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We report a flexible self-standing adhesive composite made from PEDOT:PSS and nanofibrillated cellulose. The material exhibits good combined mechanical and electrical characteristics (an elastic modulus of 4.4 MPa, and an electrical conductivity of 30 S cm(-1)). The inherent self-adhesiveness of the material enables it to be laminated and delaminated repeatedly to form and reconfigure devices and circuits. This modular property opens the door for a plethora of applications where reconfigurability and ease-of-manufacturing are of prime importance. We also demonstrate a paper composite with ionic conductivity and combine the two materials to construct electrochemical devices, namely transistors, capacitors and diodes with high values of transconductance, charge storage capacity and current rectification. We have further used these devices to construct digital circuits such as NOT, NAND and NORlogic., QC 20180130

Ionic thermoelectric materials, for example, polyelectrolytes such as polystyrene sulfonate sodium (PSSNa),constitute a new class of materials which are attracting interest because of their large Seebeck coefficientand the possibility that they could be used in ionic thermoelectric SCs (ITESCs) and field effect transistors.However, pure polyelectrolyte membranes are not robust or flexible. In this paper, the preparation of ionicthermoelectric paper using a simple, scalable and cost-effective method is described. After a compositewas fabricated with nanofibrillated cellulose (NFC), the resulting NFC–PSSNa paper is flexible andmechanically robust, which is desirable if it is to be used in roll-to-roll processes. The robust NFC–PSSNa thermoelectric paper combines high ionic conductivity (9 mS cm1), high ionic Seebeckcoefficient (8.4 mV K1) and low thermal conductivity (0.75 W m1 K1) at 100% relative humidity,resulting in overall figure-of-merit of 0.025 at room temperature which is slightly better than that for thePSSNa alone. Fabricating a composite with cellulose enables flexibility and robustness and this is anadvance which will enable future scaling up the manufacturing of ITESCs, but also enables its use fornew applications for conformable thermoelectric devices and flexible electronics.

Poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) has been reported as a successful functional material in a broad variety of applications. One of the most important advantages of PEDOT:PSS is its water-solubility, which enables simple and environmental friendly manufacturing processes. Unfortunately, this also implies that pristine PEDOT:PSS films are unsuitable for applications in aqueous environments. To reach stability in polar solvents, (3-glycidyloxypropyl)trimethoxysilane (GOPS) is typically used to cross-link PEDOT:PSS. Although this strategy is widely used, its mechanism and effect on PEDOT:PSS performance have not been articulated yet. Here, we present a broad study that provides a better understanding of the effect of GOPS on the electrical and electronic properties of PEDOT:PSS. We show that the GOPS reacts with the sulfonic acid group of the excess PSS, causing a change in the PEDOT:PSS film morphology, while the oxidation level of PEDOT remains unaffected. This is at the origin of the observed conductivity changes. (c) 2017 Wiley Periodicals, Inc.

The evolution of the society is characterized by an increasing flow of information from things to the internet. Sensors have become the cornerstone of the internet-of-everything as they track various parameters in the society and send them to the cloud for analysis, forecast, or learning. With the many parameters to sense, sensors are becoming complex and difficult to manufacture. To reduce the complexity of manufacturing, one can instead create advanced functional materials that react to multiple stimuli. To this end, conducting polymer aerogels are promising materials as they combine elasticity and sensitivity to pressure and temperature. However, the challenge is to read independently pressure and temperature output signals without cross-talk. Here, a strategy to fully decouple temperature and pressure reading in a dual-parameter sensor based on thermoelectric polymer aerogels is demonstrated. It is found that aerogels made of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) can display properties of semiconductors lying at the transition between insulator and semimetal upon exposure to high boiling point polar solvents, such as dimethylsulfoxide (DMSO). Importantly, because of the temperature-independent charge transport observed for DMSO-treated PEDOT-based aerogel, a decoupled pressure and temperature sensing can be achieved without cross-talk in the dual-parameter sensor devices., Funding Agencies|European Research Council (ERC) [307596]

Organic polymer thermoelectrics (TE) as well as transition metal (TM) silicides are two thermoelectric class of materials of interest because they are composed of atomic elements of high abundatice; which is a prerequisite for mass implementation of thermoelectric (TE) solutions for solar and waste heat recovery. But both materials have drawbacks when it comes to finding low-cost manufacturing. The metal silicide needs high temperature (amp;gt;1000 degrees C) for creating TE legs in a device from solid powder, but it is easy to achieve long TE legs in this case. On the contrary, organic TEs are synthesized at low temperature from solution. However, it is difficult to form long legs or thick films because of their low solubility. In this work, we propose a novel method for the room temperature synthesis of TE composite containing the microparticles of chromium disilicide; CrSi2 (inorganic filler) in an organic matrix of nanofibrillated cellulose-poly(3,4-ethyelenedioxythiophene)-polystyrene sulfonate (NFC-PEDOT:PSS). With this method, it is easy to create long TE legs in a room temperature process. The originality of the approach is the use of conducting polymer aerogel microparticles mixed with CrSi2 microparticles to obtain a composite solid at room temperature under pressure. We foresee that the method can be scaled up to fabricate and pattern TE modules. The composite has an electrical conductivity (sigma) of 5.4 +/- 0.5 S/cm and the Seebeck coefficient (a) of 88 +/- 9 mu V/K, power factor (alpha(2)sigma) of 4 +/- 1 mu Wm(-1) K-2 at room temperature. At a temperature difference of 32 degrees C, the output power/unit area drawn across the load, with the resistance same as the internal resistance of the device is 0.6 +/- 0.1 mu W/cm(2). (C) 2017 Elsevier B.V. All rights reserved., Funding Agencies|European Research Council [307596]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; "the Power Papers project" - Knut and Alice Wallenberg foundation; RISE - the Research Institutes of Sweden; University Grants Commission, India

The interest in thermogalvanic cells (TGCs) has grown because it is a candidate technology for harvesting electricity from natural and waste heat. However, the cost of TGCs has a major component due to the use of the platinum electrode. Here, we investigate new alternative electrode material based on conducting polymers, more especially poly(3,4-ethylenedioxythiophene)-Tosylate (PEDOT-Tos) together with the Ferro/Ferricyanide redox electrolyte. The power generated by the PEDOT-Tos based TGCs increases with the conducting polymer thickness/multilayer and reaches values similar to the flat platinum electrode based TGCs. The physics and chemistry behind this exciting result as well as the identification of the limiting phenomena are investigated by various electrochemical techniques. Furthermore, a preliminary study is provided for the stability of the PEDOT-Tos based TGCs., Funding agencies: European Research Council (ERC) [307596]

An oxygen reduction reaction (ORR) mechanism in conducting polymer PEDOT is studied using the density functional theory. It is demonstrated that pure PEDOT chains possess the catalytic activity, where no platinum catalyst or external dopants are needed to sustain the electrocatalysis. This remarkable property of PEDOT is related to the formation of polaronic states, which leads to the decrease of the HOMO LUMO gap and thus to the enhancement of the reactivity of the system. It is shown that ORR on PEDOT chains can proceed via two pathways, whether via a four-electron process when the oxygen reacts with protons and is reduced directly into water in four steps (Reaction path I) or via the two-electron process leading to formation of the hydrogen peroxide as an intermediate specimen (Reaction path II). Path I is demonstrated to be energetically preferable. This conclusion also holds for ORR on two pi-pi stacked chains and ORR for the case when PEDOT is reduced during the reaction. It is also found that ORR on PEDOT effectively proceeds in the presence of H3O+ but does not occur in the absence of acidic environment., Funding Agencies|Swedish Energy Agency [38332-1]; Carl Trygges foundation [CTS: 13 527]; Troedssons Research Foundation [896/16]; J. Gust. Richert Foundation [2016-00242]; Swedish Research Council via Research Environment grant on Disposable paper fuel cells [2016-05990]; Knut and Alice Wallenberg Foundation through the project The Tail of the Sun

Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) is the most studied and explored mixed ion-electron conducting polymer system. PEDOT: PSS is commonly included as an electroactive conductor in various organic devices, e.g., supercapacitors, displays, transistors, and energy-converters. In spite of its long-term use as a material for storage and transport of charges, the fundamentals of its bulk capacitance remain poorly understood. Generally, charge storage in supercapacitors is due to formation of electrical double layers or redox reactions, and it is widely accepted that PEDOT: PSS belongs to the latter category. Herein, experimental evidence and theoretical modeling results are reported that significantly depart from this commonly accepted picture. By applying a two-phase, 2D modeling approach it is demonstrated that the major contribution to the capacitance of the two-phase PEDOT: PSS originates from electrical double layers formed along the interfaces between nanoscaled PEDOT-rich and PSS-rich interconnected grains that comprises two phases of the bulk of PEDOT: PSS. This new insight paves a way for designing materials and devices, based on mixed ion-electron conductors, with improved performance., Funding Agencies|The Swedish Energy Agency [38332-1]; Swedish Research Council [245-2010-1062]; Research Centre Security Link [VINNOVA 2009-00966]; Norrkopings fond for Forskning och Utveckling; CeNano; Knut and Alice Wallenberg Foundation; Swedish Foundation for Strategic Research (SSF); Advanced Functional Material SFO-center at Linkoping University [2009-00971]; Swedish National Infrastructure for Computing (SNIC); European Research Council (ERC) [307596, 681881]; Knut and Alice Wallenberg Foundation (Tail of the Sun); Swedish Foundation for Strategic Research [0-3D]

The conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) has shown promise as air electrode in renewable energy technologies like metal-air batteries and fuel cells. PEDOT is based on atomic elements of high abundance and is synthesized at low temperature from solution. The mechanism of oxygen reduction reaction (ORR) over chemically polymerized PEDOT: Cl still remains controversial with eventual role of transition metal impurities. However, regardless of the mechanistic route, we here demonstrate yet another key active role of PEDOT in the ORR mechanism. Our study demonstrates the decoupling of conductivity (intrinsic property) from electrocatalysis (as an extrinsic phenomenon) yielding the evidence of doping of the polymer by oxygen during ORR. Hence, the PEDOT electrode is electrochemically reduced (undoped) in the voltage range of ORR regime, but O-2 keeps it conducting; ensuring PEDOT to act as an electrode for the ORR. The interaction of oxygen with the polymer electrode is investigated with a battery of spectroscopic techniques., Funding Agencies|European Research Council (ERC) [307596]; Knut and Alice Wallenberg foundation; Wenner-Gren Foundations; Swedish Research Council; Swedish Foundation for Strategic Research [0-3D]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

Nonradiative decay of plasmons in metallic nanostructures offers unique means for light-to-heat conversion at the nanoscale. Typical thermoplasmonic systems utilize discrete particles, while metal nanohole arrays were instead considered suitable as heat sinks to reduce heating effects. By contrast, we show for the first time that under uniform broadband illumination (e.g., the sun) ultrathin plasmonic nanohole arrays can be highly competitive plasmonic heaters and provide significantly higher temperatures than analogous nanodisk arrays. Our plasmonic nanohole arrays also heat significantly more than nonstructured metal films, while simultaneously providing superior light transmission. Besides being efficient light-driven heat sources, these thin perforated gold films can simultaneously be used as electrodes. We used this feature to develop "plasmonic thermistors" for electrical monitoring of plasmon-induced temperature changes. The nanohole arrays provided temperature changes up to 7.5 K by simulated sunlight, which is very high compared to previously reported plasmonic systems under similar conditions (solar illumination and ambient conditions). Both temperatures and heating profiles quantitatively agree with combined optical and thermal simulations. Finally, we demonstrate the use of a thermoplasmonic nanohole electrode to power the first hybrid plasmonic ionic thermoelectric device, resulting in strong solar-induced heat gradients and corresponding thermoelectric voltages., Funding Agencies|Wenner-Gren Foundations; Swedish Research Council; Swedish Foundation for Strategic Research; AForsk Foundation; Knut and Alice Wallenberg Foundation; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU No 2009 00971]

Thermoelectric materials enable conversion of heat to electrical energy. The performance of electronic thermoelectric materials is typically evaluated using a figure of merit ZT = sigma alpha 2T/lambda, where sigma is the conductivity, alpha is the so-called Seebeck coefficient, and lambda is the thermal conductivity. However, it has been unclear how to best evaluate the performance of ionic thermoelectric materials, like ionic solids and electrolytes. These systems cannot be directly used in a traditional thermoelectric generator, because they are based on ions that cannot pass the interface between the thermoelectric material and external metal electrodes. Instead, energy can be harvested from the ionic thermoelectric effect by charging a supercapacitor. In this study, the authors investigate the ionic thermoelectric properties at varied relative humidity for the polyelectrolyte polystyrene sulfonate sodium and correlate these properties with the charging efficiency when used in an ionic thermoelectric supercapacitor (ITESC). In analogy with electronic thermoelectric generators, the results show that the charging efficiency of the ITESC can be quantitatively related to the figure of merit ZT(i) = sigma i alpha i2T/lambda. This means that the performance of ionic thermoelectric materials can also be compared and predicted based on the ZT, which will be highly valuable in the design of high-performance ITESCs., Funding Agencies|European Research Council (ERC-starting-grant) [307596]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

The conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is well known for its electrochromic properties in the visible region. Less focus has been devoted to the infrared (IR) wavelength range, although tunable IR properties could enable a wide range of novel applications. As an example, modern day vehicles have thermal cameras to identify pedestrians and animals in total darkness, but road and speed signs cannot be easily visualized by these imaging systems. IR electrochromism could enable a new generation of dynamic road signs that are compatible with thermal imaging, while simultaneously providing contrast also in the visible region. Here, we present the first metal-free flexible IR electrochromic devices, based on PEDOT:Tosylate as both the electrochromic material and electrodes. Lateral electrochromic devices enabled a detailed investigation of the IR electrochromism of thin PEDOT:Tosylate films, revealing large changes in their thermal signature, with effective temperature changes up to 10 [degree]C between the oxidized (1.5 V) and reduced (-1.5 V) states of the polymer. Larger scale (7 [times] 7 cm) vertical electrochromic devices demonstrate practical suitability and showed effective temperature changes of approximately 7 [degree]C, with good optical memory and fast switching (1.9 s from the oxidized state to the reduced state and 3.3 s for the reversed switching). The results are highly encouraging for using PEDOT:Tosylate for IR electrochromic applications., Funding agencies: Wenner-Gren Foundations; Swedish Research Council; Swedish Foundation for Strategic Research; AForsk Foundation; Knut and Alice Wallenberg Foundation (Tail of the sun), Vinnova as part of the Swedish national innovation program SIO Graphene; Swedish Gover

The interactions between electron donors (D) and acceptors (A) of organic semiconducting molecules are of great interest to organic electronics, e.g. electrical doping of organic semiconductors (OSCs), photo-generation of charges in organic solar cells, and light-emitting/detecting devices based on OSCs. A blend of D/A OSC is typically characterized by weak van der Waals interactions or integer charge transfer (ICT) between neighboring D/A molecules. In between these two scenarios of physical blends and ICT complexes, orbital hybridization between adjacent D/A molecules serves as a third alternative, characterized by an in situ formation of a ground state complex featuring partial charge transfer between participating donor and acceptor molecules. In this work is presented a comprehensive experimental study on partial charge-transfer complex (CPX) formed via orbital hybridization. Thiophenes and phthalocyanines are used as electron donors, while acceptor molecules of different geometries and electron affinities are employed with the aim to clarify how orbital symmetry, energy level alignment and steric hindrance affect orbital hybridization and subsequent tuning of the optical band-gap into the near infrared (NIR) region., Funding Agencies|Knut and Alice Wallenberg Foundation, project "Tail of the Sun; Swedish Research Council [2013-4022]; Goran Gustafsson Foundation for Research in Natural Sciences and Medicine; Advanced Functional Materials Center at Linkoping University; Swedish Research Council (LiLi-NFM)

Owing to changes in their chemistry and structure, polymers can be fabricated to demonstrate vastly different electrical conductivities over many orders of magnitude. At the high end of conductivity is the class of conducting polymers, which are ideal candidates for many applications in low-cost electronics. Here, we report the influence of the nature of the doping anion at high doping levels within the semi-metallic conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) on its electronic transport properties. Hall effect measurements on a variety of PEDOT samples show that the choice of doping anion can lead to an order of magnitude enhancement in the charge carrier mobility > 3 cm2/Vs at conductivities approaching 3000 S/cm under ambient conditions. Grazing Incidence Wide Angle X-ray Scattering, Density Functional Theory calculations, and Molecular Dynamics simulations indicate that the chosen doping anion modifies the way PEDOT chains stack together. This link between structure and specific anion doping at high doping levels has ramifications for the fabrication of conducting polymer-based devices.

Exploring the minute mechanical deformations induced by electrical bias at the interface with electrolytes allows the identification of local crystallinity and distinguishing adsorption and intercalation of ions in electroactive polymers.

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is the most studied and explored mixed ion-electron conducting polymer system. PEDOT:PSS is commonly included as an electroactive conductor in various organic devices, e.g., supercapacitors, displays, transistors, and energy-converters. In spite of its long-term use as a material for storage and transport of charges, the fundamentals of its bulk capacitance remain poorly understood. Generally, charge storage in supercapacitors is due to formation of electrical double layers or redox reactions, and it is widely accepted that PEDOT:PSS belongs to the latter category. Herein, experimental evidence and theoretical modeling results are reported that significantly depart from this commonly accepted picture. By applying a two-phase, 2D modeling approach it is demonstrated that the major contribution to the capacitance of the two-phase PEDOT:PSS originates from electrical double layers formed along the interfaces between nanoscaled PEDOT-rich and PSS-rich interconnected grains that comprises two phases of the bulk of PEDOT:PSS. This new insight paves a way for designing materials and devices, based on mixed ion-electron conductors, with improved performance.

A mixed ionic–electronic conductor based on nanofibrillated cellulose composited with poly(3,4-ethylene-dioxythio­phene):­poly(styrene-sulfonate) along with high boiling point solvents is demonstrated in bulky electrochemical devices. The high electronic and ionic conductivities of the resulting nanopaper are exploited in devices which exhibit record values for the charge storage capacitance (1F) in supercapacitors and transconductance (1S) in electrochemical transistors., QC 20160319

Ladder-type “torsion-free” conducting polymers (e.g., polybenzimidazobenzophenanthroline (BBL)) can outperform “structurally distorted” donor–acceptor polymers (e.g., P(NDI2OD-T2)), in terms of conductivity and thermoelectric power factor. The polaron delocalization length is larger in BBL than in P(NDI2OD-T2), resulting in a higher measured polaron mobility. Structure–function relationships are drawn, setting material-design guidelines for the next generation of conducting thermoelectric polymers. , Funded by:Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic ResearchSwedish Governmental Agency for Innovation Systems - VINNOVA. Grant Number: 2015-04859Advanced Functional Materials Center at Linköping University. Grant Number: 2009-00971Alexander von Humboldt Foundation

Electronically conducting polymers constitute an emerging class of materials for novel electronics, such as printed electronics and flexible electronics. Their properties have been further diversified to introduce elasticity, which has opened new possibility for "stretchable" electronics. Recent discoveries demonstrate that conducting polymers have thermoelectric properties with a low thermal conductivity, as well as tunable Seebeck coefficients - which is achieved by modulating their electrical conductivity via simple redox reactions. Using these thermoelectric properties, all-organic flexible thermoelectric devices, such as temperature sensors, heat flux sensors, and thermoelectric generators, are being developed. In this article we discuss the combination of the two emerging fields: stretchable electronics and polymer thermoelectrics. The combination of elastic and thermoelectric properties seems to be unique for conducting polymers, and difficult to achieve with inorganic thermoelectric materials. We introduce the basic concepts, and state of the art knowledge, about the thermoelectric properties of conducting polymers, and illustrate the use of elastic thermoelectric conducting polymer aerogels that could be employed as temperature and pressure sensors in an electronic-skin., Funding Agencies|European Research Council (ERC) [307596]; Swedish Foundation for Strategic Research; Knut and Alice Wallenberg Foundation; Swedish Energy Agency; Advanced Functional Materials Center at Linkoping University; Research Institute of Sweden (RISE)

The thermoelectric (TE) phenomena are intensively explored by the scientific community due to the rather inefficient way energy resources are used with a large fraction of energy wasted in the form of heat. Among various materials, mixed ion-electron conductors (MIEC) are recently being explored as potential thermoelectrics, primarily due to their low thermal conductivity. The combination of electronic and ionic charge carriers in those inorganic or organic materials leads to complex evolution of the thermovoltage (Voc) with time, temperature, and/or humidity. One of the most promising organic thermoelectric materials, poly(3,4-ethyelenedioxythiophene)-polystyrene sulfonate (PEDOT-PSS), is an MIEC. A previous study reveals that at high humidity, PEDOT-PSS undergoes an ionic Seebeck effect due to mobile protons. Yet, this phenomenon is not well understood. In this work, the time dependence of the Voc is studied and its behavior from the contribution of both charge carriers (holes and protons) is explained. The presence of a complex reorganization of the charge carriers promoting an internal electrochemical reaction within the polymer film is identified. Interestingly, it is demonstrated that the time dependence behavior of Voc is a way to distinguish between three classes of polymeric materials: electronic conductor, ionic conductor, and mixed ionic–electronic conductor, Funding agencies: European Research Council (ERC) [307596]

Temperature gradients are generated by the sun and a vast array of technologies and can induce molecular concentration gradients in solutions via thermodiffusion (Soret effect). For ions, this leads to a thermovoltage that is determined by the thermal gradient Delta T across the electrolyte, together with the ionic Seebeck coefficient alpha(i). So far, redox-free electrolytes have been poorly explored in thermoelectric applications due to a lack of strategies to harvest the energy from the Soret effect. Here, we report the conversion of heat into stored charge via a remarkably strong ionic Soret effect in a polymeric electrolyte (Seebeck coefficients as high as alpha(i) = 10 mV K-1). The ionic thermoelectric supercapacitor (ITESC) is charged under a temperature gradient. After the temperature gradient is removed, the stored electrical energy can be delivered to an external circuit. This new means to harvest energy is particularly suitable for intermittent heat sources like the sun. We show that the stored electrical energy of the ITESC is proportional to (Delta T alpha(i))(2). The resulting ITESC can convert and store several thousand times more energy compared with a traditional thermoelectric generator connected in series with a supercapacitor., Funding Agencies|European Research Council (ERC) [307596]; Swedish foundation for strategic research (SSF); Knut and Alice Wallenberg foundation (KAW); Swedish Energy Agency; Wenner-Gren Foundations; Advanced Functional Materials Centre at Linkoping University.The previous status of this article was Manuscript.

In electronics, the field-effect transistor (FET) is a crucial cornerstone and successful integration of this semiconductor device into circuit applications requires stable and ideal electrical characteristics over a wide range of temperatures and environments. Solution processing, using printing or coating techniques, has been explored to manufacture organic field-effect transistors (OFET) on flexible carriers, enabling radically novel electronics applications. Ideal electrical characteristics, in organic materials, are typically only found in single crystals. Tiresome growth and manipulation of these hamper practical production of flexible OFETs circuits. To date, neither devices nor any circuits, based on solution-processed OFETs, has exhibited an ideal set of characteristics similar or better than todays FET technology based on amorphous silicon. Here, bar-assisted meniscus shearing of dibenzo-tetrathiafulvalene to coat-process self-organized crystalline organic semiconducting domains with high reproducibility is reported. Including these coatings as the channel in OFETs, electric field and temperature-independent charge carrier mobility and no bias stress effects are observed. Furthermore, record-high gain in OFET inverters and exceptional operational stability in both air and water are measured., Funding Agencies|ERC [StG 2012-306826]; Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN); DGI (Spain) [BE-WELL CTQ2013-40480-R]; Generalitat de Catalunya [2014-SGR-17]; Advanced Functional Materials Center at Linkoping University; Onnesjo Foundation; Knut and Alice Wallenberg Foundation; Swedish Foundation for Strategic Research (SSF); Universidad Tecnica de Ambato; Secretaria de Educacion Superior, Ciencia, Tecnologia e Innovacion

The semiconductor-electrode interface impacts the function and the performance of (opto) electronic devices. For printed organic electronics the electrode surface is not atomically clean leading to weakly interacting interfaces. As a result, solution-processed organic ultrathin films on electrodes typically form islands due to dewetting. It has therefore been utterly difficult to achieve homogenous ultrathin conjugated polymer films. This has made the investigation of the correct energetics of the conjugated polymer-electrode interface impossible. Also, this has hampered the development of devices including ultrathin conjugated polymer layers. Here, LangmuirShafer-manufactured homogenous mono-and multilayers of semiconducting polymers on metal electrodes are reported and the energy level bending using photoelectron spectroscopy is tracked. The amorphous films display an abrupt energy level bending that does not extend beyond the first monolayer. These findings provide new insights of the energetics of the polymer-electrode interface and opens up for new high-performing devices based on ultrathin semiconducting polymers., Funding Agencies|EU project SUNFLOWER of FP7 cooperation programme [287594]; Swedish Research Council [2013-4022]; Goran Gustafsson Foundation for Research in Natural Sciences and Medicine; Swedish Research Council Linnaeus grant LiLi-NFM; Advanced Functional Materials Center at Linkoping University

Low cost and flexible devices such as wearable electronics, e-labels and distributed sensors will make the future "internet of things" viable. To power and communicate with such systems, high frequency rectifiers are crucial components. We present a simple method to manufacture flexible diodes, operating at GHz frequencies, based on self-adhesive composite films of silicon micro-particles (Si-mu Ps) and glycerol dispersed in nanofibrillated cellulose (NFC). NFC, Si-mu Ps and glycerol are mixed in a water suspension, forming a self-supporting nanocellulose-silicon composite film after drying. This film is cut and laminated between a flexible pre-patterned Al bottom electrode and a conductive Ni-coated carbon tape top contact. A Schottky junction is established between the Al electrode and the Si-mu Ps. The resulting flexible diodes show current levels on the order of mA for an area of 2 mm(2), a current rectification ratio up to 4 x 10(3) between 1 and 2 V bias and a cut-off frequency of 1.8 GHz. Energy harvesting experiments have been demonstrated using resistors as the load at 900 MHz and 1.8 GHz. The diode stack can be delaminated away from the Al electrode and then later on be transferred and reconfigured to another substrate. This provides us with reconfigurable GHz-operating diode circuits., Funding Agencies|Knut and Alice Wallenberg Foundation; Swedish Foundation for Strategic Research; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]

We report a multiscale modeling of electronic structure of a conducting polymer poly(3,4-ethylenedioxythiopehene) (PEDOT) based on a realistic model of its morphology. We show that when the charge carrier concentration increases, the character of the density of states (DOS) gradually evolves from the insulating to the semimetallic, exhibiting a collapse of the gap between the bipolaron and valence bands with the drastic increase of the DOS between the bands. The origin of the observed behavior is attributed to the effect of randomly located counterions giving rise to the states in the gap. These results are discussed in light of recent experiments. The method developed in this work is general and can be applied to study the electronic structure of other conducting polymers., Funding Agencies|Swedish Energy Agency; Knut and Alice Wallenberg Foundation (The Tail of the Sun); Carl Tryggers Foundation; SeRC; European Research Council (ERC) [307596]

Two new conjugated polymers are synthesized based on a novel donor-acceptor-acceptor (D-A-A) design strategy with the intention of attaining lower lowest unoccupied molecular obital levels compared to the normally used D-A strategy. By coupling two thieno-benzo-isoindigo units together via the phenyl position to give a new symmetric benzene-coupled di-thieno-benzo-isoindigo (BdiTBI) monomer as an A-A acceptor and thiophene (T) or bithiophene (2T) as a donor, two new polymers PT-BdiTBI and P2T-BdiTBI are synthesized via Stille coupling. The two polymers are tested in top gate and top contact field effect transistors, which exhibit balanced ambipolar charge transport properties with poly(methyl methacrylate) as dielectric and a high hole mobility up to 1.1 cm(2) V-1 s(-1) with poly(trifluoroethylene) as dielectric. The polymer films are investigated using atomic force microscopy, which shows fibrous features due to their high crystallinity as indicated by grazing incidence wide-angle X-ray scattering. The theoretical calculations agree well with the experimental data on the energy levels. It is demonstrated that the D-A-A strategy is very effective for designing low band gap polymers for organic electronic applications., Funding Agencies|Swedish Research Council; Swedish Energy Agency; EU projects SUNFLOWER "SUstainable Novel FLexible Organic Watts Efficiently Reliable" [FP7-ICT-2011-7, 287594]; National Natural Science Foundation of China [21504066]; Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy [DE-AC02-05CH11231]