Organic Electronics

Contact effects in organic thin film transistors (OTFTs) remain an important problem to be solved in these devices. Therefore, the correct physio-chemical modeling of the contact regions in OTFTs is necessary. In this work, a standard model for the contact region of OTFTs is proposed. It is a versatile model that describes the current-voltage characteristics of different kinds of contacts. It reproduces the behavior of Schottky barrier or space-charge limited contacts. It is a simple unified model since only a single parameter is necessary in order to distinguish between both kinds of contacts. The model is easily integrated in a generic compact model for the current-voltage characteristics of OTFTs. The resulting compact model, used in combination with an evolutionary parameter extraction procedure, allows to extract the intrinsic parameters and the current-voltage curves at the contact of single short-channel transistors. There is no need to use transistors with multiple channel lengths to accurately characterize the contact region or the active channel of the transistor. The model is tested with published experimental data of OTFTs with Schottky barrier or space-charge limited contacts. Finally, the method has been used as a diagnostic tool to analyze how an ammonia sensor reacts to different concentrations of the ammonia gas. Interestingly, alterations in the contact region have been detected when the gas concentration varies, transforming the space-charge limited contact of a pristine OTFT into a Schottky barrier contact under the exposure of gas.

In this work, the topic of the detrimental contact effects in organic thin-film transistors (OTFTs) is revisited. In this case, contact effects are considered as a tool to enhance the characterization procedures of OTFTs, achieving more accurate values for the fundamental parameters of the transistor threshold voltage, carrier mobility and on-off current ratio. The contact region is also seen as a fundamental part of the device which is sensitive to physical, chemical and fabrication variables. A compact model for OTFTs, which includes the effects of the contacts, and a recent proposal of an associated evolutionary parameter extraction procedure are reviewed. Both the model and the procedure are used to assess the effect of the annealing temperature on a nickel-1,4,8,11,15,18,22,25-octakis(hexyl)phthalocyanine (NiPc6)-based OTFT. A review of the importance of phthalocyanines in organic electronics is also provided. The characterization of the contact region in NiPc6 OTFTs complement...

flat-panel displays and lighting applications, organic light emitting diodes (OLEDs) have been widely used because of their efficient light emission, low-cost manufacturing and flexibility. The electrons and holes injected from the anode and cathode, respectively, form a tightly bound exciton as they meet at a molecule in organic layer. Excitons occur as spin singlets or triplets and the ratio between singlet and triplet excitons formed is 1:3 based on spin degeneracy. The internal quantum efficiency (IQE) of fluorescent-based OLEDs is limited 25% because only singlet excitons contribute the light emission. To overcome this limitation, thermally activated delayed fluorescent (TADF) materials have been introduced in the field of OLEDs. The exchange splitting between the singlet and triplet states of two-component exciplex systems is comparable to the thermal energy in TADF materials, whereas it is usually much larger in excitons. Reverse intersystem crossing occurs from triplet to singlet exciplex state, and this improves the IQE. An applied small magnetic field can change the spin dynamics of recombination in TADF blends. In this study, magnetic field effects on both excitonic and exciplex OLEDs will be presented and comparison similarities and differences will be made.

The excellent mechanical flexibility of organic electronic devices is expected to open up a range of new application opportunities in electronics, such as flexible displays, robotic sensors, and biological and medical electronic applications. However, one of the major remaining issues for organic devices is their instability, especially their thermal instability, because low melting temperatures and large thermal expansion coefficients of organic materials cause thermal degradation. Here we demonstrate the fabrication of flexible thin-film transistors with excellent thermal stability and their viability for biomedical sterilization processes. The organic thin-film transistors comprise a high-mobility organic semiconductor, dinaphtho[2,3-b:2′,3′-f]thieno [3,2-b]thiophene, and thin gate dielectrics comprising a 2-nm-thick self-assembled monolayer and a 4-nm-thick aluminium oxide layer. The transistors exhibit a mobility of 1.2 cm 2 V -1 s -1 within a 2 V operation and are stable even after exposure to conditions typically used for medical sterilization.

Spintronics is an emerging field of basic and applied research in physics and engineering that aims to exploit the role played by electron spin in solid state materials. It involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. Spintronic devices make use of spin properties instead of, or in addition to electron charge to carry information, thereby offering opportunities for novel micro and nanoelectronic devices. Spin relaxation and spin transport in metals and semiconductors are of fundamental research interest not only for being basic solid state physics issues, but also for the already demonstrated potential these phenomena have in electronic technology. This article reviews the background and current status of this subject, and also some of the applications of spintronics.

The integration of gas sensor components into smart phones, tablets, and wrist watches will revolutionize the environmental health and safety industry by providing individuals the ability to detect harmful chemicals and pollutants in the environment using always-on hand-held devices. However, in order for this goal to be achieved the fabrication of gas sensors and, more precisely, the deposition of gas sensing metal-oxide materials, must be performed using a cost-effective technique which is integrable in the full CMOS sequence [1]. A sensor array requires a combination of MEMS and CMOS analog and digital circuitry in order to generate a useful product, as shown in Fig. 1.

Facile fabrication of large area (> 20 long and > 2 cm wide) uniform and oriented thin films of a variety of conjugated polymers (CPs) with minimal material wastage been successfully demonstrated using our newly developed ribbon-shaped floating film transfer method (FTM). Under an identical film fabrication conditions of FTM like hydrophilic liquid substrate consisted of ethylene glycol and glycerol (3:1), temperature of 60 o C and polymer concentration 1% (w/w) in chloroform, order molecular orientation was found to be PQT-C12>F8T2>NR-P3HT>PBTTT-C14>PTB7. Depending on the nature of polymeric backbone, CPs exhibited differentia optical anisotropies in their oriented thin films, which was explained in terms of nature and rigidity of polymeric chains in the light of persistent length. Organic field effect transistors fabricated using these CPs exhibited clear p-type behavior and anisotropic charge transport. Amongst various CPs used, PQT-C12 not only exhibits highest optical anisotropy (DR = 5.1) but also highest anisotropic

An effective approach for tuning the electronic characteristics of polymer-based organic fieldeffect transistors (OFETs) consisted of Poly(3-hexylthiophene) (P3HT) doped with 7,7,8,8tetracyanoquinodimethane (TCNQ) and depleting layer formed by Al-coating is being reported. Doping of P3HT was employed to accumulate and tune the carrier concentration while implementation of depletion layer leads to reduce the channel conductance. It has been demonstrated that on-currents in the OFETs were enhanced with the extent of TCNQ doping from 0% to 20% in the P3HT. Upon introduction of a thin layer of Al led to the formation of a depletion region resulting in to further decrease in the off-state current along with the improvement in the subthreshold characteristics. These two procedures, thus, provide counter-

1 Laboratory of Organic Electronics, Department of Science and Technology (ITN), Linköping University, SE-601 74 Norrköping, Sweden 2 Terahertz Materials Analysis Center (THeMAC), Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden 3 Center for III-Nitride Technology, C3NiT-Janzèn, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden 4 RISE Research Institutes of Sweden, Bioand Organic Electronics, Bredgatan 35, SE-602 21 Norrköping, Sweden * Correspondence: magnus.jonsson@liu.se

A high-performance nitrogen doped graphene quantum dots (GQDs)/all-inorganic (CsPbBr 3 ) perovskite nanocrystals (NCs) heterostructure photodetector was fabricated on a quartz substrate, using the low cost spin coating technique followed by hot plate annealing. The GQDs/CsPbBr 3 NCs heterostructure photodetector exhibits a high overall performance with a photoresponsivity of 0.24 AW -1 , on/off ratio of 7.2 × 10 4 , and specific detectivity of up to 2.5 × 10 12 Jones. The on/off ratio of the hybrid device was improved by almost ten orders of magnitude, and the photoresponsivity was enhanced almost three times compared to the single layer perovskite NCs photodetector. The performance enhancement of the hybrid device was due to its highly efficient carrier separation at the GQDs/CsPbBr 3 NCs interface. This results from the coupling of the GQDs layer, which efficiently extracts and transports the photogenerated carriers, with the CsPbBr 3 NCs layer, which has a large absorption coefficient and high quantum efficiency. The interfacial charge transfer from the CsPbBr 3 NCs to the GQDs layer was demonstrated by the quenching in the photoluminescence (PL) spectra, and the fast-average decay time in the time-resolved photoluminescence (Trpl) spectra of the hybrid photodetector. Moreover, the performance-enhancement mechanism of the hybrid GQDs/CsPbBr 3 photodetector was elucidated by analyzing the band alignment of the GQDs and CsPbBr 3 under laser illumination.

A high-performance nitrogen doped graphene quantum dots (GQDs)/all-inorganic (CsPbBr 3 ) perovskite nanocrystals (NCs) heterostructure photodetector was fabricated on a quartz substrate, using the low cost spin coating technique followed by hot plate annealing. The GQDs/CsPbBr 3 NCs heterostructure photodetector exhibits a high overall performance with a photoresponsivity of 0.24 AW -1 , on/off ratio of 7.2 × 10 4 , and specific detectivity of up to 2.5 × 10 12 Jones. The on/off ratio of the hybrid device was improved by almost ten orders of magnitude, and the photoresponsivity was enhanced almost three times compared to the single layer perovskite NCs photodetector. The performance enhancement of the hybrid device was due to its highly efficient carrier separation at the GQDs/CsPbBr 3 NCs interface. This results from the coupling of the GQDs layer, which efficiently extracts and transports the photogenerated carriers, with the CsPbBr 3 NCs layer, which has a large absorption coefficient and high quantum efficiency. The interfacial charge transfer from the CsPbBr 3 NCs to the GQDs layer was demonstrated by the quenching in the photoluminescence (PL) spectra, and the fast-average decay time in the time-resolved photoluminescence (Trpl) spectra of the hybrid photodetector. Moreover, the performance-enhancement mechanism of the hybrid GQDs/CsPbBr 3 photodetector was elucidated by analyzing the band alignment of the GQDs and CsPbBr 3 under laser illumination.

A one dimensional variable range hopping type conduction is observed in Poly (3, 4- ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS) films obtained by a spin coating technique on polyethylene naphthalate (PEN) substrate and the mechanism behind enhancement in conductivity in 3 % dimethyle sulfoxide (DMSO) doped PEDOT:PSS film is due to the phase segregation of PSS on the surface and reduction of energy barrier between the conducting grains. Enhanced conductivity of PEDOT:PSS films and transparency more than 80 % in the visible region makes PEDOT:PSS films suitable for flexible and transparent optoelectronic devices.

Among the new materials currently employed as electron donor element in active layers of organic solar cells (OSCs), PTB7 holds the best results. It has been extensively studied and now there is a search for new derivatives to improve its properties. In this work, a set of 24 polymers derived from polythieno[3,4b]-thiophene-co-benzodithiophene (PTB7) was studied theoretically, using chemical modifications in the benzodithiophene (BDT) moiety of the PTB7 monomeric units. After evaluations of the electronic and optical properties, including the open circuit voltage and exciton dissociation and recombination conditions, the results indicate that employing chlorine as substituent yields the most promising material for application in active layers together with Phenyl-C 61 -Butyric-Acid-Methyl-Ester (PCBM) as electron acceptor material.

A novel, solution-processable non-fullerene electron acceptor 9,9'- d]silole-3,7-diyl)bis (2,7-dioctyl-4-(octylamino)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone) (B3) based on dibenzosilole and naphthalenediimide building blocks was designed, synthesized, characterized and successfully used in a bulkheterojunction organic solar cells. B3 displayed excellent solubility, thermal stability and acquired electron energy levels matching with those of archetypal donor polymer poly(3hexylthiophene). Solution-processable bulk-heterojunction devices afforded 1.16% power conversion efficiency with a high fill factor of 53%. B3 is the first example in the literature using this design principle, where mild donor units at the peripheries of end-capped naphthalenediimide units tune solubility and optical energy levels simultaneously.

Bathocuproine (BCP) is a well-studied cathode interlayer in organic photovoltaic (OPV) devices, where it for standard device configurations has demonstrated improved electron extraction as well as exciton blocking properties, leading to high device efficiencies. For inverted devices, however, BCP interlayers has shown to lead to device failure, mainly due to the clustering of BCP molecules on indium tin oxide (ITO) surfaces, which is a significant problem during scale-up of the OPV devices. In this work, we introduce C70 doped BCP thin films as cathode interlayers in inverted OPV devices. We demonstrate that the interlayer forms smooth films on ITO surfaces, resulting from the introduction of C70 molecules into the BCP film, and that these films possess both improved electron extraction as well exciton blocking properties, as evidenced by electron-only devices and photoluminescence studies, respectively. Importantly, the improved cathode interlayers leads to well-functioning large a...

Two polyfluorene derivatives containing a phenazasiline moiety and an electron acceptor were synthesized by the Suzuki coupling reaction. Molecular weight analysis showed that the two polymers had approximately 14 and 9 fluorene units as well as functional groups. Since these polymers had donor-p-acceptor systems, their absorption edges were red-shifted compared to that of polyfluorene. Cyclic voltammetry experiments indicated that the

n-TPA-IFA organic material was synthesized and deposited on p-Si by spin coating method to produce n-TPA-IFA/p-Si heterojunction diode. We determined that the dielectric constant and energy band gap of TPA-IFA organic material were 3.91 and 3.37 eV by DFT/B3LYP/6-311G(d,p) method using on Gaussian 09 W, respectively, and the carrier type of TPA-IFA organic semiconductor material was also n-type at room temperature from temperature-dependent hall effect measurements. Using forward and reverse bias I-V measurements in the dark and under various light intensities, we examined the key electrical characteristics of the n-TPA-IFA/p-Si heterojunction diode, including Φ b and n . It was determined that the rectification ratio (RR) was approximately 10 4 . The reverse current's observed increasing behavior with increasing light indicates that the produced heterojunction diode can be utilized as a photodiode, detector, or sensor. The values of n, Φ b , and I o were determined using I-V data in dark as 1.34, 0.91 eV, and 7.25 9 10-12 A, respectively. On the other hand, when the n-TPA-IFA/p-Si heterojunction diode is exposed to 100 mW/cm 2 illumination, these parameters were obtained as 1.85, 0.80 eV, and 5.11 9 10-10 A, respectively. Photovoltaic parameters such as short circuit current (I sc ) and open circuit voltage (V oc ) were determined as 0.018 mV, 0.08 A and 0.050 mV, 0.29 A under 20 mW/cm2 light and 100 mW/cm2 light intensity, respectively. The photodetector properties of n-TPA-IFA/p-Si heterostructure were explored at different light intensities, and the photoresponsivity (R), photosensitivity (PS), specific detectivity ( D * ), and linear dynamic range (LDR) of the heterojunction changed with reverse voltage and light intensity. It was found that as light intensity increased, the linear dynamic range (LDR), a crucial characteristic for image sensors, increased as well (10.15 dB and 18.84 dB for 20 and 100 mW/cm 2 ).

The realization of fully solution processed multilayer polymer light‐emitting diodes (PLEDs) constitutes the pivotal point to push PLED technology to its full potential. Herein, a fully solution processed triple‐layer PLED realized by combining two different deposition strategies is presented. The approach allows a successive deposition of more than two polymeric layers without extensively redissolving already present layers. For that purpose, a poly(9,9‐dioctyl‐fluorene‐co‐N‐(4‐butylphenyl)‐diphenylamine) (TFB) layer is stabilized by a hard‐bake process as hole transport layer on top of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). As emitting layer, a deep blue emitting pyrene‐triphenylamine copolymer is deposited from toluene solution. To complete the device assembly 9,9‐bis(3‐(5′,6′‐bis(4‐(polyethylene glycol)phenyl)‐[1,1′:4′,1″‐terphenyl]‐2′‐yl)propyl)‐9′,9′‐dioctyl‐2,7‐polyfluorene (PEGPF), a novel polyfluorene‐type polymer with polar sidechains, which a...

organic electronic devices with physical properties similar to those of human epidermis are being developed. Such devices enable non-invasive coupling with the complex features of the skin surface serving for subsequent sensing tasks. Next to systems developed for humans and related diagnostic devices, methods to analyze the electrical signals generated by living plants attract increasing interest across fields from biology to engineering. Plants respond to different stimuli such as to touch, light, wounding or other stressors like drying with electrical signals. The comparison of the fast long-distance electrical communication in plants compared to the slower biochemical signaling is a great research topic in plant biology and agriculture. The electrical signals in plants originate on cellular and ionic level from a different mechanism compared to those in human and animal nerve cells (the depolarization in animal nerve cells is driven by an increased transmembrane influx of sodium ions, plant electrical signals, that is, action potentials, involve the influx of calcium and/or the efflux of chloride ions). Further understanding and correlation of plants electrical signals with their physiology is necessary as it could become a tool, for example, for better growth control and systems that can respond to plant needs with fertilizer or pesticide application and light/water administration. In addition, a different field, that tries to make use of the intrinsic functions of plants such as sensing, communication, The electrical signals in plant's physiological processes are of great interest in biology, biohybrid robotics, and sensors for interfacing the living organisms with an electronic readout and control. This paper reports on the application of conformable, self-adhering surface electrodes for the measurement and bidirectional stimulation of electrical signals in plants. The inkjet-printed poly(3,4-ethylenedioxythiophene) polystyrene sulfonate based electrodes are <3 µm thick, light-weight, soft and flexible, and can be easily and non-invasively transferred onto plant's outer organs for surface potential recordings due to their realization on tattoo transfer paper. The devices prove to be extremely versatile for analyzing electrical signals in Dionaea muscipula, Arabidopsis thaliana, and Codariocalyx motorius and for stimulating mechanical responses in D. muscipula. A benefit over traditional electrodes is the van der Waals self-adherence of the thin electrodes, their intrinsic flexibility and adaptation also on small leaves while providing excellent readout. The same electrode allows long-term multicycle measurements over at least 10 days and, moreover, straightforward recordings on fast-moving organs such as snapping fly traps and endogenously oscillating leaflets. The results confirm that self-adhering soft organic electronics are particularly suitable for plant electrical signal analysis when easy-application, self-adaptation, and long-term performance are required in plant science, biohybrid robotics, and biohybrid sensors.

As the development of nanotechnology progresses, organic electronics have gained momentum in recent years, and the production and rapid development of electronic devices based on organic semiconductors, such as organic light-emitting diodes (OLEDs), organic photovoltaic cells (OPVs), and organic field effect transistors (OFETs), among others, have excelled. Their uses extend to the fabrication of intelligent screens for televisions and portable devices, due to their flexibility and versatility. Lately, great efforts have been reported in the literature to use them in the biomedical field, such as in photodynamic therapy. In tandem, there has been considerable interest in the design of advanced materials originating from natural sources. Bacterial nanocellulose (BNC) is a natural polymer synthesized by many microorganisms, notably by non-pathogenic strains of Komagataeibacter (K. xylinus, K. hansenii, and K. rhaeticus). BNC shows distinct physical and mechanical properties, including...

Diketopyrrolopyrrole (DPP)‐based π‐conjugated copolymers with thiophene have exceptionally high electron mobilities. This paper investigates electronic properties and charge carrier mobilities of selenophene containing analogues. Two new copolymers, with alternating thiophene DPP (TDPP) and selenophene DPP (SeDPP) units, were synthesized. Two side‐chains, hexyl (Hex) and triethylene glycol (TEG) were employed, yielding polymers designated as PTDPPSeDPP‐Hex and PTDPPSeDPP‐TEG. Selenophene systems have smaller band gaps, with concomitant enhancement of the stability of the reduced state. For both polymers, ambipolar mobilities were observed in organic field‐effect transistors (OFET). Grazing incidence X‐ray diffraction (GIXD) data indicates preferential edge‐on orientation of PTDPPSeDPP‐TEG, which leads to superior charge transport properties of the TEG substituted polymer, as compared to its Hex analogue. Time‐dependent‐density functional theory (TDDFT) calculations corroborate the d...

Polyaniline emeraldine salt (PANI-ES) is a conductive polymer with promising optoelectronic properties, synthesized via chemical oxidative polymerization and confirmed in its emeraldine salt form through structural analysis. Optical characterization revealed distinct absorption bands linked to key electronic transitions, indicating semiconducting behavior. Under UV excitation, photoluminescence studies showed two main emission features corresponding to dimer and excimer states, both exhibiting large Stokes shifts and a quantum yield of 0.27. These long Stokes shifts suggest efficient energy relaxation, while the moderate quantum efficiency highlights the material's capability for light-emitting applications. The combination of tunable emission, stable optical response, and electrical conductivity positions PANI-ES as a versatile material for photonic technologies. Potential applications include organic light-emitting diodes (OLEDs), photodetectors, and optically pumped organic lasers. Overall, the study demonstrates that PANI-ES offers a favorable balance of structural stability, optical performance, and electronic properties, making it a strong candidate for integration into advanced optoelectronic and photonic devices.

Among ITO alternative, dielectric/metal/dielectric multilayer structures are one of the most often studied possible substituent. However, if their optical and electrical properties are systematically investigated it is not the same with regard to their mechanical properties. In the present manuscript we have studied the properties of ZnS/Cu/Ag/ZnS, ZnS/Cu/Ag/MO 3 (with M ¼ Mo or W) structures. With a maximum transmission of 90% and a sheet resistance of 5 U/sq the optimum structure exhibits a figure of merit of 82 10 À3 U À1 when l ¼ 600 nm. Beyond these standard measures we proceeded to the study of the mechanical properties of the multilayer structures. The inner and outer bending tests show that the ZnS/ Cu/Ag/ZnS (or MO 3 ) structures are more flexible than ITO, while their responses to scotch tests show that they exhibit a large adhesion to the substrate, glass or plastic. The scratching adhesion test puts in evidence that the adhesion to the substrate of the Ag layer is smaller than that of ZnS/Cu/Ag/ZnS, which is smaller than that of ITO. On the other hand, this test shows that the ZnS/Cu/Ag/ZnS (no cracks for L ¼ 25 N) is less brittle than ITO (cracks L ¼ 15N). Finally, when used as anode in organic solar cells, the structure ZnS/Cu/Ag/WO 3 allows achieving the best efficiency, similar to that obtained with ITO.

New metal free dianchoring organic dyes featuring A-p-D-p-D-p-A (acceptor -p bridge -donor -p bridge -donor -p bridge -acceptor) configuration have been designed incorporating fluorene and oligothiophene units and successfully synthesized. Elongating the conjugation pathway between the donor and acceptor units altered the distance between the anchoring sites besides the absorption and redox properties. These dyes exhibited broad and intense absorption when compared to the corresponding monoanchoring donor-p-acceptor congeners. Though the dye containing bithiophene unit exhibited comparatively low V oc due to low electron life time and facile back electron transfer, showed high power conversion efficiency arising from the good light-harvesting capability attributable to the intense absorption peak in the visible region and enhanced interfacial electron transfer rate. This work demonstrates that the smaller distance of separation between the anchoring units increases the insulating capacity of the molecular layer which retards the back electron transfer.

This study investigates the gate stress-induced mobility discrepancy in p-type single-crystal organic field-effect transistors (OFETs) on an octyltrichlorosilane (OTS)-modified SiO 2 /Si substrate. During measurements in atmosphere, anti-clockwise hysteresis was observed in the transfer curve, and the mobility calculated from the forward sweep was smaller than that calculated from the reverse sweep. Hysteresis has often been observed for OFETs but the mobility discrepancy has not been clearly understood. We formulated a "fast trapping vs. slow detrapping" model and suggested that the mobility values calculated from the reverse sweep represent the intrinsic property of the material. To verify the validity of this model, we investigated mobility anisotropy of an air-stable organic semiconductor, 2,7-bis(4-methoxyphenyl)benzo[b]benzo thieno [2,3-d]thiophene (DBOP-BTBT). By measuring the single-crystal OFET characteristics of many crystals with different orientations, we observed anisotropic hole mobility calculated from the reverse sweep. The mobility along the b-axis, which corresponds to the π-π stacking direction, was 13.9 cm 2 V -1 s -1 , and that along the a-axis was 6.2 cm 2 V -1 s -1 . However, we did not see clear anisotropy when mobility was calculated from the forward sweep due to a variation in the data. The threshold voltage from the reverse and the forward sweeps showed isotropic characteristics within the range from -60 to -70 V and from -50 to -60 V, respectively. These results indicate that the numbers of filled traps were different between the reverse and the forward sweeps at the interface, and confirm the validity of our model.

In this article, we reported the characterization of various molecular junctions' current-voltage characteristics (I-V curves) evolution under mechanical modulations, by employing a novel electrochemically assisted -Mechanical Controllable Break Junction (EC-MCBJ) method. For 1,4-benzenedithiol (BDT), the I-V curves measured at constant electrodes pair separation show an excellent reproducibility, indicating the feasibility of our EC-MCBJ method for fabricating molecular junctions. For ferrocene-bisvinylphenylmethyl dithiol (Fc-VPM), an anomalous type of I-V curve was observed by the particular control over the stepping motor. This phenomenon is rationalized assuming a model of atomic contact evolution with the presence of molecular junctions. To test this hypothesized model, a molecule with a longer length, 1,3-butadiyne-linked dinuclear ruthenium(II) complex (Ru-1), was implemented and the I-V curve evolution was investigated under similar circumstance. Compared to that with Fc-VPM, the observed I-V curves show close analogy and minor difference, and both of them fit the hypothesized model well. Nano Res DOI (automatically inserted by the publisher)

Imine-based semiconducting polymers based on thiophene-flanked diketopyrrolopyrrole (TDPP) are widely used to realize naturally disposable electronic devices. However, TDPP easily decomposes under mildly acidic conditions, limiting its potential for use in recyclable systems. Herein, we designed and synthesized two chemically recyclable thienoisoindigo (TII)-based polymers bearing an imine bond. These polymers were prepared from polycondensation reactions of the dialdehyde-functionalized monomer TII-(CHO) 2 with p-phenylenediamine (PD) to produce p(TII-PD) and with 2,6-naphthalenediamine (2,6ND) to produce p(TII-2,6ND), respectively. Using ultraviolet-visible-near infrared spectroscopy, nuclear magnetic resonance, and mass spectroscopy, we examined the recyclability of both polymers. Under mildly acidic conditions, the imine-based polymers fully degrade into the original TII-(CHO) 2 in as little as one day. Moreover, the recovered TII-(CHO) 2 monomer is chemically stable for up to 6 months under acidic conditions, allowing us to isolate the monomer in high yield (>90%). Using the recovered TII-(CHO) 2 monomer, we prepared recycled polymers, re-p(TII-PD) and re-p(TII-2,6ND). The recycled polymers displayed nearly the same electrical properties as the pristine polymers, with field-effect transistor mobilities in the order of 10 -2 -10 -3 cm 2 V -1 s -1 . These results demonstrate the versatility of the TII-based monomer unit for developing fully recyclable semiconducting polymers.

Four conjugated polymers (P1-P4) consisting of alternating anthracene-9,10-diyl and 1,4-phenylene building blocks connected via ethynylene as well as vinylene (P1 and P2), ethynylene-only (P3), and vinylene-only (P4) moieties, respectively, were synthesized and studied. The phenylene units in all four polymers bear 2-ethylhexyloxy side-chains to promote good solubility. The three polymers with vinylene units (P1, P2, and P4) were prepared using the Horner-Wadsworth-Emmons reaction. For the synthesis of the aryleneethynylene polymer P3, the palladium-catalyzed Sonogashira cross-coupling reaction was used. The polymers were characterized by NMR, Fourier transform infrared spectroscopy, and Raman spectroscopy. Photophysical, absorption and photoluminescence, and electrochemical properties were studied. Spectroscopic ellipsometry measurements were performed to gain more insight on the optical properties. In addition, the transport properties were investigated using admittance spectroscopy. The bulk hole mobility and its dependence on the electric field were evaluated for P1 and P2. V

great potential for use in the emerging Internet of Things (IoT) device ecosystem where multiple device nodes share information with cloud networking systems. Printed organic electronics can enable the mass production and integration of electronic functionalities using novel substrates. In particular, organic fieldeffect transistors (OFETs) are regarded as a key electronic element in integrated logic circuits found at the heart of IoT. High-performance OFETs with lowvoltage operation (<5 V) and charge carrier mobility beyond that of amorphous silicon (0.5-1 cm 2 V -1 s -1 ) have been demonstrated. Successful commercialization additionally requires spatially uniform device performance across the many devices on a substrate, including reproducibility in characteristics and environmental stability. In general, device performance is largely determined by material properties and the interfaces between the electrodes, dielectric, and semiconductor. A variety of strategies to improve OFET performance have been reported, such as development of new materials via rational molecular design, morphology control through thermal/solvent annealing and additives, molecular doping with p-/n-dopants, and interfacial -processed organic field-effect transistors (OFETs) have attracted great interest due to their potential as logic devices for bendable and flexible electronics. In relation to n-channel structures, soluble fullerene semiconductors have been widely studied. However, they have not yet met the essential requirements for commercialization, primarily because of low charge carrier mobility, immature large-scale fabrication processes, and insufficient long-term operational stability. Interfacial engineering of the carrier-injecting source/drain (S/D) electrodes has been proposed as an effective approach to improve charge injection, leading also to overall improved device characteristics. Here, it is demonstrated that a non-conjugated neutral dipolar polymer, poly(2-ethyl-2-oxazoline) (PEOz), formed as a nanodot structure on the S/D electrodes, enhances electron mobility in n-channel OFETs using a range of soluble fullerenes. Overall performance is especially notable for (C 60 -I h )[5,6] fullerene (C 60 ) and (C 70 -D 5h(6) )[5,6]fullerene (C 70 ) blend films, with an increase from 0.1 to 2.1 cm 2 V -1 s -1 . The high relative mobility and eighteen-fold improvement are attributed not only to the anticipated reduction in S/D electrode work function but also to the beneficial effects of PEOz on the formation of a face-centered-cubic C 60 :C 70 co-crystal structure within the blend films.

A 10-layer stack of bipolar gate dielectric was formed by sequential layer-by-layer deposition using pulsed radio frequency (RF) plasma polymerization of allylamine and vinyl acetic acid monomers. Due to polar groups localized at the interfaces between each consecutive layer by alternating amine (-NH 2 ) and carboxylic acid (-COOH) functional groups, a 60 nm thick multilayer structure demonstrated relatively high dielectric constant of 4.4 with extremely smooth and crack/pin-hole free surfaces. Without any post-deposition thermal annealing, a 10-layer stack of bipolar dielectric layers shows a low leakage current density ($1 Â 10 À6 A/cm 2 at 2 MV/cm) with high breakdown fields (>4 MV/cm). With a 10-layer stack of bipolar gate dielectrics, low supply voltage regioregular poly-(3hexythiophene) (P3HT) organic thin-film transistors (OTFT) were tested. P3HT OTFTs demonstrated low-voltage operation and moderate field-effect mobility up to $3.4 Â 10 À3 cm 2 / V s in the saturation region with the drain voltage a À12 V. The threshold voltage in the saturation region and on-off current ratio were measured to be +1.4 V and $1.2 Â 10 2 , respectively.

Two metals are used in resonant layers for chemical sensors based on surface plasmon resonance (SPR) -gold and silver. Gold displays higher shift of the resonance angle to changes of ambient refraction index and is chemically stable. Silver posses narrower resonance curve thus providing a higher signal/noise ratio of SPR chemical sensors, but has a poor chemical stability. A new structure of resonant metallic film based on bimetallic silver/gold layers (gold as an outer layer) is suggested. It combines advantages of both gold and silver resonant layers. Bimetallic resonant films display so high shift of resonance angle on changes of ambient refraction index as gold films, but show narrower resonance curve, thus providing a higher signal / noise ratio. Additionally, the outer gold layer protects silver against oxidation.

Oligoacenes are of interest as organic p-type semiconductors for use in electronic devices, but their use as n-type semiconductors is limited. N-Heteroacenes have been investigated as oligoacene-based n-type semiconductors due to their enhanced electron affinity. Herein, we report the synthesis, X-ray crystal structures, electrochemical, and field-effect transistor properties of TANC and BTANC.

Symmetric ultracapacitors have been fabricated considering nanometric 3-layered films made of alternated layers of poly(3,4-ethylenedioxythiophene) (external and internal layers) and polypyrrole (intermediate layer) deposited on steel uncoated and coated with octanethiol self-assembled monolayer. The highest electrochemical and capacitance parameters (i.e. electroactivity, doping level, stored charge, specific capacitance, Coulomb efficiency, energy density and power density) correspond to the ultracapacitor derived from the assembly of 3-layered films deposited on pre-treated steel. Thus, the interface separating the octanethiol monolayer and the most internal layer of the 3-layered film produces a very favorable interaction, which promotes important electrochemical benefits similar to those found for the interfaces in conventional multilayered films. Moreover, the pre-treatment of the steel electrode enhances the roughness and porosity of the film deposited on it, transmitting this effect layer-by-layer. Structural and morphological characteristics, which have been characterized using scanning electron microscopy and atomic force microscopy, have been related with the electrochemical and capacitance properties of the ultracapacitors.

Organic photovoltaic devices using P3HT: PCBM, P3HT:P3OT: PCBM as an active layer on ITO coated glass substrates were made-up and characterized. Different devices were produced of the same sample in the same conditions and the characteristics were compared with that of a standard thin film polycrystalline silicon solar cell. It was found that the device fabricated from the samples prepared improves the short circuit current (Isc) compared to the silicon solar cell. The Open circuit voltages for the binary devices were also high. But the open circuit voltages (Voc) for the ternary devices and the efficiency were lowest for the Samples. Index Terms – Organic solar cells; Spin Coating; binary P3HT-PCBM blend layer, ternary P3HT-P3OT-PCBM layer ——————————  ——————————

Potentiometric transduction is an important tool of analytical chemistry to record chemical signals, but some constraints in the miniaturization and low-cost fabrication of the reference electrode are a bottleneck in the realization of more-advanced devices such as wearable and lab-on-a-chip sensors. Here, an organic electrochemical transistor (OECT) has been designed with an alternative architecture that allows to record the potentiometric signals of gate electrodes, which have been chemically modified to obtain Ag/Ag n X interfaces (X = Cl -, Br -, I -, and S 2-), without the use of a reference electrode. When the OECT is immersed in a sample solution, it reaches an equilibrium state, because PEDOT:PSS exchanges charges with the electrolyte until its Fermi level is aligned to the one of Ag/Ag n X. The latter is controlled by X n-concentration in the solution. As a consequence, in this spontaneous process, the conductivity of PEDOT:PSS changes with the electrochemical potential of the modified gate electrode without any external bias. The sensor works by applying only a fixed drain current or drain voltage and thus the OECT sensor operates with just two terminals. It is also demonstrated that, in this configuration, gate potential values extracted from the drain current are in good agreement with the ones measured with respect to a reference electrode being perfectly correlated (linear slope equal to 1.00 ± 0.03). In the case of the sulfide anion, the OECT performance overcomes the limit represented by the Nernst equation, with a sensitivity of 0.52 V decade -1 . The presented results suggest that OECTs could be a viable option to fabricate advanced sensors based on potentiometric transduction.

The aim of this research is to achieve the highest efficiency for a dye-sensitized solar cell (DSSC) before the fabrication process. For DSSC efficiency improvement, six different optimization algorithms are used for the DSSC parameter extraction. The algorithms used are the genetic algorithm, grey wolf algorithm, dragonfly algorithm, moth flame algorithm, ant-lion algorithm, and whale algorithm, developed based on MATLAB coding. The physical parameters for the DSSC are the electron lifetime, electrode thickness, ideality factor, absorption coefficient, and diffusion coefficient. A comparative study is carried out among the six algorithms based on the highest efficiency and computational speed. Finally, a sensitivity analysis of environmental conditions (solar irradiance and temperature) and physical parameters is implemented and analyzed to simulate the DSSC performance for different values of these parameters. The DSSC parameters studied are short-circuit current density, open-circuit voltage, fill factor, and efficiency. The optimal electron lifetime is 100 ms, and the optimal thickness of the photoanode layer is 1 μm, reaching maximum efficiency equal to 11.79%.

2-Aryl-1,9-dihydrochromeno [3,2-d]imidazoles were prepared by a one-pot cascade reaction involving salicylaldehydes and arylideneaminoacetonitriles. These novel compounds were isolated in 11e95% yield after reflux in ethanol and triethylamine. A dimeric structure was also identified and partially evolved to the tricyclic product in DMSO solution, according to an evolution study by 1 H NMR spectroscopy.

A new iridium (III) complex [Ir(cpy) 2 (prz)], (cpy = 9-(pyridin-2-yl)-9H-carbazole; prz = pyrazine-2-carboxylic acid) has been synthesized and characterized. The molecular structure of [Ir(cpy) 2 (prz)] was confirmed by a single-crystal X-ray diffraction. The iridium metal center adopts a distorted octahedral structure coordinated to two cpy and one prz ligand, showing cis C-C and trans N-N chelate dispositions. The photophysical, electrochemical properties and thermal stability of the complex were investigated. The complex showed green luminescence and good electrochemical stability with high lying HOMO energy levels.

Accelerating the shift towards renewable materials and sustainable processes for printed organic electronic devices is crucial for a green circular economy. Currently, the fabrication of organic devices with competitive performances is linked to toxic petrochemical-based solvents with considerable carbon emissions. Here we show that terpene solvents obtained from renewable feedstocks can replace non-renewable environmentally hazardous solvent counterparts in the production of highly efficient organic photovoltaics (OPVs) light-emitting diodes (OLEDs) and field-effect transistors (OFETs) with on-par performances. Using a Hansen solubility ink formulation framework, we identify various terpene solvent systems and investigate effective film formation and drying mechanisms required for optimal charge transport. This approach is universal for state-of-the-art materials in OPVs, OLEDs and OFETs. We created an interactive library for green solvent selections and made it publicly available ...

In this study, various Alq 3 amorphous layers are prepared by vacuum deposition at different substrate temperatures T sub . The surface morphology, structural information, and electrical and optical properties of these as-deposited layers are studied by atomic force microscopy, X-ray diffraction, J-E curves, and photoluminescence studies, respectively. The optimum deposition conditions for Alq 3 amorphous layers with respect to T sub are also discussed.

In this paper, a detailed numerical study of the role of selected soliton distributions on the spin-dependent transport through trans-polyacetylene (PA) molecule is presented. The molecule is attached symmetrically to magnetic semi-infinite three-dimensional electrodes. Based on Su-Schrieffer-Heeger (SSH) Hamiltonian and using a generalized Green's function formalism, we calculate the spin-dependent currents, the electronic transmission and tunnelling magnetoresistance (TMR). We found that the presence of a uniform distribution of the soliton centres along the molecular chain reduced the size of the band gap of trans-PA molecule. Moreover, a sublattice of the correlated solitons as binary clusters, which are randomly distributed along the chain, can induce extended electronic states in the band gap of the molecule. In this case, the band gap of the molecule is suppressed and at lower voltages, the TMR bandwidth is narrowed. The current-voltage characteristic then shows an ohmic-like behaviour.

Since the beginnings of the electronic age, a quest for ever faster and smaller switches has been initiated, since this element is ubiquitous and foundational in any electronic circuit to regulate the flow of current. Mott insulators are promising candidates to meet this need as they undergo extremely fast resistive switching under electric field. However the mechanism of this transition is still under debate. Our spatially-resolved µ-XRD imaging experiments carried out on the prototypal Mott insulator (V0.95Cr0.05)2O3 show that the resistive switching is associated with the creation of a conducting filamentary path consisting in an isostructural compressed phase without any chemical nor symmetry change. This clearly evidences that the resistive switching mechanism is inherited from the bandwidth-controlled Mott transition. This discovery might hence ease the development of a new branch of electronics dubbed Mottronics.

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