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Abstract Metabolites are essential molecules involved in various metabolic processes, and their deficiencies and excessive concentrations can trigger significant physiological consequences. The detection of multiple metabolites within a non‐invasively collected biofluid could facilitate early prognosis and diagnosis of severe diseases. Here, a metal oxide heterojunction transistor (HJ‐TFT) sensor is developed for the label‐free, rapid detection of uric acid (UA) and 25(OH)Vitamin‐D3 (Vit‐D3) in human saliva. The HJ‐TFTs utilize a solution‐processed In2O3/ZnO channel functionalized with uricase enzyme and Vit‐D3 antibody for the selective detection of UA and Vit‐D3, respectively. The ultra‐thin tri‐channel architecture facilitates strong coupling between the electrons transported along the buried In2O3/ZnO heterointerface and the electrostatic perturbations caused by the interactions between the surface‐immobilized bioreceptors and target analytes. The biosensors can detect a wide range of concentrations of UA (from 500 nm to 1000 µM) and Vit‐D3 (from 100 pM to 120 nm) in human saliva within 60 s. Moreover, the biosensors exhibit good linearity with the physiological concentration of metabolites and limit of detections of ≈152 nm for UA and ≈7 pM for Vit‐D3 in real saliva. The specificity is demonstrated against various interfering species, including other metabolites and proteins found in saliva, further showcasing its capabilities.

Abstract Graphene geometric diodes, with applications in THz detection, energy harvesting, and high‐speed rectification, have been previously constrained by graphene quality and geometry feature size. This study presents significant advancements in graphene geometric diodes by employing the h‐BN/monolayer graphene/h‐BN heterojunction and extremely precise electron beam lithography. Two distinct designs of graphene geometric diodes with neck widths of 23 and 26 nm are fabricated, the superior of which demonstrated an asymmetry ratio of 1.97, a zero bias current responsivity of 0.6 A W−1, and a voltage responsivity of 12,000 V W−1, setting new benchmarks for such devices. Integrating this device into a rectification circuit, the experimentally validate that the rectified DC output voltage can be dynamically modulated and even inverted through adjustments to the diode's gate voltage. This behavior aligns seamlessly with graphene's intrinsic tunability of charge carriers, implying promising prospects for the device's application in advanced logic circuits, bidirectional switches, and signal modulation/demodulation techniques.

Abstract Crossbar circuits based on two terminal (2T) memristors typically require an additional unit such as a transistor for individual node selection. A memristive device with gate‐tunable synaptic functionalities will not only integrate selection functionality at the cell level but can also lead to enriched on‐demand learning schemes. Here, a three‐terminal (3T) mixed‐halide perovskite memristive device with gate‐tunable synaptic functions operating at low potentials is demonstrated. The device operation is controlled by both the drain (VD) and gate (VG) potentials, with an extended endurance of >2000 cycles and a state retention of >5000 s. Applying a voltage (Vset) of 20 V across the 50 µm channel switches its conductance from a high‐resistance state (HRS) to a low‐resistance state (LRS). A memristive switching mechanism is proposed that is supported by current injection models through a Schottky barrier and Kelvin probe force microscopy data. The simultaneous application of a VG potential is found to further modulate the channel conductance and reduce the operating Vset to 2 V, thus requiring a low electric field of 400 V cm−1, which is by a factor of 50× less compared to state‐of‐the‐art literature reports. Gate‐tunable retention, endurance, and synaptic functionalities are demonstrated, further highlighting the beneficial effect of VG on device operation.

The optimization of organic mixed ionic-electronic conductor is critical to realize high performance organic electrochemical transistors. Here, the authors demonstrate the removal of residual palladium impurities to be the key factor to achieving a figure-of-merit of [μC*] of over 2000 V−1 cm−1 s−1.

The incoming internet of things technology requires mass production of radiofrequency electronics. Here, Anthopoulos et al. report a self-forming nanogap method for manufacturing Schottky diodes, operating at 47 GHz, over arbitrary size substrates.

Abstract Solvent‐solvent and solvent‐anion pairings in battery electrolytes have been identified for the first time by nuclear magnetic resonance spectroscopy. These hitherto unknown interactions are enabled by the hydrogen bonding induced by the strong Lewis acid Li+, and exist between the electron‐deficient hydrogen (δ+H) present in the solvent molecules and either other solvent molecules or negatively‐charged anions. Complementary with the well‐established strong but short‐ranged Coulombic interactions between cation and solvent molecules, such weaker but longer‐ranged hydrogen‐bonding casts the formation of an extended liquid structure in electrolytes that is influenced by their components (solvents, additives, salts, and concentration), which in turn dictates the ion transport within bulk electrolytes and across the electrolyte‐electrode interfaces. The discovery of this new inter‐component force completes the picture of how electrolyte components interact and arrange themselves, sets the foundation to design better electrolytes on the fundamental level, and probes battery performances.

Achieved high thermoelectric figure of merit (ZT) in organic thermoelectric materials remains a challenge due to their low packing order and poor host/dopant miscibility. Here, the authors report side chain-engineered n-doped fullerene derivatives with record ZT >0.3 for organic thermoelectrics.

The short-range diffusion length of organic semiconductors severely limits exciton harvesting and charge generation in organic bulk heterojunction solar cells. Here, the authors report exciton diffusion length in the range of 20 to 47 nm for a wide range of non-fullerene acceptors molecules.

Improving electron transport and stability of n-type organic electrochemical transistors (OECTs) is required to realize a commercially-viable technology for bioelectronics applications. Here, the authors report water-stable doped n-type OECTs with enhanced transconductance and record stability.

Abstract There is a growing demand to attain organic materials with high electron mobility, μe, as current reliable reported values are significantly lower than those exhibited by their hole mobility counterparts. Here, it is shown that a well‐known nonfullerene‐acceptor commonly used in organic solar cells, that is, BTP‐4F (aka Y6), enables solution‐processed organic thin‐film transistors (OTFT) with a μe as high as 2.4 cm2 V−1 s−1. This value is comparable to those of state‐of‐the‐art n‐type OTFTs, opening up a plethora of new possibilities for this class of materials in the field of organic electronics. Such efficient charge transport is linked to a readily achievable highly ordered crystalline phase, whose peculiar structural properties are thoroughly discussed. This work proves that structurally ordered nonfullerene acceptors can exhibit intrinsically high mobility and introduces a new approach in the quest of high μe organic materials, as well as new guidelines for future materials design.

Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere.

Realizing phototransistors based on hybrid perovskite heterostructures with tuneable photodetection remains a challenge. Here, the authors integrate metal-halide perovskites into organic semiconductors to design hybrid heterojunction phototransistors with state-of-the-art performance.

In this paper, low earth orbit radiation (LEO), temperature, and magnetic field conditions are mimicked to investigate the suitability of flexible InGaZnO transistors for lightweight space wearables. More specifically, the impacts of high energetic electron irradiation with fluences up to 1012 e-/cm2, low operating temperatures down to 78 K and magnetic fields up to 11 mT are investigated. This simulates 278 h in LEO. The threshold voltage and mobility of transistors that were exposed to e- irradiation are found to shift by +(0.09 ± 0.05) V and -(0.6 ± 0.5) cm2V-1s-1. Subsequent low temperature exposure resulted in additional shifts of +0.38 V and -5.95 cm2V-1s-1 for the same parameters. These values are larger than the ones obtained from non-irradiated reference samples. Conversely, the performance of the devices was observed not to be significantly affected by the magnetic fields. Finally, a Cascode amplifier presenting a voltage gain of 10.3 dB and a cutoff frequency of 1.2 kHz is demonstrated after the sample had been irradiated, cooled down, and exposed to the magnetic fields. If these notions are considered during the systems design, these devices can be used to unobtrusively integrate sensor systems into space suits.

Abstract The field-effect transistor kickstarted the digital revolution that propelled our society into the information age. One member of the now large family of field-effect devices is the thin-film transistor (TFT), best known for its enabling role in modern flat-panel displays. TFTs can be used in all sorts of innovative applications because of the broad variety of materials they can be made from, which give them diverse electrical and mechanical characteristics. To successfully utilize TFT technologies in a variety of rapidly emerging applications, such as flexible, stretchable and transparent large-area microelectronics, there are a number of metrics that matter.

Abstract Metal halide perovskites (MHPs) have emerged as a frontrunner semiconductor technology for application in third generation photovoltaics while simultaneously making significant strides in other areas of optoelectronics. Photodetectors are one of the latest additions in an expanding list of applications of this fascinating family of materials. The extensive range of possible inorganic and hybrid perovskites coupled with their processing versatility and ability to convert external stimuli into easily measurable optical/electrical signals makes them an auspicious sensing element even for the high‐energy domain of the electromagnetic spectrum. Key to this is the ability of MHPs to accommodate heavy elements while being able to form large, high‐quality crystals and polycrystalline layers, making them one of the most promising emerging X‐ray and γ‐ray detector technologies. Here, the fundamental principles of high‐energy radiation detection are reviewed with emphasis on recent progress in the emerging and fascinating field of metal halide perovskite‐based X‐ray and γ‐ray detectors. The review starts with a discussion of the basic principles of high‐energy radiation detection with focus on key performance metrics followed by a comprehensive summary of the recent progress in the field of perovskite‐based detectors. The article concludes with a discussion of the remaining challenges and future perspectives.

Abstract Molecular doping is often used in organic semiconductors to tune their (opto)electronic properties. Despite its versatility, however, its application in organic photovoltaics (OPVs) remains limited and restricted to p‐type dopants. In an effort to control the charge transport within the bulk‐heterojunction (BHJ) of OPVs, the n‐type dopant benzyl viologen (BV) is incorporated in a BHJ composed of the donor polymer PM6 and the small‐molecule acceptor IT‐4F. The power conversion efficiency (PCE) of the cells is found to increase from 13.2% to 14.4% upon addition of 0.004 wt% BV. Analysis of the photoactive materials and devices reveals that BV acts simultaneously as n‐type dopant and microstructure modifier for the BHJ. Under optimal BV concentrations, these synergistic effects result in balanced hole and electron mobilities, higher absorption coefficients and increased charge‐carrier density within the BHJ, while significantly extending the cells' shelf‐lifetime. The n‐type doping strategy is applied to five additional BHJ systems, for which similarly remarkable performance improvements are obtained. OPVs of particular interest are based on the ternary PM6:Y6:PC71BM:BV(0.004 wt%) blend for which a maximum PCE of 17.1%, is obtained. The effectiveness of the n‐doping strategy highlights electron transport in NFA‐based OPVs as being a key issue.

Functionalisation of conjugated polymers is essential for performance in many applications, yet there are limited approaches to achieve this. Here the authors developed a method for the direct postpolymerisation modification of the aromatic backbone of conjugated polymers and used them to create multifunctional semiconducting nanoparticles.

Adhesion lithography enables coplanar nanogap electrode fabrication and allows for the realisation of nanoscale electronics manufacturing A collaborative team led by Thomas Anthopoulos from King Abdullah University of Science and Technology demonstrated a novel method for patterning coplanar electrodes with inter-electrode distances of less than 15 nm and arbitrarily large aspect ratios. This facile manufacturing method, called adhesion lithography, was used to fabricate a series of functional nanoscale electronic devices on various substrates. These flexible electronic devices, which are technologically relevant, included self-aligned-gate transistors, radio frequency diodes and rectifying circuits, multi-colour organic light-emitting diodes and multilevel non-volatile memory devices. Given its versatility in the fabrication of functional electronic devices and its solution-processing compatibility with a range of semiconductors and substrate materials, adhesion lithography is an attractive processing method for the high-throughput manufacture of large-scale flexible electronics at the nanoscale.

Organic electronics: Conjugated polymer doped by fluoride anion Fluoride anions have been confirmed to be capable of n-dope the organic semiconductors and thus provide more possibilities in molecular doping. A collaborative team led by Martin Heeney from Imperial College London shows an effective n-doping effect in P(NDI2OD-T2) polymer by the Lewis basic anion fluoride. The formation of radical anions is confirmed by electron paramagnetic resonance and absorption spectroscopy. Furthermore, the doping effect is verified with the improved characteristics of the thin film transistors such as reduced injection barrier, contact resistance and hysteresis. This anion doping method can be generalised to other halide anions, thus overcoming the problem of poor stability for the conventional ‘charge transfer’ doping. It opens up new opportunities for simple solution processed doping strategies and optimisation of organic electronic devices.

Abstract The reported power conversion efficiencies (PCEs) of nonfullerene acceptor (NFA) based organic photovoltaics (OPVs) now exceed 14% and 17% for single‐junction and two‐terminal tandem cells, respectively. However, increasing the PCE further requires an improved understanding of the factors limiting the device efficiency. Here, the efficiency limits of single‐junction and two‐terminal tandem NFA‐based OPV cells are examined with the aid of a numerical device simulator that takes into account the optical properties of the active material(s), charge recombination effects, and the hole and electron mobilities in the active layer of the device. The simulations reveal that single‐junction NFA OPVs can potentially reach PCE values in excess of 18% with mobility values readily achievable in existing material systems. Furthermore, it is found that balanced electron and hole mobilities of >10−3 cm2 V−1 s−1 in combination with low nongeminate recombination rate constants of 10−12 cm3 s−1 could lead to PCE values in excess of 20% and 25% for single‐junction and two‐terminal tandem OPV cells, respectively. This analysis provides the first tangible description of the practical performance targets and useful design rules for single‐junction and tandem OPVs based on NFA materials, emphasizing the need for developing new material systems that combine these desired characteristics.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

We report the effect of bias stress on the drain current and threshold voltage of n-channel thin-film transistors based on solution processed In _2 O _3 layers. Application of a positive gate bias for variable time-periods led to displacements of the transfer curves in the positive gate bias direction. On switching off the gate bias, the transfer curves returned close to their pre-stress state on a timescale similar to that when the gate bias was switched on. The time dependence of the threshold voltage shift is described well by a stretched-exponential model. The temporal behaviour of the threshold voltage shifts is consistent with charge trapping as the dominant effect, although some defect formation cannot be ruled out.

The quality of the gate dielectric/semiconductor interface in thin-film transistors (TFTs) is known to determine the optimum operating characteristics attainable. As a result in recent years the development of methodologies that aim to improve the channel interface quality has become a priority. Herein, we study the impact of the surface morphology of three solution-processed high-k metal oxide dielectrics, namely AlOx, HfOx, and ZrOx, on the operating characteristics of In2O3 TFTs. Six different dielectric configurations were produced via single or double-step spin-casting of the various precursor formulations. All layers exhibited high areal capacitance in the range of 200 to 575 nF/cm2, hence proving suitable, for application in low-voltage n-channel In2O3 TFTs. Study of the surface topography of the various layers indicates that double spin-cast dielectrics exhibit consistently smoother layer surfaces and yield TFTs with improved operating characteristics manifested, primarily, as an increase in the electron mobility (µ). To this end, µ is found to increase from 1 to 2 cm2/Vs for AlOx, 1.8 to 6.4 cm2/Vs for HfOx, and 2.8 to 18.7 cm2/Vs for ZrOx-based In2O3 TFTs utilizing single and double-layer dielectric, respectively. The proposed method is simple and potentially applicable to other metal oxide dielectrics and semiconductors.