tunability from injection- to bulk-limited conductivity modulation. Both these resistive switching mechanisms may lead to the next-generation high-density non-volatile rewritable memory devices with high on/off ratios and non-destructive data readout – the element that has been desperately sought after to enablefully organic flexible electronics. Utbredd elektronisering och det högst aktuella fenomenet sakernas internet (Internet of Things) ställer höga krav på nästa generations elektroniska system. Produkterna ska vara lätta att framställa med miljövänliga metoder, låg kostnadsproduktion och skalbarhet (t. ex. tryckt elektronik), återvinningsbarhet eller biologisk nedbrytbarhet (gällande engångselektronik), mekanisk flexibilitet (formbara bärbara system), kemisk stabilitet, till och med biokompatibilitet (t. ex. implanterbara system) – dessa är bara några utmaningar som den kommande tekniken behöver övervinna. Organiska material kan åstadkomma alla dessa önskade egenskaper, samtidigt som man skapar unika möjligheter att kombinera flera funktionaliteter till en enda sammansättning som underlättar nydanande komponenter och design. Ferroelektriska material kännetecknas av pyroelektriska, piezoelektriska och dielektriska egenskaper. Denna mångsidighet möjliggör icke-flyktiga minnesenheter, temperatur- och taktila sensorer, olika transduktorer och manöverdon, som alla baseras på förändringar av den ferroelektriska restpolarisationen genom fält-, temperatur- och / eller mekaniska stimuleringar. Diskformade supramolekylära organiska ferroelektriska ämnen ger ytterligare fördelar tack vare deras modifierbara molekylstrukturer och starka hierarkiska självorganisation som staplar diskarna i kolumner. På detta sätt kan lättbearbetningsbara organiska ferroelektriska material med hög restpolarisering och extrem datalagring konstrueras molekylärt. På grund av deras väldefinierade nanostrukturer kan sådana material användas som modellsystem för att förstå det allmänna beteendet hos polykristallina ferroelektriska material. De uppvisar också ensällsynt negativ piezoelektricitet som är atypisk för små molekylära material och härrör från deras komplexa nanostruktur. Den verkliga multifunktionaliteten hos diskformade supramolekylära ämnen framträder när stora halvledande kärnor omgivna av starkt polära delar, som är växlingsbara via ett elektriskt fält, introduceras i strukturen. Oöverträffad resistiv omkoppling, inducerad av den asymmetriska laddningstransporten beroende på polarisationsriktningen med rekordhög datalagringstid, upptäcktes efter optimering av molekylstrukturen. Även en konceptuellt enklare resistiv omkopplingsmekanism bunden till en modulation av laddningsinjektionsbarriären genom gränssnittsdipolerna observerades. Båda dessa fenomen kan bidra till nästa generations icke-flyktiga överskrivningsbara minnesenheter med högdensitet, stora på av-förhållanden, och icke-destruktiv dataavläsning – vilket är kritiskt för att möjliggöra helt organisk flexibel elektronik.
The continued digitalization of our society means that more and more things are getting connected electronically. Since currently used inorganic electronics are not well suited for these new applications because of costs and environmental issues, organic electronics can play an important role here. These essentially plastic materials are cheap to produce and relatively easy to recycle. Unfortunately, their poor performance has so far hindered widespread application beyond displays. One key component of any electronic device is the memory. For organic electronics several technologies are being investigated that could serve as memories. One of these are the ferroelectrics, materials that have a spontaneous electrical polarization that can be reversed with an electric field. This bistable polarization which shows hysteresis makes these materials excellent candidates for use as memories. This thesis focuses on a specific type of organic ferroelectric, the supramolecular discotics. These materials consist of disk?like molecules that form columns in which all dipolar groups are aligned, giving a macroscopic ferroelectric polarization. Of particular interest are the benzenetricarboxamides (BTA), which are used as a model system for the whole class of discotic ferroelectrics. BTA uses a core?shell architecture which allows for easy modification of the molecular structure and thereby the ferroelectric properties. To gain a deeper understanding of the switching processes in this organic ferroelectric BTA, both microscopic and analytical modeling are used. This is supported by experimental data obtained through electrical characterization. The microscopic model reduces the material to a collection of dipoles and uses electrostatics to calculate the probability that these dipoles flip. These flipping rates are the input for a kinetic Monte Carlo simulation (kMC), which simulates the behavior of the dipoles over time. With this model we simulated three different switching processes on experimental time and length scales: hysteresis loops, spontaneous depolarization, and switching transients. The results of these simulations showed a good agreement with experiments and we can rationalize the obtained parameter dependencies in the framework of thermally activated nucleation limited switching (TA?NLS). The microscopic character of the model allows for a unique insight into the nucleation process of the polarization switching. We found that nucleation happens at different locations for field driven polarization switching as compared to spontaneous polarization switching. Field?driven nucleation happens at the contacts, whereas spontaneous depolarization starts at defects. This means that retention times in disordered ferroelectrics could be improved by reducing the disorder, without affecting the coercive field. Detailed analysis of the nucleation process also revealed a critical nucleation volume that decreases with applied field, which explains the Merz?like field?dependence of the switching time observed in experiments. In parallel to these microscopic simulations we developed an analytical framework based on the theory of TA?NLS. This framework is mainly focused on describing the switching transients of disordered ferroelectrics. It can be combined with concepts of the Preisach model, which considers a non?ideal ferroelectric as a collection of ideal hysterons. We were able to relate these hysterons and the distribution in their up? and down?switching fields to the microscopic structure of the material and use the combined models to explain experimentally observed dispersive switching kinetics. Whereas ferroelectrics on their own could potentially serve as memories, the readout of ferroelectric memories becomes easier if they are combined with semiconductors. We have introduced several molecular materials following the same design principle of a core?shell structure, which uniquely combine ferroelectricity and semiconductivity in one material. The experimental IV?curves of these materials could be described using an asymmetric Marcus hopping model and show their potential as memories. The combination of modeling and experimental work in this thesis thereby provides an increased understanding of organic ferroelectrics, which is crucial for their application as memories.
Combining both fundamental principles and real-life applications in a single volume, this book discusses the latest research results in ferroelectrics, including many new ferroelectric materials for the latest technologies, such as capacitors, transducers and memories. The first two chapters introduce dielectrics and microscopic materials properties, while the following chapter discusses pyroelectricity and piezoelectricity. The larger part of the text is devoted to ferroelectricity and ferroelectric ceramics, with not only their fundamentals but also applications discussed. The book concludes with a look at the future for laser printed materials and applications. With over 600 references to recent publications on piezoelectric and ferroelectric materials, this is an invaluable reference for physicists, materials scientists and engineers.
This book provides comprehensive, state-of-the art coverage of photorefractive organic compounds, a class of material with the ability to change their index of refraction upon illumination. The change is both dynamic and reversible. Dynamic because no external processing is required for the index modulation to be revealed, and reversible because the index change can be modified or suppressed by altering the illumination pattern. These properties make photorefractive materials very attractive candidates for many applications such as image restoration, correlation, beam conjugation, non-destructive testing, data storage, imaging through scattering media, holographic imaging and display. The field of photorefractive organic material is also closely related to organic photovoltaic and light emitting diode (OLED), which makes new discoveries in one field applicable to others.
Organic electronics represent a realistic alternative to conventional silicon-based technologies through the design, synthesis and implementation of functional organic materials into light and flexible devices. Organic materials, such as small molecules or organic polymers, are advantageous for their low-cost, flexibility and easy processing. Thanks to the economical and timesaving advantages, organic electronics have emerged as an innovative field with application in energy, environment, health, information and communication technologies.Organic electronics originates from the discovery of polymers with semiconducting functionalities. However, one should not neglect another class of outstanding polymers, the ferroelectric polymers. The electroactive nature of ferroelectric polymers, which are also pyroelectric and piezoelectric, combined with the intrinsic advantages of polymers have designated them as constituent elements of a widespread range of organic electronic devices. The most well-known family of ferroelectric polymers is that of poly(vinylidene fluoride), P(VDF), and its copolymers with trifluoroethylene, P(VDF-co-TrFE). Energy harvesting, data storage and sensing, main applications of organic electronics, can potentially all be realised using these exceptional functional materials.Since ferroelectricity is a structure-dependent property an insight into the interrelations between structure and final ferroelectric properties is indispensable in order to improve existing applications of ferroelectric polymers in organic electronics and to promote the introduction of P(VDF-co-TrFE) in new application fields. P(VDF-co-TrFE) as semi-crystalline polymer possess crystalline properties which are sensitive to thermal treatment. Since only the crystalline regions contribute to ferroelectric switching and not the amorphous ones, the degree of crystallinity is a key factor to modulate the ferroelectric properties. Moreover, crystallites orientation as well as the presence of defects within the crystallites are crucial parameters playing an important role in defining the final performance of the devices in which P(VDF-co-TrFE) is incorporated.Herein stands the aim of this thesis: reach an exhaustive understanding of processing-structure-function relationships that will serve as tool to modulate ferroelectric devices performances.Going one step further, the potential applications of P(VDF-co-TrFE) in organic electronics are explored by investigating it in: (1) medical piezoelectric catheter sensors for measuring cardiac function and eventually for detecting cardiac disease and (2) electronic devices in which P(VDF-co-TrFE) is blended with the semiconducting polymer poly(3-hexylthiophene), P3HT. The latter has already been applied in non-volatile ferroelectric memory diodes and the potential use in organic photovoltaics is explored.
Combining both fundamental principles and real-life applications in a single volume, this book discusses the latest research results in ferroelectrics, including many new ferroelectric materials for the latest technologies, such as capacitors, transducers and memories. The first two chapters introduce dielectrics and microscopic materials properties, while the following chapter discusses pyroelectricity and piezoelectricity. The larger part of the text is devoted to ferroelectricity and ferroelectric ceramics, with not only their fundamentals but also applications discussed. The book concludes with a look at the future for laser printed materials and applications. With over 600 references to recent publications on piezoelectric and ferroelectric materials, this is an invaluable reference for physicists, materials scientists and engineers.
