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Abstract An efficient method based in template wetting is applied for fabrication of ordered Poly(9,9-dioctylfluorene) (PFO) nanopillars with β-phase morphology. In this process, nanoporous alumina obtained by anodization process is used as template. PFO nanostructures are prepared under ambient conditions via infiltration of the polymeric solution into the pores of the alumina with an average pore diameter of 225 nm and a pore depth of 500 nm. The geometric features of the resulting structures are characterized with environmental scanning electron microscopy (ESEM), luminescence fluorimeter (PL) and micro μ-X-ray diffractometer (μ-XRD). The characterization demonstrates the β-phase of the PFO in the nanopillars fabricated. Furthermore, the PFO nanopillars are characterized by Raman spectroscopy to study the polymer conformation. These ordered nanostructures can be used in optoelectronic applications such as polymer light-emitting diodes, sensors and organic solar cells.

The single-crystal X-ray diffraction technique is employed to explain the synthesis and characterization of a new member of the family of dodecameric oxo clusters, [Sn.sub.12][O.sub.8][(OH).sub.4][(OEt).sub.28][(HOEt).sub.4]. Two different types of trimeric subunits are shown to form the structure of the discussed complex.

A tin(IV) oxoalkoxo cluster with unprecedented architecture has been prepared and characterized by single-crystal X-ray diffraction. The cluster obeys the formula Sn12O8(OH)4(OEt)28(HOEt)4 (1) and is based on an elongated centrosymmetric assembly of 12 six-coordinate tin centers, 28 peripheral ethoxy groups (terminal and bridging), 8 oxo bridges (μ2 and μ3), 4 hydroxy bridges (μ2), and 4 ethanol molecules that are all bound to tin atoms and interact strongly, through hydrogen bonds, with an ethoxy group located on a vicinal tin atom. This compound has also been fully characterized in solution by multinuclear 1D and 2D NMR, with all of its 119Sn, 1H, and 13C NMR resonances assigned with respect to the structure. Altogether, the data allowed unambiguous location of the hydroxy groups. Information on the exchange of the ethoxy groups is also presented. [ABSTRACT FROM AUTHOR]

Abstract: We report in this work the preparation and characterization of hybrid materials from a novel tin(IV) alkoxodimer of formula [Sn(OPr i )2(O2CC(CH3)CH2)2]2 (OPr i =(CH3)2CHO) whose structure has been determined by X-ray diffraction and NMR spectroscopy. This molecule has been used as a nanobuilding block in the preparation of new hybrid materials by combining it with several organic monomers, like methyl methacrylate, ethyl acrylate and styrene, at different molar ratios. The obtained polymers have been characterized by several techniques. The results show that the dimer is incorporated in the polymer network by organic bonds that cross-link the polymer chains very efficiently. Consequently, the incorporation of the cluster has improved the thermal properties of the parent polymer allowing their modulation by adjusting the concentration of the cluster. [Copyright &y& Elsevier]

The generation of stable white light emission using lead-free perovskites remains a huge challenge in the development of future display and lighting technologies, due to fast material deterioration and the decrease of the color quality. In this work, we report a combination of diverse types of 2D A 2 SnX 4 (A = bulky cation, X = Br, I) perovskites exhibiting self-trapped exciton (STE) emission and blue luminescent carbon quantum dots (CQDs), with the purpose of generating A 2 SnX 4 /CQD inks with a broadband emission in the visible region and a tunable white light color. By varying the concentration of the 2D perovskite, the white emission of the mixtures is modulated to cool, neutral, and warm tonalities, with a PL quantum yield up to 45%. From the combinations, the PEA 2 SnI 4 /CQD-based ink shows the longest stability, due to suitable surface ligand passivation provided by the capping ligands covering the CQDs, compensating the defect sites in the perovskite. Then, by incorporating the PEA 2 SnI 4 /CQDs inks into an acrylate polymer matrix, the quenching of the PL component from the perovskite was restrained, being stable for >400 h under ambient conditions and at a relative humidity of ∼50%, and allowing the preparation of complex 3D-printed composites with stable white emission tonalities. This contribution offers an application of STE-based Sn-perovskites to facilitate the future fabrication of lead-free white-light optoelectronic devices.

Hole-transporting materials (HTMs) have demonstrated their crucial role in promoting charge extraction, interface recombination, and device stability in perovskite solar cells (PSCs). Herein, we present the synthesis of a novel dopant-free spiro-type fluorine core-based HTM with four ethoxytriisopropylsilane groups ( Syl-SC ) for inverted planar perovskite solar cells (iPSCs). The thickness of the Syl-SC influences the performance of iPSCs. The best-performing iPSC is achieved with a 0.8 mg/mL Syl-SC solution (ca. 15 nm thick) and exhibits a power conversion efficiency (PCE) of 15.77%, with J sc = 20.00 mA/cm 2 , V oc = 1.006 V, and FF = 80.10%. As compared to devices based on PEDOT:PSS, the iPSCs based on Syl-SC exhibit a higher V oc , leading to a higher PCE. Additionally, it has been found that Syl-SC can more effectively suppress charge interfacial recombination in comparison to PEDOT:PSS, which results in an improvement in fill factor. Therefore, Syl-SC , a facilely processed and efficient hole-transporting material, presents a promising cost-effective alternative for inverted perovskite solar cells.

Electro- and photochemical CO 2 reduction (CO 2 R) is the quintessence of modern-day sustainable research. We report our studies on the electro- and photoinduced interfacial charge transfer occurring in a nanocrystalline mesoporous TiO 2 film and two TiO 2 /iron porphyrin hybrid films ( meso -aryl- and β-pyrrole-substituted porphyrins, respectively) under CO 2 R conditions. We used transient absorption spectroscopy (TAS) to demonstrate that, under 355 nm laser excitation and an applied voltage bias (0 to -0.8 V vs Ag/AgCl), the TiO 2 film exhibited a diminution in the transient absorption (at -0.5 V by 35%), as well as a reduction of the lifetime of the photogenerated electrons (at -0.5 V by 50%) when the experiments were conducted under a CO 2 atmosphere changing from inert N 2 . The TiO 2 /iron porphyrin films showed faster charge recombination kinetics, featuring 100-fold faster transient signal decays than that of the TiO 2 film. The electro-, photo-, and photoelectrochemical CO 2 R performance of the TiO 2 and TiO 2 /iron porphyrin films are evaluated within the bias range of -0.5 to -1.8 V vs Ag/AgCl. The bare TiO 2 film produced CO and CH 4 as well as H 2 , depending on the applied voltage bias. In contrast, the TiO 2 /iron porphyrin films showed the exclusive formation of CO (100% selectivity) under identical conditions. During the CO 2 R, a gain in the overpotential values is obtained under light irradiation conditions. This finding was indicative of a direct transfer of the photogenerated electrons from the film to absorbed CO 2 molecules and an observed decrease in the decay of the TAS signals. In the TiO 2 /iron porphyrin films, we identified the interfacial charge recombination processes between the oxidized iron porphyrin and the electrons of the TiO 2 conduction band. These competitive processes are considered to be responsible for the diminution of direct charge transfer between the film and the adsorbed CO 2 molecules, explaining the moderate performances of the hybrid films for the CO 2 R.

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., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Graphene and carbon quantum dots have extraordinary optical and electrical features because of their quantum confinement properties. This makes them attractive materials for applications in photovoltaic devices (PV). Their versatility has led to their being used as light harvesting materials or selective contacts, either for holes or electrons, in silicon quantum dot, polymer or dye-sensitized solar cells. In this review, we summarize the most common uses of both types of semiconducting materials and highlight the significant advances made in recent years due to the influence that synthetic materials have on final performance.

The influence of the chain length and the molecular weight distribution of the electroluminescent polymer on the carrier transport properties and morphology of air stable hybrid light-emitting diodes is reported. It is found that variations between diverse as-received commercial batches play a major role in the performance of the devices, whose maximum luminance can differ up to 2 orders of magnitude. Through complementary optoelectronic, structural, and morphological characterization techniques, we provide insights into the relationship between charge dynamics and the structure of polymeric electroluminescent materials. The carrier dynamics are found to be dominated by both the polymeric chain length and the hole transport, which in turn is dependent on the concentration of trap states. Furthermore, the chain length is seen to affect the morphology of the active layer.

We demonstrate remarkably fast incorporation and high loading of cytochrome c within thin films of periodically ordered nanocrystalline TiO(2) deposited on transparent electrodes. The immobilized cytochrome c is not denaturated and it can be reversibly reduced without mediator over the time scale of a few seconds as evidenced by spectroelectrochemistry.

A series of heteroleptic ruthenium(II) polypyridyl complexes containing phenanthroline ligands have been designed, synthesized, and characterized. The spectroscopic and electrochemical properties of the complexes have been studied in solution and adsorbed onto semiconductor nanocrystalline metal oxide particles. The results show that for two of the ruthenium complexes, bearing electron-donating (-NH2) or electron-withdrawing (-NO2) groups, the presence of the redox-active I(-)/I3(-) electrolyte produces important changes in the interfacial charge transfer processes that limit the device performance. For example, those dyes enhanced the electron recombination reaction between the photoinjected electrons at TiO2 and the oxidized redox electrolyte. In an effort to understand the details of such striking observations, we have monitored the charge transfer reactions taking place at the different interfaces of the devices using time-resolved single photon counting, laser transient spectroscopy, and light-induced photovoltage measurements.