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A one-step synthesis of porphyrin-silver acetylide clusters from tetra alkyne-substituted porphyrin is described. The solid-state properties of three 2D-like compounds were fully characterised using XPS and XRD while their catalytic properties under CO2 electroreduction reaction conditions were assessed and their faradaic efficiency quantified.
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A bioinspired polymeric membrane capable of shifting the selectivity of a copper oxide electrocatalyst in the CO2 reduction reaction is described. The membrane is deposited on top of copper oxide thin films from wet deposition techniques under controlled conditions of humidity and self-assembles into an arranged network of micrometer-sized pores throughout the polymer cross-section. The membrane was composed of a block copolymer with a precisely controlled ratio of poly-4-vinylpyridine and poly(methyl methacrylate) blocks (PMMA-b-P4VP). The intrinsic hydrophobicity, together with the porous nature of the membrane's surface, induces a Cassie-Baxter wetting transition above neutral pH, resulting in water repulsion from the catalyst surface. As a consequence, the catalyst's surface is shielded from surrounding water molecules under CO2 electroreduction reaction conditions, and CO2 molecules are preferentially located in the vicinity of the catalytically active area. The CO2 reduction reaction is therefore kinetically favored over the hydrogen evolution reaction (HER).
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Coupling polymer and ionic liquids with electrodes for catalysis is a promising tool for optimization of electrocatalytic CO2 reduction reaction (CO2RR). Here, block copolymer ionic liquids BCPILs were synthesized via controlled radical polymerization and nucleophilic post-substitution to introduce imidazole moieties. We show that, thanks to these PIL functionalities, the BCPIL/Re@HPC/GDL electrode can keep the selectivity toward CO when a higher amount of water is present in the electrolyte than the raw Re@HPC/GDL system. Our results help to understand the development of solid-state ionic liquids for enhanced CO2RR in water-based electrolyte.
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Two new perylenediimides (PDIs) have been developed for use as electron acceptors in solution-processed bulk heterojunction solar cells. The compounds were designed to exhibit maximal solubility in organic solvents, and reduced aggregation in the solid state. In order to achieve this, diphenylphenoxy groups were used to functionalize a monomeric PDI core, and two PDI dimers were bridged with either one or two thiophene units. In photovoltaic devices prepared using PDI dimers and a monomer in conjunction with PTB7, it was found that the formation of crystalline domains in either the acceptor or donor was completely suppressed. Atomic force microscopy, X-ray diffraction, charge carrier mobility measurements and recombination kinetics studies all suggest that the lack of crystallinity in the active layer induces a significant drop in electron mobility. Significant surface recombination losses associated with a lack of segregation in the material were also identified as a significant loss mechanism. Finally, the monomeric PDI was found to have sub-optimum LUMO energy matching the cathode contact, thus limiting charge carrier extraction. Despite these setbacks, all PDIs produced high open circuit voltages, reaching almost 1 V in one particular case.
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In this paper, we demonstrate that zinc oxide (ZnO) layers deposited by inkjet printing (IJP) can be successfully applied to the low-temperature fabrication of efficient inverted polymer solar cells (i-PSCs). The effects of ZnO layers deposited by IJP as electron transport layer (ETL) on the performance of i-PSCs based on PTB7-Th:PC70BM active layers are investigated. The morphology of the ZnO-IJP layers was analysed by AFM, and compared to that of ZnO layers deposited by different techniques. The study shows that the morphology of the ZnO underlayer has a dramatic effect on the band structure and non-geminate recombination kinetics of the active layer deposited on top of it. Charge carrier and transient photovoltage measurements show that non-geminate recombination is governed by deep trap states in devices made from ZnO-IJP while trapping is less significant for other types of ZnO. The power conversion efficiency of the devices made from ZnO-IJP is mostly limited by their slightly lower J SC, resulting from non-optimum photon conversion efficiency in the visible part of the solar spectrum. Despite these minor limitations their J-V characteristics compare very favourably with that of devices made from ZnO layer deposited using different techniques.
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A detailed account of the limiting factors of solvent-annealed bulk-heterojunction small-molecule organic solar cells is given. This account is based on the extensive characterisation of solar cell devices made from a library of five diketopyrolopyrole (DPP) donor dyes. Their chemical structure is designed in such a way as to provide insights into the energetics of solar cell active layer micro-structure formation. Numerous chemical and physical properties of the active layers are assessed and inter-related such as light absorption, molecular packing in the solid state, crystal-forming properties in thin films, charge carrier mobility and charge carrier recombination kinetics. A myriad of characterisation techniques are used such as UV/Vis absorption spectroscopy, photoluminescence spectroscopy, XRD, AFM and photo-induced transient measurements, which provide information on the optical properties of the active layers, morphology and recombination kinetics. Consequently, a mechanism for the solvent-vapour-annealing-assisted formation of crystalline domains of donor molecules in the active layer is proposed, and the micro-structural features are related to the J-V characteristics of the devices. According to this model, the crystalline phase in which the donor crystallise in the active layer is the key determinant to direct the formation of the micro-structure.
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Suministros de Energía Eléctrica , Pirroles/química , Energía Solar , Solventes/químicaRESUMEN
We report the synthesis of a solution-processable, dodecyloxyphenyl-substituted azafullerene monoadduct (DPC59N) and its application as electron acceptor in bulk heterojunction organic solar cells (BHJ-OSCs). Due to its relatively strong absorption of visible light, DPC59N outperforms PC60BM in respect to short circuit current (JSC) and external quantum efficiency (EQE) in blends with donor P3HT.
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Compuestos Aza/química , Suministros de Energía Eléctrica , Fulerenos/química , Energía SolarRESUMEN
The effect of alkyl chains in substituted diphenylmethano[70]fullerenes (C70-DPM) on the device characteristics of DPP(TBFu)2 small molecule-based bulk heterojunction (BHJ) organic solar cell devices is investigated. By measuring charge carrier mobilities as well as the morphology and crystallinity of each device we have been able to understand and explain the differences found between solar cells made with the different C70-DPM fullerenes despite the general lack of simple relationships between the molecular structure, orbital level positioning and power conversion efficiency. Our study then concludes with some general rules for the future design of acceptors for DPP(TBFu)2 containing photoactive layers in the search for efficient organic solar cells.
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A tandem solar cell device whose sub-cells are fabricated exclusively from small molecules (SMs) through both solution-processed and vacuum-processed deposition techniques is described. The front sub-cell's active layer consists of a bulk heterojunction (BHJ) DPP(TBFu)2:PC70BM device while the back cell has a typical bilayer structure employing a 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (SQ) donor and a C60 acceptor.
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A [2]rotaxane, in which the peptidic axle is protected from degradation by the macrocyclic sheath and terminated with a novel glycosidase-cleavable stopper, is rendered water-soluble by derivatisation with tetra(ethylene glycol) (TetEG) or glucosylated tetra(ethylene glycol) (Glc-TetEG) chains using the CuAAC 'click' reaction. The Glc-TetEG-derivatised rotaxane propeptide is >50 000 times more soluble in aqueous media than the parent rotaxane. Activation of the water-soluble rotaxane propeptide with a ß-galactosidase efficiently releases the parent peptide.
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Péptidos/química , Rotaxanos/química , Escherichia coli/enzimología , Glicol de Etileno/química , Espectroscopía de Resonancia Magnética , Péptidos/metabolismo , Rotaxanos/metabolismo , Solubilidad , beta-Galactosidasa/metabolismoRESUMEN
In the Dye Sensitized Solar Cell (DSSC) the dye sensitizer carries out the light harvesting function and is therefore crucial in determining overall cell efficiency. In addition, the dye sensitizer can influence many of the key electron transfer processes occurring at the TiO(2)/dye/electrolyte interface which also determine efficiency. Dye structure can influence and drive forward electron injection into the conduction band of the TiO(2). Conversely, dye structure can help retard loss electron transfer processes such as charge recombination of injected electrons in the TiO(2) with dye cations and also recombination of these electrons with the electrolyte. Therefore tuning dye sensitizer light absorbing properties and control of the aforementioned electron transfer processes through structural design of the dye sensitizer is an important avenue through which optimization of DSSC efficiency should be pursued. In this critical review the latest work focusing on the design of dyes for efficient DSSCs is revised (111 references).
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A convenient method for the stereoselective synthesis of cyclic beta-amino esters from an iodo alphabeta-unsaturated ester and alpha-methylbenzylamine is described. Subsequent enolate generation and alkylation proceeds with complete stereocontrol, with the two stereogenic centres working together. In this way, a functionalised piperidine suitable for alkaloid natural product synthesis was prepared. The usefulness of the methodology is exemplified with the concise synthesis of a (-)-sparteine surrogate.
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Ésteres/química , Ésteres/síntesis química , Esparteína/química , Esparteína/síntesis química , Alquilación , Cristalografía por Rayos X , Ciclización , Modelos Químicos , EstereoisomerismoRESUMEN
A synthetic approach to rotaxane architectures is described in which metal atoms catalyze covalent bond formation while simultaneously acting as the template for the assembly of the mechanically interlocked structure. This "active-metal" template strategy is exemplified using the Huisgen-Meldal-Fokin Cu(I)-catalyzed 1,3-cycloaddition of azides with terminal alkynes (the CuAAC "click" reaction). Coordination of Cu(I) to an endotopic pyridine-containing macrocycle allows the alkyne and azide to bind to metal atoms in such a way that the metal-mediated bond-forming reaction takes place through the cavity of the macrocycle--or macrocycles--forming a rotaxane. A variety of mono- and bidentate macrocyclic ligands are demonstrated to form [2]rotaxanes in this way, and by adding pyridine, the metal can turn over during the reaction, giving a catalytic active-metal template assembly process. Both the stoichiometric and catalytic versions of the reaction were also used to synthesize more complex two-station molecular shuttles. The dynamics of the translocation of the macrocycle by ligand exchange in these two-station shuttles could be controlled by coordination to different metal ions (rapid shuttling is observed with Cu(I), slow shuttling with Pd(II)). Under active-metal template reaction conditions that feature a high macrocycle:copper ratio, [3]rotaxanes (two macrocycles on a thread containing a single triazole ring) are also produced during the reaction. The latter observation shows that under these conditions the mechanism of the Cu(I)-catalyzed terminal alkyne-azide cycloaddition involves a reactive intermediate that features at least two metal ions.