Doped Polymer Research Articles

A novel thin film composite forward osmosis membrane using bio-inspired polydopamine coated polyvinyl chloride substrate: Experimental and computational fluid dynamics modelling

A novel low-cost polyvinyl chloride (PVC) membrane was synthesized by phase inversion and fast and facile bio-inspired technique was used for substrate modification of a thin-film composite (TFC) forward osmosis (FO) membrane. Using DI water as feed solution (FS) and 1 M NaCl as draw solution (DS), water flux (WF) ranging from 4.15 to 15.95 LMH and reverse salt flux (RSF) ranging from 0.87 to 3.50 gMH were produced when the dope polymer solution concentration decreased from 17 to 10 wt%. Then, the substrate with 10 wt% PVC was selected for modification and the substrate was coated by dopamine (DA) solution for 1 and 3 h to enhance the membrane hydrophilicity and facilitate interfacial polymerization. Compared to the pristine membrane, the 1 h polydopamine (PDA) modified membrane displayed higher WF (18.90 LMH) and lower RSF (3.35 gMH). Whereas, for the longer coating time, WF decreased (9.70 LMH) due to the membrane surface pores blocking by the PDA layer. Finally, for understanding whether the experimental data can be supported by a theoretical model, the obtained experimental results were compared with a developed computational fluid dynamics (CFD) model and the results showed acceptable agreement with each other. The results of this work introduce a low-cost and facile approach for FO membrane fabrication by utilizing PVC polymer and PDA coating.

Assessment of the environmental impact of polymeric membrane production

Polymeric membranes are important in advanced separation technologies because of their high efficiency and low environmental impact. However, procedures for membrane production are far from sustainable and environmentally friendly. This work presents a life cycle assessment of the environmental impact of fabricating 1000 m2 of hollow fiber polymeric membranes. Membrane materials considered include the most popular fossil- and bio-based polymers in current use, i.e., polysulfones, polyvinylidene fluoride, and cellulose acetate. Solvents considered for use in polymer dope solution included polar aprotic solvents (N-Methyl-2-pyrrolidone, N, N-dimethylacetamide, and dimethylformamide) that are widely used in industry and an alternative green solvent (ethylene carbonate). The impacts of membrane production on global warming, marine ecotoxicity, human carcinogenic and non-carcinogenic toxicity, land use potential, and fossil resource scarcity were analyzed. Additionally, the impact on the sustainability and environmental cost of membrane production resulting from replacing fossil-based polymers with bio-based polymers or substituting toxic solvents with a green alternative was investigated. Hot spots in the membrane production process were identified, and measures to reduce the environmental impact of membrane production were proposed.

N-type charge transport in heavily p-doped polymers.

It is commonly assumed that charge-carrier transport in doped π-conjugated polymers is dominated by one type of charge carrier, either holes or electrons, as determined by the chemistry of the dopant. Here, through Seebeck coefficient and Hall effect measurements, we show that mobile electrons contribute substantially to charge-carrier transport in π-conjugated polymers that are heavily p-doped with strong electron acceptors. Specifically, the Seebeck coefficient of several p-doped polymers changes sign from positive to negative as the concentration of the oxidizing agents FeCl3 or NOBF4 increase, and Hall effect measurements for the same p-doped polymers reveal that electrons become the dominant delocalized charge carriers. Ultraviolet and inverse photoelectron spectroscopy measurements show that doping with oxidizing agents results in elimination of the transport gap at high doping concentrations. This approach of heavy p-type doping is demonstrated to provide a promising route to high-performance n-type organic thermoelectric materials.

Silkworm and spider silk electrospinning: a review.

Issues of fossil fuel and plastic pollution are shifting public demand toward biopolymer-based textiles. For instance, silk, which has been traditionally used during at least 5 milleniums in China, is re-emerging in research and industry with the development of high-tech spinning methods. Various arthropods, e.g. insects and arachnids, produce silky proteinic fiber of unique properties such as resistance, elasticity, stickiness and toughness, that show huge potential for biomaterial applications. Compared to synthetic analogs, silk presents advantages of low density, degradability and versatility. Electrospinning allows the creation of nonwoven mats whose pore size and structure show unprecedented characteristics at the nanometric scale, versus classical weaving methods or modern techniques such as melt blowing. Electrospinning has recently allowed to produce silk scaffolds, with applications in regenerative medicine, drug delivery, depollution and filtration. Here we review silk production by the spinning apparatus of the silkworm Bombyx mori and the spiders Aranea diadematus and Nephila Clavipes. We present the biotechnological procedures to get silk proteins, and the preparation of a spinning dope for electrospinning. We discuss silk’s mechanical properties in mats obtained from pure polymer dope and multi-composites. This review highlights the similarity between two very different yarn spinning techniques: biological and electrospinning processes.

Analysis of Organic-Inorganic Compatibility to Synthesis Defect Free Composite Membrane: A Review

Despite the excellent potential separation performance of the composite membrane, the incompatibility of organic membrane matrix with inorganic nanofiller has been remained as the major concern in producing a defect free composite membrane. Indeed, incompatibility between polymer and nanofiller caused fillers agglomeration, consequently, formed the interfacial void defect. When nanofillers are dispersed in the polymer dope, agglomeration tends to happen due to relatively large van der Waals forces of interaction. In the case of filler and polymer are not compatible, these forces will be dominant among the fillers, which caused the nanoparticles to attract to each, then induces aggregation. Such membrane defects inevitably lower the separation performances of the membrane. This review discussed the development of mixed matrix membrane, particularly on the concern of compatibility between polymer and nanofiller. Techniques to improve polymer-filler compatibility has been further discussed based on various modification and cross-linking strategies. Currently, the linker is studying experimentally to promote affinity between inorganic filler and the organic polymer. Indeed, this is time consuming and involves expensive research cost. In this review, an alternative technique using molecular dynamics (MD) simulation has also been elaborated to determine the efficiency of coupling agent to improve the matching of organic-inorganic materials, through the calculation of the molecular bonding energy. Theoretically, a multi-component system with lower energy than the total energy from its respective individual component can define as stable; hence, achieving polymer-filler compatibility.

Fine tuning the structural colours of photonic nanosheet suspensions by polymer doping.

Aqueous suspensions of nanosheets are readily obtained by exfoliating low-dimensional mineral compounds like H3Sb3P2O14. The nanosheets self-organize, at low concentration, into a periodic stack of membranes, i.e. a lamellar liquid-crystalline phase. Due to the dilution, this stack has a large period of a few hundred nanometres, it behaves as a 1-dimensional photonic material and displays structural colours. We experimentally investigated the dependence of the period on the nanosheet concentration. We theoretically showed that it cannot be explained by the usual DLVO interaction between uniform lamellae but that the particulate nature of nanosheet-laden membranes must be considered. Moreover, we observed that adding small amounts of 100 kDa poly(ethylene oxide) (PEO) decreases the period and allows tuning the colour throughout the visible range. PEO adsorbs on the nanosheets, inducing a strong reduction of the nanosheet charge. This is probably due to the Lewis-base character of the EO units of PEO that become protonated at the low pH of the system, an interpretation supported by theoretical modeling. Oddly enough, adding small amounts of 1 MDa PEO has the opposite effect of increasing the period, suggesting the presence of an additional intermembrane repulsion not yet identified. From an applied perspective, our work shows how the colours of these 1-dimensional photonic materials can easily be tuned not only by varying the nanosheet concentration (which might entail a phase transition) but also by adding PEO. From a theoretical perspective, our approach represents a necessary step towards establishing the phase diagram of aqueous suspensions of charged nanosheets.

NanoZnO Modified Polymer Electret Electrodes for Cyclic Voltammetry of Some Synthasized Anils

Preparation and characterization of pure and nano-ZnO doped PVDF-PMMA polymer blend-nanocomposites for investigating the charge storage and transfer effects have been studied. Fourier transform infrared (FTIR) was used for characterization and structure elucidation of the blended polymers. Polymer microstructure, chain conformation and polymer morphology were studied to establish the structure activity relations. Cyclic voltammetry (CV) was chosen to study the electronic properties of the modified polymers as it furnishes information as a function of an energy scan. The effectiveness of CV results from its capability of rapidly observing the redox behavior of the analyte over a wide potential range. Electrode reactions of the intermediates and the products formed during the forward scan have been studied for sulphonamide analogues of synthesized azomethines. Comparative electro activity of plain glassy carbon electrode and the PVDF-PMMA polymer blend-nanocomposite electrets modified electrode was studied.

Ultra-fast response polymer optical fiber oxygen measurement device and its preliminary experimental report on continuous dynamic change of arterial oxygen partial pressure under mechanical ventilation in living animals

Objective: We tried to implant the ultra-fast polymer optical fiber chemical oxygen sensor （POFCOS） into arterial blood vessel,connect with photoelectric conversion measurement system to record the continuous dynamic rapid changes of arterial PO2(PaO2) in whole living animals. It should be the experimental evidence for the new theory of holistic integrative physiology and medicine(HIPM) forexplain the mechanism of respiratory control and regulation in whole circusof respiration-circulation-metabolism. Methods: ①Fabrication of ultrafast POFCOS, calibration and its measuring system: The distal part of 2 m optical fiber was heated and pulled until it became a tapered tip. After cleaning and drying, the tip of 1 mm tapered optical fiber was dip-coated into the luminophore doped polymer solution, then was slowly pumped out while solvent was quickly evaporated to form an oxygen sensing tip, which was dried at room temperature for 24 hours. ②Animal experiments: Under general anesthesia and intubation, goatwas mechanically ventilated with 40%~60% oxygen. We exposed both right and left carotid arteries and the left femoral artery by skin cutting, and inserted the POFCOS directly into the arteries via indwelling catheter. The end of POFCOS were connected to the personal computer through optical fiber, excitation and detection Y-type optical fiber coupler through photoelectric conversion, so as we can realize the continuous dynamic response of living goat carotid PaO2 under mechanical ventilation. We mainly analyzed the intra-breath wave-form alternate increase and decrease of PaO2 and their time delay between lung and carotid arteries.We completes breathing control whole loop to explain the mechanism of mutual breathing and the switching of inspiration and exhalation. Results: The POFCOS has a very fast T90 response time was set 100 ms for liquid. When the heart rate of 40%~60% oxygen mechanical ventilated living goat was ~110 bpm, the PaO2 of left and right carotid artery showed a same wave-sizeup and down following with the inspiration and expiration of ventilator, with a range of up to 15 mmHg. There weresignificant noises of PaO2 change recorded in the left femoral artery. The lung-carotid artery time delay is 1.5~1.7 s after inhalation and exhalation, PaO2 at both left and right carotid arteries starts toincrease and decrease. After two-three heartbeats after the start of lung ventilation, thealternate up-down wave-form information of the arterialized pulmonary vein blood after pulmonary capillaries waspumpedby left ventricle to the position of peripheral chemoreceptors,thus realizing the whole cycle of inhalation and exhalation. It alternately interrupted inhalation, i.e. switching inhalation to exhalation, and then interrupted exhalation,i.e. switching exhalation to inhalation. Conclusion: The ultra-fast reactive implantableoxygen sensor and its measuring system can measure the physiological waveform changes of PaO2 in living animals, which can provide experimental evidence for explaining the mechanism of switching of inspiration-expiration in HIPM.

CO2/CH4 mixed gas separation using graphene oxide nanosheets embedded hollow fiber membranes: Evaluating effect of filler concentration on performance

Graphene oxide (GO) nanosheets-based composite polymeric membranes are being explored for the effective separation of gases owing to hydrophilic nature and abundant oxygen moieties on their surface that attracts the polar gases. In this study, the effect of GO nanosheets concentration on the CO2/CH4 mixed gas separation performance of polysulfone (Psf) hollow fiber mixed matrix membranes (HFMMMs) was examined. The different concentration of GO, i.e., 0.25, 0.5, and 0.75 wt% of the polymer dope solution, was used. Hollow fiber membranes (HFMs) were prepared using dry/wet quench method with water as non-solvent, and physicochemical properties were evaluated. Morphological changes were observed in the Psf/GO HFMMMs. The gas separation performance study of the HFM samples was carried out using pure CO2 and CH4 gases at 1–5 bar transmembrane pressure and 25 ± 2 °C. It was found that HFMMMs with 0.25 wt% GO nanosheets (PG25) showed 137% higher ideal CO2/CH4 selectivity than the pristine HFMs. In case of the mixed gas permeation studies using feed consisting of 50:50 vol% of CO2 and CH4, the PG25 HFMMMs showed 201% higher CO2/CH4 selectivity than that of the pristine HFMs. Moreover, the PG25 HFMMMs showed separation performance stability when they were applied for the long-term stability study. These results indicate that 0.25 wt% GO nanosheets in Psf is the optimum concentration which gives improved CO2/CH4 mixed gas separation performance.

New Membrane Materials for Energy Applications Based on 3D-Printable Ionogels

Considering the well-known, global challenges the energy economy and climate policy face, batteries and fuel cells are widely discussed for potential applications in the future due to their many benefits. There are some difficulties connected with these technologies though. For PEM-fuel cells one of the main problems is linked to their membranes. These are based on Nafion®, a sulfonated fluorocopolymer and therefore have a limited application temperature of 80 °C at ambient pressure due to dehydration and corresponding loss of conductivity at higher temperatures. [1] Due to this limit in operating temperature there is a significant need for alternative membrane materials, preferably with precise and defined size and geometry that can exhibit high ion mobilities and ionic conductivities above 100 °C.In recent years research on ionic liquids (ILs) has experienced a revival. These salts with melting points below 100 °C are promising components in energy devices such as batteries, solar or fuel cells, owing to their high thermal and electrochemical stability, non-flammability and high ionic conductivities. However, to prevent leaking and realise proper function of these devices immobilizing the IL in a matrix is necessary. [2] The resulting ionogels (IGs) then combine the characteristics of the respective IL with the useful properties of the polymer, i.e. its mechanical stability. This immobilization can be realized in three different ways: doping of polymers with the IL, polymerization of vinyl monomers in the IL, and polymerization of polymerizable ILs. [3]To obtain membrane materials with precisely controlled sizes, shapes and geometries along with the necessary performance stereolithography and 3D-printing of suitable materials are a promising method. [4]The aim of this work therefore is the synthesis and characterization of ILs for ion- and especially proton-conduction. The ionic conductivities of these compounds range between 10-2 – 10-4 S/cm at elevated temperatures. Moreover, with wide electrochemical and thermal stability windows (e. g. ΔE up to 3 V, Tg around -90 °C and Td over 200 °C (for some of them)) these ILs are promising for ion transport in fuel cell membranes above 100 °C and their properties are in addition studied under aspects of ion mobility. The immobilization of these ILs is furthermore realized via different methods, as mentioned above. The corresponding transparent and flexible IGs, in part containing high wt% of IL, display promising thermal and mechanical stability and reach ionic conductivities of up to 10-3 S/cm at elevated temperatures. This study also demonstrates successful 3D-printing and structuring of IGs, which clearly enables the design of materials with different requirements by simply adapting the size and shape.[1] A. Martinelli, A. Matic, P. Jacobsson, L. Börjesson, A. Fernicola, S. Panero, B. Scrosati, H. Ohno, J. Phys. Chem. B, 2007, 111, 12462.[2] Y.-S. Ye, J. Rick, B.-J. Hwang, J. Mater. Chem. A, 2013, 1, 2719.[3] J. Lu, F. Yan, J. Texter, Progress in Polymer Science, 2009, 34, 431.[4] K. Zehbe, A. Lange, A. Taubert, Energy Fuels, 2019, 33, 12885.

High-Performance Thin-Film Transistors Enable By Metal Oxide Semiconductor with Polyaniline Doing in the Channel Layer

Thin-film transistors(TFTs) using metal oxide-based semiconductors have attracted much attention because of their high carrier mobility, excellent optical transparency, low process temperature and solution process. In particular, indium oxide(InO x ) is capable of aqueous routes for environmentally friendly and shows excellent carrier transport due to high carrier concentrations. Despite these advantages, pristine InO x films are generally polycrystalline structures, making it difficult to apply to flexible electronics, and it is necessary to adjust the carrier density to improve stability. Moreover, such a polycrystalline thin film does not exhibit uniform threshold voltage and field-effect mobility, making it difficult to enlarge the device. To address this problems, InO x was doped with inorganic materials such as Ga, Zn, Sn and Sc. Since the thin film transistors using these amorphous metal oxide semiconductor lowers the carrier density, it adversely affects carrier mobility.In order to solve the doping problem of the conventional inorganic material that lowers the carrier mobility, we proposed solution-processed polyaniline doping in the channel layer of metal oxide semiconductors. As a result, depending on the polymer concentration inside the metal oxide semiconductor, the crystallinity of the InO x film decreases and the carrier concentration is controlled, affecting electrical properties such as field-effect mobility, on / off ratio, onset voltage and hysteresis. These results show the possible applicability to the industrial field as well as a significant meaning in improving the properties with polymer doping in the solution-processed metal oxide semiconductor at low temperatures.

Ordered arrangement of F4TCNQ anions in three-dimensionally oriented P3HT thin films

An ordered arrangement of electron-accepting molecular dopant, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), in three-dimensionally (3D) oriented poly(3-hexylthiophene) (P3HT) film was clarified. The 3D oriented P3HT thin films prepared by the friction-transfer technique were doped with F4TCNQ by dipping into an acetonitrile solution. The presence of F4TCNQ anions in the 3D oriented P3HT thin films was investigated by polarized ultraviolet/visible/near-infrared absorption spectroscopy, grazing incidence X-ray diffractometry, polarized Fourier transform infrared spectroscopy (FT-IR), and infrared p-polarized multiple-angle incidence resolution spectroscopy (pMAIRS). The F4TCNQ-doped 3D oriented P3HT films showed anisotropic properties in all characterizations. In particular, the anisotropic molecular vibrations from polarized FT-IR and pMAIRS have clearly revealed orientations of polymeric chains and molecular dopant molecules. Considering the results from several independent techniques indicated that F4TCNQ anions in the 3D oriented P3HT were orderly arranged in a 3D manner with respect to the 3D oriented P3HT such that their molecular long-axis parallel to the P3HT backbone, with in-plane molecular orientation. Additionally, the direction of the optical transition moment of the F4TCNQ anion was found to be parallel to the molecular short-axis.

Sequential Doping of Ladder-Type Conjugated Polymers for Thermally Stable n-Type Organic Conductors.

Doping of organic semiconductors is a powerful tool to optimize the performance of various organic (opto)electronic and bioelectronic devices. Despite recent advances, the low thermal stability of the electronic properties of doped polymers still represents a significant obstacle to implementing these materials into practical applications. Hence, the development of conducting doped polymers with excellent long-term stability at elevated temperatures is highly desirable. Here, we report on the sequential doping of the ladder-type polymer poly(benzimidazobenzophenanthroline) (BBL) with a benzimidazole-based dopant (i.e., N-DMBI). By combining electrical, UV–vis/infrared, X-ray diffraction, and electron paramagnetic resonance measurements, we quantitatively characterized the conductivity, Seebeck coefficient, spin density, and microstructure of the sequentially doped polymer films as a function of the thermal annealing temperature. Importantly, we observed that the electrical conductivity of N-DMBI-doped BBL remains unchanged even after 20 h of heating at 190 °C. This finding is remarkable and of particular interest for organic thermoelectrics.

Effect of polymer molecular weight on structure and performance of PVDF hollow fiber membranes prepared via TIPS process with co-extrusion of solvent using triple orifice spinneret

The co-extrusion of solvent at the outer layer of a dope solution in a thermally induced phase separation (TIPS) process has led to significant improvements in membrane characteristics, especially pure water permeability stability. This work investigates the effects of the poly (vinylidene fluoride) (PVDF) molecular weight and concentration on the characteristics of hollow fiber membranes prepared using this method. The PVDF molecular weight had little effect on the phase diagram of the PVDF/diphenyl carbonate (DPC) system, and effectively controlled the penetration depth and quantity of the extruded solvent (propylene carbonate (PC)) inside the polymer dope solution as well as the overall performance of the hollow fiber membranes. When the PVDF concentration was low, the PVDF molecular weight was crucial in controlling the penetration of the extruded solvent. For a PVDF/DPC system that led to the mainly bicontinuous structure which resulted from L-L phase separation, the penetration of the PC inside the membrane considerably changed the surface and sublayer structure from a bicontinuous structure with spherulite to a composite spherulite embedded in the bicontinuous structure and isolated spherulite structure. To obtain an appropriate membrane with considerable water permeability stability, it is necessary to choose an appropriate polymer molecular weight and concentration.

Batch and column studies using doped polymer for elimination of Sodium 4-[4-(dimethylamino) phenyl] diazenyl benzene-1-sulfonate from wastewater

ABSTRACT In the present research Polyaniline (PANI) has been prepared by chemical polymerisation using oxalic acid (OA) as a dopant. Removal of Methyl Orange (MO), (Sodium 4-{[4-(dimethylamino) phenyl] diazenyl} benzene-1-sulphonate), from wastewater, has been carried out using Oxalic acid (OA) doped Polyaniline. Breakthrough curves have been obtained from column adsorption experiments. Maximum dye adsorption was witnessed at pH 3. Four isotherm models were studied for the adsorption data and the subsequent constants have been calculated. The mean adsorption energy estimated from the D-R isotherm model has been determined as 1.5 × 104 J mol−1. Thermodynamic investigations intimated the spontaneity as well as endothermicity, with an entropy change of (79 J mol−1 K−1). Kinetic experiments divulged the adsorption of the dye by a second-order mechanism. The film diffusion mechanism was predominating at all studied temperatures. The percentage saturation for PANI column is 99.98% with the adsorption capacity of adsorbent as 8.36 mg/g. The recovery of dye has been accomplished by 0.1 N NaOH through the exhausted column. Results demonstrated PANI to be an excellent adsorbent for the eradication of the hazardous dye from textile wastewater.

Destabilization of the Nematic Phase of Clay Nanosheet Suspensions by Polymer Adsorption.

Complex aqueous mixtures comprised of swelling clays and hydrosoluble polymers naturally occur in soils and play a major role in pedogenesis. They are also very often used for formulating oil-well drilling fluids, paints, and personal-care products. The suspensions of some natural clays, thanks to their large nanoparticle aspect ratio, spontaneously form nematic liquid-crystalline phases where the particles align parallel to each other, which affects their flow properties. We observed that adding small amounts of hydrosoluble polymers to these clay suspensions destabilizes the nematic phase with respect to the isotropic (disordered) phase. The polymers that we used (poly(ethylene oxide) and dextran) were too small to adopt particle-bridging conformations and small-angle X-ray scattering experiments showed that the structure of the nematic phase is not altered by polymer doping. However, the adsorption isotherm shows that the macromolecules adsorb onto the clay nanosheets, effectively coating them with a polymer layer. Our extension of Onsager's theory for polymer-coated platelets properly captures the experimental phase diagram and shows how the nematic phase destabilization can be due to the polymer adsorbing more on the platelet faces than at the rim. Because the flow properties of the nematic phase are very different from those of the isotropic phase, the presence or absence of the former phase is an important factor to be determined and considered to explain the rheological behavior of these complex systems.

Thermal, Structural, Optical and Electrical Conductivity studies of pure and Mn2+ doped PVP films

Pure and Mn2+ ions doped (1 to 5 mol%) PVP polymer electrolytes were prepared by solution casting method by using double distilled water as a solvent. Thermogravimetric curves of the pure and Mn2+ doped polymer films show three distinct steps of weight loss. The Enhanced amorphous nature of PVP polymer film due to doping has been identified from X-ray diffraction analysis. SEM images appear the smoothest, uniform and homogenous surface, suggesting a good ordering structure. The optical band gaps of the films showed a decreasing trend with increasing dopant concentration. The FTIR spectra confirmed the complexation between the Mn2+ ions and the host polymer in terms of changes in intensity and certain bands position. The conductivity data, showed that 5 mol% Mn2+ doped PVP polymer electrolyte had shown maximum ionic conductivity of 3.21 × 10−8 S/cm at room temperature. From all the characterization results, 5mol% of Mn2+ ion-doped PVP polymer electrolyte exhibits better properties which are more suitable for fabricating solid-state batteries and other electrochemical devices.

Permanent Electrochemical Doping of Quantum Dots and Semiconductor Polymers

AbstractArguably the most controllable way to control the charge density in various semiconductors, is by electrochemical doping. However, electrochemically injected charges usually disappear within minutes to hours, which is why this technique is not yet used to make semiconductor devices. In this manuscript, electrochemical doping of different semiconductor films (ZnO Quantum Dots (QDs), PbS QDs, and P3DT) is investigated in various high melting‐point nitrile‐based solvents. It is shown that by charging the semiconductors at elevated temperatures, then cooling down to room temperature where these solvents are frozen, the doping stability increases immensely. Measurements performed in cyanoacetamide show that ion transport is entirely halted at room temperature, and that the n‐type conductivity is stable for days, and only drops marginally (≈10%) in several weeks. For p‐doped P3DT films, the conductivity is even completely stable during the entire 76 days of the measurement. In an ambient atmosphere, the p‐type doping is stable, while the n‐type doping disappears in several hours, as electrons react with molecular oxygen. Finally, a pn‐junction diode made of a PbS QD film is demonstrated. These results highlight the possibility of using solidified electrolytes for electrochemical doping and for obtaining semiconductor devices wherein the doping density is controlled electrochemically.

Effect of Sb doping and polyvinylpyrrolidone on the mesoporous TiO2 photoanodes for Sb2Se3 sensitized solar cells

Abstract Mesoporous-TiO2:Sb layers were developed by sol-gel and spin-coating techniques for their application as photoanodes in SSSCs. The effect of Sb doping (4 mol%) and PVP loading (0.2-0.4 g) on the optical, structural, morphological, and chemical properties were studied. SEM results showed that the morphology, porosity, and particle size in the mp-TiO2:Sb depend on the amount of polymer and Sb doping. In particular, the doping decreases the porosity and particle size. XRD patterns showed well-defined reflections resembling the anatase crystalline structure. The crystallite size was of 22.61 and 16.27 nm for the undoped layers with 0.2 and 0.4 of PVP, which decreased to 17.69 and 7.93 nm for the doped ones. It was not observed the presence of Sb2O3 or Sb metallic, indicating Sb ions were inserted in the TiO2 lattice by substitution of Ti ions. Analysis of XPS spectra showed the presence of Ti4+, O2-, and Sb3+ in the mp-TiO2:Sb layers. The optical bandgaps of the mp-TiO2:Sb were in the range of 3.14-3.33 eV. The evaluation of the mp-TiO2:Sb layers as photoanodes in the Sb2Se3-sensitized solar cells gives a Voc of 261 mV, a Jsc of 3.92 mA/cm2, and a PCE of 0.71%.

Broadband dielectric spectroscopy of BMPTFSI ionic liquid doped solid-state polymer electrolytes: Coupled ion transport and dielectric relaxation mechanism

Broadband dielectric spectroscopy has been used to explore the charge carrier transport and relaxation mechanisms in different compositions of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide doped poly(methylmethacrylate)-lithium bis(trifluoromethylsulfonyl)imide based solid polymer electrolytes. The free ion diffusivity and number density, which are directly linked with ion transport in ionic liquid based polymer electrolytes, are analyzed following the model of electrode polarization proposed by Macdonald–Trukhan. We have analyzed broadband dielectric spectra in terms of complex electric modulus formalism using two theoretical approaches such as Havrilliak–Negami and Kohlrausch–Williams–Watts functions. It has been observed that charge carrier diffusivity and dielectric relaxation time are strongly temperature dependent, following Vogel–Tammann–Fulcher behavior. It is also evident from the values of stretched exponent β that the relaxation behavior is highly non-exponential in these ionic liquid doped polymer electrolytes.