Abstract Light‐stimulated synaptic transistors offer a promising platform for neuromorphic computing and artificial vision by emulating biological synaptic behaviors with optical control. In this study, we demonstrate a photonic synaptic transistor based on an organic semiconductor system, exhibiting tunable excitatory postsynaptic current, paired‐pulse facilitation, and synaptic weight modulation under varying light intensities and pulse durations. The underlying mechanism is attributed to oxygen‐induced charge trapping, as confirmed by electronic structure analysis and Kelvin probe force microscopy. Furthermore, the device is integrated into an artificial neural network for delay reservoir computing, achieving high recognition accuracy in Modified National Institute of Standards and Technology digit classification. These findings highlight the potential of light‐driven neuromorphic hardware for energy‐efficient, high‐speed, and flexible artificial intelligence applications, paving the way for the development of next‐generation optical neuromorphic processors.

Electrolyte-gated organic field-effect transistors (EGOFETs) are attracting great attention for the development of low-cost and flexible sensors. However, in order to progress towards such applications, it is key to understand the stability of these devices in aqueous media and under mechanical deformation. Here, we have fabricated flexible EGOFETs based on two small molecule organic semiconductors blended with polystyrene. These materials have been printed employing a low-cost solution-based technique, obtaining large area crystalline films. The devices revealed a good EGOFET performance in terms of mobility. Finally, the devices were operated under tensile and compressive strain, observing a current increase (decrease) when a compressive (tensile) deformation was applied, revealing large gauge factors. Thus, this work shows the importance of assessing the device response under mechanical deformation when flexible EGOFET-based sensors are developed, in order to achieve a reliable response.

Exploiting the potential of curcuminoids (CCMoids) as molecular platforms, a new 3.53 nm extended system (pyACCMoid, 2) has been designed in two steps by reacting a CCMoid with amino-terminal groups (NH2-CCMoid, 1, of 1.79 nm length) with polycyclic aromatic hydrocarbon (PAH) aldehydes. CCMoid 2 contains pyrene units at both ends as anchoring groups to optimize its trapping in graphene nano-junctions created by feedback-controlled electro-burning. The measured I-V characteristics show gate-dependent behaviour at room temperature and 10 K, with increased conductance values compared to shorter CCMoids previously reported, and in agreement with DFT calculations. Our results show that the adjusted molecular design improves the conductance, as system 2 separates the conductive backbone from the anchor groups, which tend to adopt a planar configuration upon contact with the graphene electrodes. DFT calculations using Green functions of a set of different molecular conformations of 2 on graphene electrodes show a direct relationship between the units (e.g. pyrene, amide, etc.), in the molecule, through which electrons are injected and the conductance values; where the size of the spacing between the graphene electrodes contributes but is not the dominant factor, and thus, counter-intuitively the smallest spacing gives one of the lowest conductance values.

This article presents a novel plasmonic sensing platform designed for the detection of low molecular weight molecules, offering significant advancements in diagnostic applications. The platform features a periodic array of gold nanodisks on a 20 nm thin silica layer, supported by a 100 nm thick gold substrate. By leveraging the coupling between localized and propagating surface plasmon resonances, this design significantly enhances the sensitivity and specificity of molecular detection. Finite element method simulations are conducted to characterize the optical properties and reflectance response of the nanodisks array in the visible to near-infrared range. Ellipsometric analysis is performed to measure the reflectance of the sample at various angles. Additionally, scanning near-field optical microscopy in reflectance mode validates the design by revealing well-defined plasmonic hot spots and interference patterns consistent with the simulated results. The findings demonstrate the platform's effectiveness in amplifying optical signals, achieving a limit of detection of 50 μM for molecules with a molecular weight of less than 1 KDa. This high sensitivity and specificity highlight the potential of the proposed plasmonic platform to advance the development of highly sensitive sensors for low molecular weight molecules, making it a valuable tool for diagnostics and precise molecular detection.

Electronic skins (e-skins), composed of various flexible sensors, mimic the sensing functions of human skin aiming for both healthcare monitoring and prosthetics development applications. So far different multi-component e-skin devices aimed to fulfill different requirements (biocompatibility, skin adhesion, flexibility, conductivity, sensitivity towards biological stimuli and stretchability) have been reported. However, the obtaining of such devices combining all the above requirements within a single material that simplifies not only cost but specially functioning still remains a challenge. For this, catechol-based materials have attracted special attention due to their adhesive properties, compatibility and melanin-like electrical conduction. In this work, 2,3,6,7,10,11 – hexahydroxy triphenylene (HHTP) was used as catechol moiety in a typical melanin-like polymerization, resulting in a free-standing melanin-inspired film (MN-film). The obtained MN-film showcased good conductivities with dual charge carriers (electrons and ions) under different environments, i.e. pure water and buffers simulating sweat. Large biocompatibility, adhesion and conformability to skin were obtained as well, allowing to implement the film in wearable electronic on-skin devices on porcine skin. Measurements in wearable devices indicated large sensitivity towards different stimuli (strain, motion and temperature) under sweat-like conditions.

Organic field-effect transistors (OFETs) and phototransistors using blends of Ph-BTBT-10 with binding polymers are prepared. We show that tuning the nature of the polymer is a useful tool to optimise the OFET performance and photoresponsivity.

Contact resistance and charge trapping are two key obstacles, often intertwined, that negatively impact on the performance of organic field-effect transistors (OFETs) by reducing the overall device mobility and provoking a nonideal behavior. Here, we expose organic semiconductor (OSC) thin films based on blends of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT-C8) with polystyrene (PS) to (i) a CH3CN vapor annealing process, (ii) a doping I2/water procedure, and (iii) vapors of I2/CH3CN to simultaneously dope and anneal the films. After careful analysis of the OFET electrical characteristics and by performing local Kelvin probe force microscopy studies, we found that the vapor annealing process predominantly reduces interfacial shallow traps, while the chemical doping of the OSC film is responsible for the diminishment of deeper traps and promoting a significant reduction of the contact resistance. Remarkably, the devices treated with I2/CH3CN reveal ideal electrical characteristics with a low level of shallow/deep traps and a very high and almost gate-independent mobility. Hence, this work demonstrates the promising synergistic effects of performing simultaneously a solvent vapor annealing and doping procedure, which can lead to trap-free OSC films with negligible contact resistance problems.

Among the large amount of families of molecules investigated in molecular junctions (MJs), stable free organic radicals have gained an increasing attention over the last years. 1 Thanks to their open-shell electronic configuration, these molecules are paramagnetic, redox and optically active, which make them appealing species for a variety of applications. 2 Chlorinated trityl radicals, and in particular the perchlorotriphenylmethyl radicals have shown to be highly stable as active molecular units in MJs. 3 Such functional molecules have been recently covalently bound to photoactive, hydrogen-terminated silicon surfaces and the so modified surfaces have been demonstrated to function as light-triggered capacitance switches with good stability. 4 Herein, the charge transport of these systems, employing the open- and closed-shell molecules ( Rad-PTM and α H-PTM , Figure 1a), is investigated as solid-state Metal/monolayer/Semiconductor (MmS) junctions using an eutectic Gallium-Indium liquid metal as the top electrode. A characteristic diode behavior is observed which is tuned by the electronic characteristics of the organic molecule. Our results clearly indicate that the presence of the SOMO-SUMO molecular orbitals impacts on the device performance. The junction incorporating the radical shows an almost two orders of magnitude higher rectification ratio ( R = 10 4.04 ) in comparison with the non-radical one ( R = 10 2.30 ) at ± 1 V bias. Interestingly, the high stability of the fabricated MmS permits to interrogate the system under irradiation, evidencing that at the wavelength where the photon energy is close to the band gap of the radical, there is a clear enhancement of the photoresponse. 5 (1) Ratera, I.; Vidal-Gancedo, J.; Maspoch, D.; Bromley, S. T.; Crivillers, N.; Mas-Torrent, M. J. Mater. Chem. C 2021 , 9 , 10610–10623. (2) Mas-Torrent, M.; Crivillers, N.; Mugnaini, V.; Ratera, I.; Rovira, C.; Veciana, J. J. Mater. Chem. 2009 , 19 , 1691–1695. (3) Bejarano, F.; Olavarria-Contreras, I. J.; Droghetti, A.; Rungger, I.; Rudnev, A.; Gutiérrez, D.; Mas-Torrent, M.; Veciana, J.; Van Der Zant, H. S. J.; Rovira, C.; et al. J. Am. Chem. Soc. 2018 , 140 , 1691–1696. (4) De Sousa, J. A.; Bejarano, F.; Gutiérrez, D.; Leroux, Y. R.; Nowik-Boltyk, E. M.; Junghoefer, T.; Giangrisostomi, E.; Ovsyannikov, R.; Casu, M. B.; Veciana, J.; et al. Chem. Sci. 2020 , 11 , 516–524. (5) De Sousa, J. A.; Pfattner, R.; Gutiérrez, D.; Bromley, S. T.; Veciana, J.; Rovira, C.; Mas-Torrent, M.; Fabre, B.; Crivillers, N. ACS Appl. Mater. Interf ., submitted. Figure 1

Raman spectroscopy was employed to investigate nanometric thick films of the organic semiconductor 2,7Dioctyl[1]benzothieno[3,2-b][1]benzothiophene, following a comprehensive vibrational characterization of the compound condensed phases at various excitation wavelengths. UV Raman excitation enabled the characterization of the thin films, revealing that the molecular orientation at the film/air interface is characterized by a different organization and/or a high degree of disorder compared to the bulk phase. The low penetration depth of the UV Raman excitation allows for the retrieval of this information, unlike the XRD data.

A set of unique features, including large-area solution processing on flexible and stretchable substrates, make polymer semiconductors a promising material choice for a range of state-of-the-art applications in electronics, optoelectronics and sensing. Yet, an inherent weakness of polymer semiconductors remains their low dielectric constants, increasing their susceptibility toward unscreened dipoles. These dipoles are particularly prevalent at polymer-dielectric interfaces with high- k dielectrics, which are essential for the operation of devices such as low-voltage field-effect transistors. This shortcoming can be addressed by using self-assembled monolayers (SAMs) to passivate surfaces that impact charge transport. However, SAM-treatment also increases the hydrophobicity of surfaces and therefore poses a challenge for subsequent solution processing steps and complex packaging of devices. Here, we report low-voltage polymer transistors processed by spin coating of the polymer semiconductors on highly hydrophobic SAM-treated aluminum and hafnium oxide dielectrics (contact angles >100) through fine-tuning of the interfacial tension at the polymer-dielectric interface. This approach enables the processing and detailed characterization of near-amorphous (indacenodithiophene- co benzothiadiazole) as well as semicrystalline ( poly(2,5-bis(2-octyldodecyl)-3,6-di(thiophen-2-yl)diketopyrrolo[3,4-c]pyrrole-1,4-dione-alt-thieno[3,2-b]thiophen )) polymer semiconductors. We demonstrate polymer transistors that exhibit high on-currents and field-independent, charge carrier mobilities of 0.8 cm 2 V −1 s −1 at low operating voltages (<3 V).

The preparation of monolayers based on an organic radical and its diamagnetic counterpart has been pursued on hydrogen-terminated silicon surfaces. The functional monolayers have been investigated as solid-state metal/monolayer/semi-conductor (MmS) junctions showing a characteristic diode behavior which is tuned by the electronic characteristics of the organic molecule. The eutectic gallium-indium liquid metal is used as a top electrode to perform the transport measurements and the results clearly indicate that the SOMO-SUMO molecular orbitals impact the device performance. The junction incorporating the radical shows an almost two orders of magnitude higher rectification ratio (R(|J1V/J-1V|) = 104.04) in comparison with the nonradical one (R(|J1V/J-1V|) = 102.30). The high stability of the fabricated MmS allows the system to be interrogated under irradiation, evidencing that at the wavelength where the photon energy is close to the band gap of the radical there is a clear enhancement of the photoresponse. This is translated into an increase of the photosensitivity (Sph) value from 68.7 to 269.0 mA/W for the nonradical and radical based systems, respectively.

Our work examines the structural-electronic correlation of a new curcuminoid, AlkCCMoid, as a dielectric material on different substrates. For this purpose, we show a homemade sublimation method that allows the direct deposition of molecules on any type of matrix. The electronic properties of AlkCCMoid have been evaluated by measurements on single crystals, microcrystalline powder, and sublimated samples, respectively. GIWAXS studies on surfaces and XRD studies on powder have revealed the existence of polymorphs and the effect that substrates have on curcuminoid organization. We describe the dielectric nature of our system and identify how different polymorphs can affect electronic parameters such as permittivity, all corroborated by DFT calculations.

The performance of organic field-effect transistors is still severely limited by factors such as contact resistance and charge trapping. Chemical doping is considered to be a promising key enabler for improving device performance, although there is a limited number of established doping protocols as well as a lack of understanding of the doping mechanisms. Here, a very simple doping methodology based on exposing an organic semiconductor thin film to an aqueous iodine solution is reported. The doped devices exhibit enhanced device mobility, which becomes channel-length independent, a decreased threshold voltage and a reduction in the density of interfacial traps. The device OFF current is not altered, which is in agreement with the spectroscopic data that points out that no charge transfer processes are occurring. Kelvin probe force microscopy characterization of the devices under operando conditions unambiguously proves that an important reduction of the contact resistance takes place after their exposition to the iodine solution, reaching almost ohmic contact.

Composites exhibit unique synergistic properties emerging when components with different properties are combined. The tuning of the energy bandgap in the electronic structure of the material allows designing tailor-made systems with desirable mechanical, electrical, optical, and/or thermal properties. Here, we study an emergent insulator-metal transition at room temperature in bilayered (BL) thin-films comprised of polycarbonate/molecular-metal composites. Temperature-dependent resistance measurements allow monitoring of the electrical bandgap, which is in agreement with the optical bandgap extracted by optical absorption spectroscopy. The semiconductor-like properties of BL films, made with bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF or ET) α-ET2I3 (nano)microcrystals as two-dimensional molecular conductor on one side and insulator polycarbonate as a second ingredient, are attributed to an emergent phenomenon equivalent to the transition from an insulator to a metal. This made it possible to obtain semiconducting BL films with tunable electrical/optical bandgaps ranging from 0 to 2.9 eV. A remarkable aspect is the similarity close to room temperature of the thermal and mechanical properties of both composite components, making these materials ideal candidates to fabricate flexible and soft sensors for stress, pressure, and temperature aiming at applications in wearable human health care and bioelectronics.

To date, crystallization studies conducted in space laboratories, which are prohibitively costly and unsuitable to most research laboratories, have shown the valuable effects of microgravity during crystal growth and morphogenesis. Herein, an easy and highly efficient method is shown to achieve space-like experimentation conditions on Earth employing custom-made microfluidic devices to fabricate 2D porous crystalline molecular frameworks. It is confirmed that experimentation under these simulated microgravity conditions has unprecedented effects on the orientation, compactness and crack-free generation of 2D porous crystalline molecular frameworks as well as in their integration and crystal morphogenesis. It is believed that this work will provide a new "playground" to chemists, physicists, and materials scientists that desire to process unprecedented 2D functional materials and devices.

The presented work concerns the study of solution sheared organic thin film transistors based on a 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT) polymer blend.

Stefano Canossa, Elena Ferrari, Pit Sippel, Jonas K. H. Fischer, 4 Raphael Pfattner, Ruggero Frison, Matteo Masino, Marta Mas-Torrent, Peter Lunkenheimer, Concepció Rovira, and Alberto Girlando∗2, 7 EMAT, Department of Physics, University of Antwerp, 2020 Antwerp, Belgium Dipartimento di Scienze Chimiche, della Vita e della Sostenibilità Ambientale (S.C.V.S.A.) & INSTM-UdR Parma, Università di Parma, 43124 Parma, Italy Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany Tohoku Forum for Creativity, Tohoku University, 980-8577 Sendai, Japan Department of Molecular Nanoscience and Organic Materials, Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) and Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), ES-08193 Bellaterra, Spain Physik-Institut, Universität Zürich, 8057 Zürich, Switzerland Present address: Molecular Materials Group, 43124 Parma, Italy

Microgravity has proved to be an ideal condition to grow crystals. In article number 2101777, Raphael Pfattner, Tiago Sotto Mayor, Daniel Ruiz-Molina, Josep Puigmartí-Luis, and co-workers demonstrate how to generate simulated microgravity on Earth to grow 2D porous crystalline molecular frameworks such as 2D metal–organic frameworks and 2D covalent organic frameworks.

The modulation of the deposition speed in blends of diF-TES-ADT and polystyrene controls the formation of either the low-temperature or the high-temperature polymorph.

High levels of performance and stability have been demonstrated for conjugated polymer thin-film transistors in recent years, making them promising materials for flexible electronic circuits and displays. For sensing applications, however, most research efforts have been focusing on electrochemical sensing devices. Here we demonstrate a highly stable biosensing platform using polymer transistors based on the dual-gate mechanism. In this architecture a sensing signal is transduced and amplified by the capacitive coupling between a low-k bottom dielectric and a high-k ionic elastomer top dielectric that is in contact with an analyte solution. The new design exhibits a high signal amplification, high stability under bias stress in various aqueous environments, and low signal drift. Our platform, furthermore, while responding expectedly to charged analytes such as the protein bovine serum albumin, is insensitive to changes of salt concentration of the analyte solution. These features make this platform a potentially suitable tool for a variety of biosensing applications.