In this study, the effect of electrochemical etching time on the layer thickness, electrical, optical, and physical properties of fluorine-doped tin oxide (FTO) films are reported. The electrochemical etching was carried out for various durations, up to 40 min, using an electrolyte composed of zinc acetate dihydrate dissolved in hydrochloric acid. The etching kinetics, which are defined by the gradual decrease in layer thickness, were thoroughly examined and correlated to the material's electrical, optical, and wetting properties as well as surface chemistry. Surface passivation progressively impedes FTO dissolution, causing the etching rate to decrease exponentially. During the first 5 min of FTO etching, the sheet resistivity and surface energy increased from 13.2 to 109.0 Omega/square and from 27.4 to 29.3 mN/m, respectively, accompanied by a gradual increase in charge-transfer resistance. This indicates the need of an optimized etching time that balances electrical, optical, and surface properties. A detailed analysis of FTO's optical characteristics at various etching periods was conducted. The gradual alterations in the FTO surface chemistry and surface-related characteristics that were dependent on the etching time were primarily responsible for the observed changes in the physical, electrical, wetting, and optical properties. Additionally, a stronger surface-related influence on the charge carrier dynamics and recombination in the perovskite layer was demonstrated by the exponential decline in photoluminescence intensity of the MAPbI3 films on the etched FTO substrates with increasing etching time. This study provides a deeper understanding of the electrochemical etching of FTO and highlights the potential for enhancing its structural, electrical, and wetting properties to improve performance in optoelectronic devices.

In this study, we show that hexadecyl palmitate and cholesterol, two naturally occurring small molecule aliphatics, are suitable dielectrics for organic field effect transistors (OFETs). We provide a comprehensive description of their material characteristics, processability, and film-forming capabilities, as well as surface characterization and dielectric analysis. We finally employ them for the fabrication of organic field effect transistors, employing two traditional organic semiconductors, pentacene and fullerene, C60. We demonstrate that most OFETs can function with operating voltage windows as low as 1 V, and driving voltages as low as 10 mV, when these materials solubilized in chloroform, are fabricated utilizing blade coating technique.

ABSTRACT The growing demand for sustainable diagnostic devices has shifted attention toward biodegradable choices in both material and substrate design. Recent advances in wood‐ and lignin‐derived materials have enabled a growing class of sustainable electronic and bioelectronic systems, often referred to as ‘wood‐based bioelectronics’. Within this context, the present work contributes a distinct materials and device strategy by integrating PEDOT:Lignosulfonate as an active mixed ionic–electronic channel material in organic electrochemical transistors (OECTs) fabricated on biodegradable paper substrates. The PEDOT:LigS biocomposite was synthesized via chemical oxidative polymerization using various oxidants. The thin films of the resulting biocomposites exhibited good electrical conductivity of up to 1.1 S cm−1, along with biocompatibility confirmed for L929 cells by following ISO 10993 standard protocol conditions. Conventional OECTs fabricated with PEDOT:LigS showed transconductance values of up to 12.9 mS. Replacing glass substrates with photographic paper enabled the fabrication of degradable OECT devices, revealing a material weight loss of 85% after 43 days in soil. These results highlight the potential of bio‐based materials for more sustainable wood‐based bioelectronics.

Organic electrochemical transistors (OECTs) enable low-voltage amplification of ionic signals directly in aqueous media, making them potential platforms for bioelectronic interfaces, neuromorphic circuits, and biosensors. Despite significant progress, most high-performance OECTs still rely on PEDOT:PSS, where the acidic, PSS-rich formulation and large excess of insulating polyanion can limit electronic transport and raise concerns regarding long-term stability and biocompatibility. In this work, we build on our previously reported PSS-free PEDOT colloids sterically stabilized by poly(vinyl alcohol) (PVA) and investigate this water-processable dispersion as an organic mixed ionic-electronic conductor (OMIEC) channel material for OECTs. The colloid, synthesized via oxidative polymerization of EDOT in water in the presence of neutral polymer PVA, yields highly stable dispersions that form smooth, conductive thin films suitable for device fabrication. Implemented as OECT channels, these PSS-free PEDOT:NO3/PVA films exhibit reproducible mixed ionic-electronic transport under aqueous operation with maximum transconductance values exceeding 10 mS. To the best of our knowledge, this is the first demonstration that a PVA-stabilized, PSS-free PEDOT colloid processed entirely from water can operate as an active OECT channel material, establishing a versatile route to neutral-polymer-stabilized, water-processable OMIECs for future soft and sustainable bioelectronic applications.

Indigo, a dye with historical significance, is being investigated as an organic semiconductor for use in organic electronic devices. However, indigo and its derivatives exhibit poor solubility during device processing. In this article, we synthesized symmetrical dibromo, diphenyl, and dinaphthalenyl indigo derivatives (compounds InBr (also known as Tyrian purple), InPh, and InNap). For the first time, we show the synthesis of dihaloindigo by direct halogenation of indigo. To enhance solubility during processing, thermo-cleavable tert-butoxycarbonyl (Boc) groups were incorporated. A post-deposition thermal treatment process is then described, enabling the removal of Boc groups and the production of semiconductor films. The synthesized compounds (InBr, InPh, and InNap) have an optical band gap of 1.6-1.8 eV, while the Boc-protected compounds exhibit a band gap of similar to 2.13 eV. Physical vapor-deposited (PVD) compounds showed p-type charge transport in organic field-effect transistors (OFETs) with a hole mobility of up to 2.2 & times; 10(-2) cm(2)V(-1)s(-1). Moreover, the dibromo derivative InBr showed ambipolar charge transport, featuring electron mobility of up to 1.1 & times; 10(-3) cm(2)V(-1)s(-1) in an electron transport-enhancing setup. The compound InNap, contrary to the usual experience, retained the form of a homogenous film even after the thermal treatment.

Reliable determination of ionization energies (IE) and electron affinities (EA) is essential for understanding energy-level alignment in solar cells. Here, we benchmark cyclic voltammetry (CV) and electrochemical voltage spectroscopy (EVS) for IE and EA determination against ultraviolet photoelectron spectroscopy (UPS) for IE and the combination of UPS and photothermal deflection spectroscopy (PDS) for EA. The investigated materials are FA 0.8 Cs 0.2 Pb ( I 1 - y Br y ) 3 perovskite thin films with varying bromide fraction y = 0-1. Onset potentials and energies were reproducibly extracted using tangent-based scripts, avoiding data smoothing and minimizing user bias. The optical band gap scales linearly with bromide fraction. The IE remains approximately constant up to y = 0.4 (EVS) and y = 0.6 (CV), increasing upon further substitution. All investigated methods consistently reveal a decrease in EA with increasing bromide content. Finally, we highlight practical considerations relevant to the application of EC methods and UPS.

Perovskite solar cells (PSCs) continue to attract considerable research interest due to their high power conversion efficiencies and compatibility with low temperature solution processing. In inverted PSC architectures, the inclusion of a buffer layer between the electron transport layer (ETL) and the metal electrode is essential for optimizing charge extraction and minimizing interfacial recombination losses. Bathocuproine (BCP) is commonly employed for this purpose; however, its influence on interfacial electronic properties and long term device performance remains an area of ongoing study. In this work, we explore a modified buffer layer approach by introducing sodium casinate from casein, a naturally occurring phosphoprotein with known affinity for metal ions, into the BCP layer. The addition of sodium caseinate was found to improve interfacial quality, lower trap state density, and enhance the electrical conductivity of the buffer layer. As a result, the power conversion efficiency (PCE) of the devices increased from 14.4% to 16.5%, accompanied by improved long term and operational stability. These findings highlight the potential of casein as a multifunctional additive for interface engineering in perovskite photovoltaics.

We demonstrate in this work the practical use of naturally extracted waxes of plant and animal origin, i.e., beeswax, carnauba wax, rice bran wax, lanolin wax, and two shellac waxes as dielectrics in organic field effect transistors (OFETs). We present a thorough characterization of their material properties, processability and film forming characteristic, surface characterization, dielectric investigation and the fabrication of field effect transistors with two classic organic semiconductors, i.e., pentacene and fullerene C60. We show that operating voltages as low as 1 V are possible for all the OFETs using blade coating as fabrication method of waxes solubilized in their appropriate solvent, chloroform or n-octane. Although in general difficult to process in thin films, we demonstrate in this work the practical applicability of these natural waxes for electronics fabrication.

Three natural alkaloids: caffeine, theobromine and theophylline are reported for their application as dielectric layers in organic field effect transistors (OFETs) utilizing both gold and aluminum gate electrodes. After careful purification of the materials, a detailed analysis using x-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), contact angle (CA), impedance spectroscopy, amplitude modulated kelvin probe force microscope (AM-KPFM) and cyclic voltammetry (CV) is performed. OFET devices operating at typical voltages between 2 and 4 V have been fabricated with the investigated alkaloid films processed via blade coating (caffeine) or vacuum processing (theobromine and theophylline). The dielectric properties of these three alkaloids are measured in impedance spectroscopy and negligible leakage currents are observed when deposited in thin films as dielectric layers in OFETs on aluminum electrodes. There is a high tendency of these molecules to crystallize and form uneven surfaces. When the thin film forming properties are carefully controlled, organic alkaloids can be employed in applications involving implantable, transient or even edible electronics.

For the first time, an alkyl-chain free variant of polythieno[3,4-b]pyrazine (PTP) was created in a conductive state via oxidative chemical vapour deposition (oCVD). The charge transport properties of this new PTP are superior to those of the state-of-the-art ones by ten-fold with a conductivity of 0.5 S cm(-1) and the material is found in the metallic regime of the metal-insulator-transition as the conductivity is vastly independent on temperature. Herein, we investigate the chemical and physical composition of the material in order to explain this improvement and discuss the results in light of the polythiophenes produced using the same method. Using GIWAXS, we discover large crystalline features combined with smaller, highly organized assemblies and gain insight into the chain length. The chemical composition of the material is determined via XPS and FTIR and further supplemented by computational methods. We employ DFT calculations (omega B97X-V/def2-QZVP) to understand the differences between unsubstituted and alkylated PTP. The former shows stronger proclivity to form planar structures, and the conjugation is broken upon distortion. Alternatively, in the latter case, such disorder does not considerably affect the conjugation. Furthermore, we simulate the effects of doping based on XPS results and reveal the possibility of protonation, despite the low pK(a) of the materials. Furthermore, this protonation allows the materials to achieve a cis conformer despite the typical expectation suggesting the prevalence of the trans form. Molecular dynamics simulations (NPT MD) of 24 dodecamers confirm the prevalence of a trans conformer. However, at multiple occasions, trimers of the cis motif form. The simulations predict stronger charge transport in the trans conformer. However, the cis isomer exhibits relevant levels and an extremely low HOMO-LUMO difference (<0.1 eV). This indicates the possibility of high conductivities and explains the hallmarks of metallic charge transport we observe experimentally.

Three Pinaceae resins originating from trees of high industrial significance-European larch, European spruce, and Atlas cedar-were examined in this work. These resins exhibited ease of processing using ethyl alcohol solutions, exceptional film formation, and great dielectric qualities with measured breakdown fields in the range of 5-7.3 MV cm-1. Because their film surface was essentially trap-free, it was possible to fabricate organic field effect transistors that are hysteresis-free and have outstanding stability under 12-hour bias stress at working voltages below 10 V, with current retention approaching 90% of the original value and transfer curve recovery occurring within 90 minutes. These environmentally friendly materials, which are freely available, are a great option for applications aiming to produce sustainable electronics.

In this research, cobalt-doped Ni(OH)2 on a PANI-decorated NF substrate is prepared via an electrochemical method. The surface characteristics, roughness, chemical composition, and crystalline structure of the prepared materials are described using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), in that order. Further, optical characterization techniques of attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and Raman spectroscopy are used for confirmation of the polymerization of PANI. The results reveal that PANI and bimetallic oxide/hydroxide agglomerate on the bare NF's flat skeleton. The electrocatalytic performance of Co-Ni(OH)2/PANI-NF for the oxygen evolution reaction (OER) in alkaline media is carried out, and it demonstrates outstanding electrocatalytic activity, exhibiting an overpotential of 180 mV@20 mA cm-2 with a Tafel slope of 62 mV dec-1. The TOF (10-2) value is determined to be 2.49 s-1 at 1.58 V, highlighting the elevated intrinsic activity of Co-Ni(OH)2/PANI-NF in catalyzing the OER. The stability testing using chronoamperometry (CA) for 24 h to accomplish 100 mA cm-2 and cyclic voltammetry (CV) for 200 cycles with a scan rate of 5 mV s-1. The results demonstrate that the material maintains its electrochemical performance and structural integrity even after prolonged exposure to these conditions. These findings highlight that Co-Ni(OH)2/PANI-NF is an effective and promising electrocatalytic material for the OER, potentially advancing the efficiency of hydrogen production through water electrolysis.

Enzyme immobilization is regarded as a key factor for their effective utilization in various fields such as biofuel production, wastewater treatment, and biosensors. Designing new electrodes with biocompatible support matrices is essential to improve the stability in bioelectrocatalysis. Modified carbon felt electrodes were prepared and tested as bioelectrocatalyst under mild conditions - aqueous media at room temperature and basically neutral pH. Co-immobilization of dehydrogenase enzymes and neutral red (NR) dye at carbon felt electrodes was successfully achieved during electropolymerization of pyrrole in a facile one-step approach. Neutral red was incorporated to operate as a redox mediator supporting efficient electron transfer to the enzymes' active sites. Electrodes modified with alcohol dehydrogenase (ADH) have been employed to reduce acetaldehyde to ethanol in a chronoamperometic setting with Faradaic efficiency (FE) of up to 33%. By incorporating the cascade reaction with three enzymes - ADH, formate dehydrogenase, and formaldehyde dehydrogenase - an electroreduction sequence could be established to produce methanol from CO2 reaching a FE of 10%. The proposed approach shows good stability. Together with the simple implementation and application, this process is promising for employment in enzymatic electrocatalysis.

Noble metal nanoparticles are known to act as redox catalysts or cocatalysts in important reactions including water splitting, nitrogen fixation, or CO2 reduction. In case their diameter falls below about 10 nm, the literature is split between, on the one hand, reports of ever-increasing catalytic activity with decreasing diameter and, on the other hand, reports about an optimal diameter of about 3-6 nm, below which the catalytic activity decreases rapidly. In our study, we use the model reduction of ferricyanide to ferrocyanide catalyzed by gold nanoparticles to demonstrate that, determined by the oxidative counter-reaction, different dependencies of the catalytic activity on diminishing nanoparticle diameter exist. If no intermediate charge storage takes place, the catalytic activity increases monotonically roughly with the inverse of the diameter, down to 2 nm. If, however, a strong reductant is present, the nanoparticles act as an intermediate storage of electrons, so-called nanocathodes, which is compromised by Coulomb repulsion. This leads to an optimal diameter of 4-5 nm. It is the strength of this study that exactly the same batches of gold nanoparticles and the same model reduction are used so that the parameter space for the different size dependence of the catalytic activity is limited to the differences in oxidative counter-reactions.

In the field of bioelectronics, designing novel organic mixed ionic-electronic conductors (OMIECs) is crucial to overcome the limitations in terms of biocompatibility and long-term stability. Polymeric OMIECs are reported for their potential applications in implantable devices to record and stimulate biological signals. Deoxyribonucleic acid (DNA) templated PEDOT and polypyrrole are synthesized via oxidative chemical polymerization. The biocompatibility and long-term chemical stability of conductive composites PEDOT:DNA and PPy:DNA are evaluated and compared to PEDOT:PSS. To examine in vitro cytotoxicity, NIH 3T3 cells are cultured on thin-films of PEDOT:PSS and DNA-based biocomposites. The visual determination of cell morphology and adhesion are carried out by fluorescent optical microscopy and atomic force microscopy (AFM) imaging. The acute and long-term cell viability is performed by using flow cytometry. After 96 h of incubation, the cells maintain over 80% viability, retaining their morphology and adhesion properties similar to control cells on plastic or glass samples. This indicates that all tested samples demonstrate high biocompatibility. The material stability of PEDOT:DNA and PPy:DNA is investigated by integrating the materials into organic electrochemical transistors (OECTs). The results confirm an efficient ion-to-electron transduction in OECTs and long-term chemical stability after storing the materials for up to 5 years.

Organic electrochemical transistors (OECTs) have emerged as essential components in various applications, including bioelectronics, neuromorphics, sensing, and flexible electronics. Recently, efforts have been directed toward developing flexible and sustainable OECTs to enhance their integration into wearable and implantable biomedical devices. In this work, we introduce a novel PEDOT:Sacran bio-nanocomposite as a channel material for flexible and biodegradable OECTs. Sacran, a high-molecular-weight polysaccharide derived from blue-green algae, possesses exceptional ionic conductivity, water retention, and biocompatibility, making it a promising candidate for bioelectronic applications. We successfully fabricated ultrathin and flexible OECTs on poly(ethylene terephthalate) (PET) foils, achieving transconductance values up to 7.4 mS. The devices exhibited stable ion-to-electron transduction after mechanical deformation. The OECTs were further demonstrated on eco-friendly and biodegradable poly(lactic acid) (PLA) substrates, achieving a transconductance of 1.6 mS and undergoing enzymatic hydrolysis under controlled conditions. This study highlights the potential of Sacran-based conductive bio-nanocomposites in advancing sustainable bioelectronic devices.

Nowadays, hydrogen fuel is becoming more popular, and it is attracting significant attention as a sustainable and environmentally benign energy source owing to its zero emission of harmful substances and high energy density. Hydrogen generation through the electrocatalytic hydrogen evolution reaction (HER) employs economically inexpensive and self-supported electrocatalysts that hold immense potential to provide a sustainable and cost-effective fuel in the future energy scenario. A self-supported NiO@TiO2 nanofiber composite on Ti-foil is synthesized via a hydrothermal approach, and it is used as an electrocatalyst in the HER under alkaline conditions. The surface morphology, crystalline structure, and chemical composition of the electrode are analyzed by using high-resolution scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, which confirms that NiO nanoparticles are anchored to the surface of TiO2 nanofibers. Investigation of the electrocatalytic properties of the NiO@TiO2 nanofiber composite in a 1 M KOH electrolyte solution for the HER showed an overpotential of 144 mV at 10 mA cm(-2) with a Tafel slope of 152.34 mV dec(-1). The NiO that is anchored to the TiO2 nanofibers creates more catalytically active sites, which increases the surface area and enhances the HER performance. The charge transfer resistance of R-ct = 41.6 Omega is determined from the electrode kinetics analyzed by using an electrochemical impedance spectroscopy Nyquist plot. The chronopotentiometric stability test confirms that the NiO@TiO2 composite electrode shows a robust production of H-2 gas with only 7.6% potential deviation after 12 h of electrocatalytic activity. Furthermore, a Faradaic efficiency of 86% for hydrogen is achieved after 100 min of the HER. The results confirm that the NiO@TiO2 nanofiber composite is a promising candidate material for the electrocatalysis of the HER.

Organic colorants epindolidione (EPI) and quinacridone (QUI) are commercially available hydrogen-bonded semiconductor pigments. Despite their suitable properties for bioelectronic applications, their biocompatibility has not been thoroughly examined yet. In this study, thin EPI and QUI layers were applied on well plates by vacuum deposition technique followed by short and long-term in vitro biocompatibility study. In vitro testing represents a relatively fast and cheap approach, especially suitable for screening testing and prioritization of materials for further research. LIVE/DEAD assay, cell cycle analysis, adhesion and morphology of NIH 3T3 mouse fibroblasts have been investigated up to 7 days using flow cytometry and fluorescent optical microscopy. In summary, no significant differences were observed in viability, cell morphology, or attachment capabilities between control cells and cells grown on the EPI or QUI surfaces or cells cultivated in medium harvested from EPI- or QUI-coated wells. Our results suggest that both pigments are highly biocompatible. The absence of adverse biological effects of EPI and QUI together with their low cost and availability indicate their high application potential in next-generation bioelectronic devices.

Hydrogen peroxide (H2O2) is identified as a promising reagent for fuel cells, reducing the dependency on carbon-based fuels. In this work, electrochemically synthesized polymers are employed to improve the efficiency of the oxygen (O2) reduction reaction, thus producing H2O2 in an environmentally friendly way. Two aminoanthraquinones, as well as riboflavin (vitamin B2), are successfully immobilized via oxidative electropolymerization onto both glassy carbon and carbon paper. Of the investigated compounds, polyriboflavin shows a high Faradaic efficiency toward O2 reduction, even at a very low potential of only -0.1 V versus SHE. This catalytic effect is present in neutral and alkaline conditions, using both glassy carbon and carbon paper, but highly pronounced in neutral, aqueous solutions. Two aminoanthraquinones, as well as riboflavin (vitamin B2), are immobilized via oxidative electropolymerization onto both glassy carbon and carbon paper. Polyriboflavin shows a high Faradaic efficiency toward O2 reduction, even at a low potential of -0.1 V versus SHE. This catalytic effect is present in neutral and alkaline conditions.image