The increasing use of disposable sensor devices has raised concerns regarding environmental contamination and resource sustainability. However, design principles for disposable sensor systems under explicit material constraints have not been sufficiently explored. In this work, we propose a material-oriented design framework for disposable sensor systems based on hazard potential and elemental abundance. Guided by this framework, we develop an organic complementary transistor with carbon-based electrodes and a magnesium–air battery designed to avoid selected regulated hazardous substances and elements with low crustal abundance under the proposed criteria. As a proof of concept, we implement a disposable moisture-responsive sensor node integrating the developed transistor and battery. The implemented node generated a supply voltage of 14.8–15.6 V after moisture activation and transmitted a 3-bit ID at 6.7 bit/s using a 140-Hz carrier. We further fabricate and experimentally verify a single-chip integrated sensor circuit, confirming the essential circuit functions required for the proposed sensor node. These results demonstrate a material-constrained design methodology for disposable event-detection sensor nodes, in which the power source, sensing activation mechanism, and organic circuit are co-designed to reduce material-related concerns.

The control of heat transport in organic materials has attracted increasing attention for developing thermal transistors and other heat-regulating devices. Here, we demonstrate continuous and reversible modulation of the thermal conductivity (kappa perpendicular to\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\kappa }_{\perp }$$\end{document}) of polymer poly[2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) films along the lamellar-stacking (out-of-plane) direction via electrochemical doping. kappa perpendicular to\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\kappa }_{\perp }$$\end{document} values were quantitatively evaluated under gating conditions using a gold-based time-domain thermoreflectance system. Upon electrochemical doping, kappa perpendicular to\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\kappa }_{\perp }$$\end{document} increased by 28%, from 0.198 to 0.253 W m-1 K-1, and the modulation of the thermal conductivity by the shift of gate voltage is achieved. Atomistic simulations revealed how molecular intercalation and the associated changes in local structural conformation affect spectral thermal transport in the host PBTTT matrix, providing insight into the mechanism behind the increased kappa perpendicular to\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\kappa }_{\perp }$$\end{document}. These results confirm that electrochemical doping enables reversible and controllable tuning of thermal conductivity, a key requirement for thermal management applications, paving the way for future advancements in thermally tunable organic materials.

Doping is a cornerstone of semiconductor engineering, yet conventional methods lack precise and uniform control over electronic properties. Here, we present a highly controllable voltage-programmed electrochemical doping strategy utilizing pulsed gate voltage sequences to orchestrate anion/cation ingress into polymer matrices. This approach, applied to the benchmark semicrystalline p-type polymer poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) and the cyano-functionalized bithiophene imide dimer (CNI2)-based n-type polymer, overcomes the limitations of chemical doping by delivering exceptional scalability and tunability, achieving conductivities of up to 685 and 21 S cm- 1, respectively. These gains arise from optimized electronic properties and enhanced polymer crystallinity enabled by precise voltage-driven ion intercalation. Notably, this enables a Hall mobility of 2.6 cm2 V- 1 s- 1 at 300 K and signatures of mesoscopic phase-coherent transport, as evidenced by the observation of Hall effect signals and positive magnetoresistance associated with weak localization. This study establishes a generalizable framework for engineering charge transport in conjugated polymers for advanced electronic and spintronic applications.

Molecular doping has enabled control of electronic properties in semiconducting polymers for studies of charge transport and device applications. However, conventional dopant anions are mostly organic monovalent species whose roles are largely limited to stable charge compensation. Here, we introduce polyoxometalates as multivalent oxide-cluster dopant ions into semicrystalline polymer semiconductors. In particular, films doped with size-compatible divalent [W _6 O _19 ] $ ^{2-}$ retain lamellar order, exhibit conductivity above 200 S cm $ ^{-1}$ , and show a Hall response, indicating partially coherent carrier transport. Compared with inert-anion-doped films, [W _6 O _19 ] $ ^{2-}$ -doped films show enhanced anodic response in the oxygen-evolution region, demonstrating functional multivalent-ion doping for electronic and electrocatalytic polymer semiconductor films.

Exciton dissociation into free electron-hole carriers is a central issue in optoelectronic devices. Despite recent progress in free-carrier generation due to an admixture of organic compounds, strategies to prolong the lifetime of photo-induced carriers are limited. Herein, we present a proof-of-concept of efficient exciton dissociation via heterogeneous device engineering; an insulating polymer layer adjacent to organic semiconductors (OSCs) in conjunction with an application of electrical voltage can capture photogenerated electrons selectively, and the resulting semipermanent built-in electric field gives rise to extraordinarily persistent photo-induced carriers, which lasts for more than half a year in single-crystalline OSCs.

A highly periodic electrostatic potential and coherent band transport can emerge in organic molecular crystals, despite weak van der Waals interactions. Although charge carrier mobility in single-crystalline organic semiconductors (OSCs) reaches 10 square centimeters per volt per second (cm2 V-1 s-1), it is predominantly limited by molecular vibrations excited at room temperature. The extent to which mobility in single-crystalline OSCs can be increased remains a central question. Here, we demonstrate charge transport in a clean two-dimensional hole gas (2DHG) in uniaxially strained, single-crystalline OSCs at cryogenic temperatures, with minimized lattice vibrations. Hall effect measurements reveal a mobility of 117 cm2 V-1 s-1 at 2 kelvin under 2.8% compressional strain, with an extraordinarily large piezoresistive effect and low sheet resistivity of 550 ohms, one-fifth of the lowest resistivity in unstrained samples. These clean systems offer opportunities to explore intrinsic strain-induced charge transport physics, where condensed matter phenomena, characterized by weakly bonded molecular orbitals, combine electronic correlation and lattice degrees of freedom.

Solution processing of polymeric semiconductors provides a facile way to fabricate functional diodes. However, energy barriers at metal-semiconductor interfaces often limit their performance. Here, we report rectifying polymer diodes with markedly modified energy-level alignments. The gold electrode surface was treated with a dimeric metal complex, which resulted in a shallow work function of 3.7 eV by forming a monolayer-thick ionized donor layer. When a polymeric semiconductor was coated on the treated electrode, most of the ionized donors remained at the metal-semiconductor interface. The confined ionized donors with the ideal thickness enabled fabrication of a polymer diode with a forward current density of over 100 A cm-2. Furthermore, a power conversion efficiency of 7.9% was observed for rectification at a microwave frequency of 920 MHz, which is orders of magnitude higher than that reported for organic diodes. Our findings will pave a way to solution-processed high-frequency and high-power devices.

Doped interlayers were employed to improve charge injection from copper electrodes into high-mobility organic single-crystal semiconductors, addressing both economic and material sustainability challenges in organic electronics.

Organic semiconductor (OSC) single crystals feature flexibility, solution processability, and high-mobility coherent carrier transport, which are advantageous for printed flexible electronic applications. A mechanical strain sensor is a target device whose high sensitivity and wide measurement range have been demonstrated when OSC single crystals were employed as the active channel. However, there have been limited reports on scalable fabrication of devices and reliable measurements, which limits the use of strain sensors in a wide range of applications. In this study, we present a comprehensive approach to address these issues through advanced device processing, design, and measurements. Our resistive strain sensors showed a small drift owing to the stable and effective p-type chemical doping of the OSC single crystals. A Wheatstone bridge circuit and compact lock-in amplifier were designed to accurately measure resistance changes at low noise levels. The experimental results demonstrated a substantial reduction in noise and achieved high-precision measurements with precision of ± 1.8 ppm. These results demonstrate the scalable fabrication of organic semiconductor strain sensors with high precision and reliability, which opens up the possibility of employing them in various industrial sectors.

Strong electron correlation is the essential mediator that creates various exotic phases in two-dimensional electronic systems which has been continuously intriguing in modern condensed-matter physics. Such electronic states as Mott insulators, charge orders, and high-temperature superconductivity would be simply Fermi-degenerated metals unless the strong correlation plays essential roles. However, how it emerges, particularly to overcome screening effects upon doping band insulators, has not been experimentally studied. In this study, we report evolution of a strongly correlated electron system from a band-insulating organic semiconductor. Carriers are continuously doped via electric double layers up to a density of 1014 cm-2. Notably, significant deviations from a simple metallic system are observed even at far from half-filled band, possibly due to charge-order instability. The findings reveal that off-site Coulomb energy can compete with Thomas-Fermi screening. This competition enables the emergence of strongly correlated exotic phases, even in systems distant from Mott insulators.

Transistors fabricated from thin‐film single crystals of organic semiconductors (OSCs) have exhibited high mobility exceeding 10 cm 2 V −1 s −1 and show compatibility with low‐cost solution processing. However, their carrier mobility is limited by the molecular vibrations in their soft lattices. This study establishes a practical method for applying compressive strain to single‐crystal OSCs to enhance mobility and transistor performance. In this method, a polymer film substrate is bent to mechanically stretch its surface. Organic single‐crystal transistors are then laminated onto the stretched surface of substrate. Releazing the stretch by recovering the flat surface of the substrate allowed the transistors to be compressed by up to 3%. This resulted in a 52% increase in mobility, reaching 26.4 cm 2 V −1 s −1 . X‐ray diffraction measurements confirmed lattice strain in the OSC single crystals. Moreover, carrier mobility and cutoff frequency increased in MHz‐operating short‐channel transistors, demonstrating applicability for high‐frequency devices. The mobility increase is maintained even three years after introducing the 1% compressive strain, possibly owing to the flexible, molecularly thin characteristics of OSC single crystals. The proposed strain management methods may provide new avenues to enhance the performance of high‐mobility and high‐frequency electronic devices based on OSC thin‐film single crystals.

The crystal structure of organic semiconductors is an important factor that dominates various electronic properties, including charge transport properties. However, compared with the crystal structures of inorganic semiconductors, those of organic semiconductors are difficult to determine by powder x-ray diffraction (PXRD) analysis. Our proposed machine-learning (neural-network) technique can determine the diffraction peaks buried in noise and make deconvolution of the overlapped peaks of organic semiconductors, resulting in crystal-structure determination by the Rietveld analysis. As a demonstration, we apply the method to a few high-mobility organic semiconductors and confirm that the method is potentially useful for analyzing the crystal structure of organic semiconductors. The present method is also expected to be applicable to the determination of complex crystal structures in addition to organic semiconductors.

Schematic diagram of the preparation of a hydrophobic CNC/CNT interface.

Owing to the growing global increase in electronic and electrical waste (e-waste), significant challenges arise regarding the proper disposal of electronic devices. One potential solution that has gained attention is the development of disposable electronics, in which all components are designed to be for safe and environmentally friendly disposal. In this study, all-carbon-based complementary integrated circuits composed of printed single-crystalline thin films of p- and n-type organic semiconductors, graphite-based carbon electrodes/wiring, and polymeric dielectrics/substrates are demonstrated. Elemental analysis reveals that the total amount of metallic element contaminants weighed <50 parts per million (ppm). The demonstrated analog/digital integrated circuits with 64 p- and n-type organic thin-film transistors exhibit stable operation under ambient environmental conditions. These all-carbon-based complementary integrated circuits possess excellent element traceability, thus mitigating the potential environmental impacts throughout the device's life cycle. Consequently, this advancement represents a significant step toward addressing the global environmental challenges associated with e-waste.

Control of electrical doping is indispensable in any semiconductor device, and both efficient hole and electron doping are required for many devices. In organic semiconductors, however, electron doping has been essentially more problematic compared to hole doping because in general organic semiconductors have low electron affinities and require dopants with low ionization potentials that are often air-sensitive. Here, we adapt an efficient molecular doping method, so-called ion-exchange doping, to dope electrons in a polymeric semiconductor. We initially reduce the polymeric semiconductor using one electron transfer from molecular dopants, and then the ionized dopants in the resulting air-unstable films are replaced with secondary ions via cation exchange. Improved ambient stability and crystallinity of the doped polymeric semiconductors are achieved when a specific bulky molecular cation was chosen as the secondary ion, compared to conventional methods. The presented strategy can overcome the trade-off relationship between reducing capability and ambient stability in molecular dopants, and a wider selection of dopant ions will help to realize ambient-stable electron conductors. It is difficult to control electron doping in organic semiconductors because they often require dopants that are air-sensitive. Here, an ion-exchange doping method is introduced with improved ambient stability and crystallinity of the doped polymeric semiconductors compared to conventional methods.

The era of Internet of Things (IoT) is arriving as electronic devices have become ubiquitous. Engineers have incorporated various harmful substances and scarce elements into electronic devices for improving their performance. Disposable uses cases, such as moisture sensors or thermometers, are also increasing. As a result, a large amount of electronic devices causes electronic and electrical wastes (e-wastes), and this has become a global environmental problem. When the electronic devices are discarded without recycling, the harmful substances in them pollute the soil and water (Fig. 17.4.1). In addition, the use of scarce elements deplete resources, causing economic conflicts. For a sustainable society, disposable electronic devices should use only materials that do not harm the environment or deplete resources.

Notorious Zn dendrites and severe parasitic side reactions severely disrupt the anode-electrolyte interface during Zn plating/stripping, resulting in uncontrollable Zn deposition and limiting the application of aqueous zinc-ion batteries (AZIBs). Although the construction of an artificial interface is a highly desirable strategy, it is often limited by slow Zn2+ transport kinetics. To address these issues, we present a bifunctional polymer coating (PEPM) constructed from highly conductive PEDOT:PSS and monolayer MoS2, where the introduced PEDOT plays an important role in driving the fast Zn ion transfer kinetics as a zincophilic site and 2D MoS2 acts as a buffer layer to induce uniform Zn nucleation. With this corrosion inhibition and nucleation-oriented coating, the mobility of Zn2+ flux and the uniformity of Zn deposition were significantly improved, resulting in a stable plating/stripping performance at an ultra-low overpotential (<50 mV) of 2000 h and a high average coulombic efficiency (>99.4%) of 1000 cycles without significant dendrite formation. The proposed strategy provides a cost-efficient remedy and opens a new avenue for the development of dendrite-free zinc anodes.

Thin-film devices that transduce the chemical activity of ions into electronic signals are essential components in various applications, including healthcare diagnostics and environmental monitoring. Combinations of organic semiconductors (OSCs) and ion- selective materials have been explored for developing solution-processable ion sensors. However, the necessity of reference electrodes (REs) and operational stability in ion- permeable OSCs have posed questions regarding whether reliable measurements with thin-film components are attainable with OSCs. Herein, we report electric double-layer transistors (EDLTs) with OSCs in single-crystal forms for ion sensing. Our EDLTs demonstrated high operational stability, with a one-to-one relationship between the source electrode potential and device resistance, and served as quasi-REs (qRE). When our EDLT is served as qRE, its drift was as small as 0.5 mV/h and comparable to that of commonly employed REs. In our system, the semiconductor-electrolyte interface is self-passivated by the alkyl chains of OSCs in single-crystal structures, with the two-dimensional transport layer appearing unaltered upon gating. EDLT arrays with ion-selective and nonselective liquid junctions enable ion concentration sensing without a conventional RE. These findings provide opportunities to develop thin-film devices based on OSCs for easy integration and reliable measurements.

In this study, an artificial interfacial layer (PANI-C) for Zn anode consisting of hydrophilic cellulose nanocrystals and polyaniline was designed to address the dendrite growth problem at the electrode/electrolyte interface in aqueous Zn-ion batteries. Benefiting from the synergistic effect of high electronegativity and abundant surface functional groups, PANI-C accelerates the ordered migration of Zn2+, homogenizes the cosolvent of Zn2+ and effectively improves the reversibility of the zinc plating process, with strong zincophilicity and inhibition of dendrites. In addition, the PANI-C layer has abundant carbonyl adsorption sites uniformly distributed at the molecular level, and exhibits good ionic modulation ability during the Zn2+ plating/stripping process. The Zn||Cu asymmetric cell exhibited excellent reversibility with an average Coulombic efficiency of 99.3% after 1000 cycles at 1 mA cm(-2). The assembled PANI-C@Zn//V2O5 full cell maintains 94.6% of its original capacity at 1 A g(-1) after 2500 h, with an ultralong cycling time of 1500 h instantly even at a high current density of 5 A g(-1). This strategy provides insight into the design of dendrite-free zinc anodes and highlights their applicability for practical zinc-based energy storage in the future.

AbstractPoly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is a prototypical conducting polymer. When a polar solvent is used during film fabrication, the hole-doped PEDOT oligomers form crystalline clusters in the films, exhibiting high conductivity. However, whether hole carriers exhibit band transport has not been clarified yet. Here, we employ a multilayer spin-coating method using an aqueous solution with ethylene glycol, with additional procedures of dipping the films in ethylene glycol or dropping sulfuric acid onto the films, to achieve a high DC conductivity of ∼1000 S cm−1 or higher. Using terahertz time-domain spectroscopy and far-infrared-to-ultraviolet reflection spectroscopy, we derive complex optical conductivity $$\widetilde{\sigma }$$ σ ̃ spectra, which are reproduced by the sum of the Drude response, and Lorentz-oscillator responses due to phonons. These results demonstrate the band transport, which is further confirmed by the Hall effect measurements. The hole mobility estimated from the spectral analyses is 7–11 cm2 V−1 s−1, a significantly large value. The reported evaluation methods for broadband $$\widetilde{\sigma }$$ σ ̃ spectra can help elucidate carrier transport mechanisms in various conducting films.