Control of Thickness of PEDOT Electrodeposits on Glass/ITO Electrodes from Organic Solutions and its Use as Anode in Organic Solar Cells

AbstractPoly-ethylendioxythiophene (PEDOT) was electropolymerized from the monomer EDOT in acetonitrile (ACN) containing Bu4N+ClO4-, BF4- or PF6- ions as supporting electrolyte. The electrode used was transparent electrodes (Glass/ITO) in order to generate the anode of an organic solar cell (OSC). Potentiodynamic and potentiostatic electropolymerization techniques were used to make the conducting polymer deposits (E-PEDOT), which were obtained as a thin film onto the ITO surface. It was possible to control the thickness of the electrodeposited films in the range of 15 to 200nm measured by AFM. With the thinner films (until 100nm), it was observed that its absorbance at 700nm was linearly dependent with their thickness and it was possible to obtain an equation that was used to measure the films thickness of future experiments. The E-PEDOT films were successfully used for constructing OSC's and the efficiency values found were equivalent or slightly superior to those found with the classical PEDOT:PSS anode

Indacenodithienothiophene-Based Ternary Organic Solar Cells

One of the key aspects to achieve high efficiency in ternary bulk-hetorojunction solar cells is the physical and chemical compatibility between the donor materials. Here, we report the synthesis of a novel conjugated polymer (P1) containing alternating pyridyl[2,1,3]thiadiazole between two different donor fragments, dithienosilole and indacenodithienothiophene (IDTT), used as a sensitizer in a host system of indacenodithieno[3,2-b]thiophene,2,3-bis(3-(octyloxy)phenyl)quinoxaline (PIDTTQ) and [6,6]-phenyl C70 butyric acid methyl ester (PC71BM). We found that the use of the same IDTT unit in the host and guest materials does not lead to significant changes in the morphology of the ternary blend compared to the host binary. With the complementary use of optoelectronic characterizations, we found that the ternary cells suffer from a lower mobility-lifetime (μτ) product, adversely impacting the fill factor. However, the significant light harvesting in the near infrared region improvement, compensating the transport losses, results in an overall power conversion efficiency enhancement of ~7% for ternary blends as compared to the PIDTTQ:PC71BM devices

Thin Functional Polymer Films by Electropolymerization

Intrinsically conducting polymers (ICPs) have been widely utilized in organic electronics, actuators, electrochromic devices, and sensors. Many potential applications demand the formation of thin polymer films, which can be generated by electrochemical polymerization. Electrochemical methods are quite powerful and versatile and can be utilized for investigation of ICPs, both for educational purposes and materials chemistry research. In this study, we show that potentiodynamic and potentiostatic techniques can be utilized for generating and characterizing thin polymer films under the context of educational chemistry research and state-of-the-art polymer research. First, two well-known bifunctional monomers (with only two linking sites)—aniline and bithiophene—and their respective ICPs—polyaniline (PANI) and polybithiophene (PBTh)—were electrochemically generated and characterized. Tests with simple electrochromic devices based on PANI and PBTh were carried out at different doping levels, where changes in the UV-VIS absorption spectra and color were ascribed to changes in the polymer structures. These experiments may attract students’ interest in the electrochemical polymerization of ICPs as doping/dedoping processes can be easily understood from observable color changes to the naked eye, as shown for the two polymers. Second, two new carbazole-based multifunctional monomers (with three or more linking sites)—tris(4-(carbazol-9-yl)phenyl)silanol (TPTCzSiOH) and tris(3,5-di(carbazol-9-yl)phenyl)silanol (TPHxCzSiOH)—were synthesized to produce thin films of cross-linked polymer networks by electropolymerization. These thin polymer films were characterized by electrochemical quartz crystal microbalance (EQCM) experiments and nitrogen sorption, and the results showed a microporous nature with high specific surface areas up to 930 m2g−1. PTPHxCzSiOH-modified glassy carbon electrodes showed an enhanced electrochemical response to nitrobenzene as prototypical nitroaromatic compound compared to unmodified glassy carbon electrodes

Electrogenerated Thin Films of Microporous Polymer Networks with Remarkably Increased Electrochemical Response to Nitroaromatic Analytes

Thin films of microporous polymer networks (MPNs) have been generated by electrochemical polymerization of a series of multifunctional carbazole-based monomers. The microporous films show high Brunauer–Emmett–Teller (BET) surface areas up to 1300 m² g^–1 as directly measured by krypton sorption experiments. A correlation between the number of polymerizable carbazole units of the monomer and the resulting surface area is observed. Electrochemical sensing experiments with 1,3,5-trinitrobenzene as prototypical nitroaromatic analyte demonstrate an up to 180 times increased current response of MPN-modified glassy carbon electrodes in relation to the nonmodified electrode. The phenomenon probably involves intermolecular interactions between the electron-poor nitroaromatic analytes and the electron-rich, high surface area microporous deposits, with the electrochemical reduction at the MPN-modified electrodes being an adsorption-controlled process for low scan rates. We expect a high application potential of such MPN-modified electrodes for boosting the sensitivity of electrochemical sensor devices

Microbiologically Induced Carbonate Precipitation in the Restoration and Conservation of Cultural Heritage Materials

Microbiologically induced carbonate precipitation (MICP) is a well-known biogeochemical process that allows the formation of calcium carbonate deposits in the extracellular environment. The high concentration of carbonate and calcium ions on the bacterial surface, which serves as nucleation sites, promotes the calcium carbonate precipitation filling and binding deteriorated materials. Historic buildings and artwork, especially those present in open sites, are susceptible to enhanced weathering resulting from environmental agents, interaction with physical-chemical pollutants, and living organisms, among others. In this work, some published variations of a novel and ecological surface treatment of heritage structures based on MICP are presented and compared. This method has shown to be successful as a restoration, consolidation, and conservation tool for improvement of mechanical properties and prevention of unwanted gas and fluid migration from historical materials. The treatment has revealed best results on porous media matrixes; nevertheless, it can also be applied on soil, marble, concrete, clay, rocks, and limestone. MICP is proposed as a potentially safe and powerful procedure for efficient conservation of worldwide heritage structures

Silicon- or Carbon-Cored Multifunctional Carbazolyl Monomers for the Electrochemical Generation of Microporous Polymer Films

A series of four tetra- or octacarbazolyl-substituted, tetraphenylmethane/-silane monomers have been oxidatively coupled into microporous polymer networks (MPNs). Chemical polymerization with iron­(III) chloride gives bulk MPNs with BET surface areas (<i>S</i>_BET) of up to 1331 m² g^–1 (for the octacarbazolyl-substituted tetraphenyl­methane monomer). Slightly increased <i>S</i>_BET values result for the materials made from the octacarbazolyl monomers if compared to the tetracarbazolyl analogues, while the exchange of the central carbon by a silicon atom leads to decreased surface areas. The latter phenomenon might be related to electronic interactions of aromatic substituents through the silicon centers. This may cause a reduced reactivity of the carbazoles after the initial oxidative couplings and finally a reduced cross-linking density of the resulting MPNs. Moreover, electrochemical oxidative coupling enables the formation of thin polymer films on the working electrode. These films also show high <i>S</i>_BET values that are only slightly reduced if compared to the corresponding bulk MPNs. Electrochemical quartz microbalance measurements allow for an in-situ characterization of the electrochemical MPN generation. Finally, the electrochemical reduction of a series of nitroaromatic compounds (NACs) on MPN-modified glassy carbon electrodes is studied and applied for high sensitivity NACs detection up to the ppb range

Thiophene-Based Microporous Polymer Networks via Chemical or Electrochemical Oxidative Coupling

Four thiophene-based monomers have been synthesized by Stille- or Suzuki-type couplings followed by chemical or electrochemical polymerization into microporous polymer networks (MPNs) with high BET surface areas (<i>S</i>_BET). Similar <i>S</i>_BET values of up to 2020 and 2135 m² g^–1 have been determined for tetraphenyl­methane-cored bulk MPN powders and thin films, respectively. Electrochemical polymerization in boron trifluoride diethyl etherate (BFEE)/dichloromethane (DCM) mixtures allows for the generation of MPN films with optimized porosity. Moreover, an interesting effect of boron trifluoride on the connectivity of the monomeric units during electropolymerization is observed for 3-thienyl-based monomers. Finally, the electrochemical reduction of 1,3,5-trinitro­benzene at MPN-modified glassy carbon (GC) electrodes shows increased cathodic responses compared to nonmodified GC electrodes due to interaction between electron-deficient nitroaromatic analyte and electron-rich MPN film. The influence of the specific surface area of MPNs on the electrochemical response is also studied for this class of materials

Electrochemical Sensors Based on Conducting Polymers for the Aqueous Detection of Biologically Relevant Molecules

Electrochemical sensors appear as low-cost, rapid, easy to use, and in situ devices for determination of diverse analytes in a liquid solution. In that context, conducting polymers are much-explored sensor building materials because of their semiconductivity, structural versatility, multiple synthetic pathways, and stability in environmental conditions. In this state-of-the-art review, synthetic processes, morphological characterization, and nanostructure formation are analyzed for relevant literature about electrochemical sensors based on conducting polymers for the determination of molecules that (i) have a fundamental role in the human body function regulation, and (ii) are considered as water emergent pollutants. Special focus is put on the different types of micro- and nanostructures generated for the polymer itself or the combination with different materials in a composite, and how the rough morphology of the conducting polymers based electrochemical sensors affect their limit of detection. Polypyrroles, polyanilines, and polythiophenes appear as the most recurrent conducting polymers for the construction of electrochemical sensors. These conducting polymers are usually built starting from bifunctional precursor monomers resulting in linear and branched polymer structures; however, opportunities for sensitivity enhancement in electrochemical sensors have been recently reported by using conjugated microporous polymers synthesized from multifunctional monomers

Recent Advances in Hole-Transporting Layers for Organic Solar Cells

Global energy demand is increasing; thus, emerging renewable energy sources, such as organic solar cells (OSCs), are fundamental to mitigate the negative effects of fuel consumption. Within OSC&rsquo;s advancements, the development of efficient and stable interface materials is essential to achieve high performance, long-term stability, low costs, and broader applicability. Inorganic and nanocarbon-based materials show a suitable work function, tunable optical/electronic properties, stability to the presence of moisture, and facile solution processing, while organic conducting polymers and small molecules have some advantages such as fast and low-cost production, solution process, low energy payback time, light weight, and less adverse environmental impact, making them attractive as hole transporting layers (HTLs) for OSCs. This review looked at the recent progress in metal oxides, metal sulfides, nanocarbon materials, conducting polymers, and small organic molecules as HTLs in OSCs over the past five years. The endeavors in research and technology have optimized the preparation and deposition methods of HTLs. Strategies of doping, composite/hybrid formation, and modifications have also tuned the optical/electrical properties of these materials as HTLs to obtain efficient and stable OSCs. We highlighted the impact of structure, composition, and processing conditions of inorganic and organic materials as HTLs in conventional and inverted OSCs

Magnetic Separation and Enrichment of Fe–Ti Oxides from Iron Titaniferous Beach Sands: Process Design Applied to Coastal Ecuador

Iron titaniferous sands, also called black sands, are a source of various magnetic minerals, such as iron and titanium (Fe–Ti) oxides, with countless scientific and industrial applications. Ecuador is deemed a geo-diverse country that contains deposits of black sands in the Andean and coastal regions; therefore, the industrialization of these magnetic sands might be of high interest. This study presents a preliminary industrial design for the magnetic separation process of Fe–Ti oxides from iron titaniferous Ecuadorian beach sands. Four stages are considered for the process, involving collecting, drying, screening, and magnetic separation. This proposal returns the large particles (>150 μm) and the non-magnetic fraction to the original place, generating a minimum environmental impact with the support of natural marine and coastal processes. The process design criteria are based on engineering guidelines, sampling, and characterization of eleven black sand samples. Using conventional techniques, the water content, granulometric distribution, particle size, and semi-quantitative Fe–Ti oxide concentration were determined for the different sand samples. It is estimated that Fe–Ti oxide production may reach 5.835 metric tons per day (5.835 mtpd) with a magnetic content of 97.50%, starting from 100 mtpd of black sands. Based on an economic analysis (Class V), a net profit of USD 835,875.63 is expected during the first year of production. Thus, the magnetic separation and enrichment of Fe–Ti oxides from iron titaniferous coastal sands exploitation should allow the commercial valorization of these resources in an eco-friendly way, i.e., with economic benefits and minimization of environmental impact in the source area