1,721,031 research outputs found
Multi adducts of diphenylmethanofullerenes as electron acceptors for polymer solar cells: A quantum chemical study
No full textIn the present study, quantum chemical methods were applied to investigate the energy levels of the frontier orbital of mono and multi adducts of diphenylmethanofullerenes (DPMs). Recently these molecules have been used as electron acceptors in polymer solar cells showing interesting properties compared to the widely used [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM). The geometries of all the investigated compounds were optimized with the density functional theory at the B3LYP/3-21G level of calculation. We studied the effect of electron-donating (methoxy and methyl thioether) and electron-withdrawing (fluorine) substituents (placed on the diphenylmethano addend in ortho, meta and para position of the phenyl rings), on the lowest unoccupied molecular orbital (LUMO) level of DPM. Afterward, we analysed all the possible isomers arising from bis and tris additions to fullerene cage. The LUMO level is significantly raised compared to the mono adduct but different isomers have different LUMO levels. Since the open circuit voltage (V oc) for polymer solar cells with ohmic contacts is proportional to the difference between the highest occupied molecular orbital (HOMO) of the donor polymer and the LUMO of the acceptor (fullerene), these bisadducts have the potential to increase the Voc of the corresponding devices. Copyright © 2013 American Scientific Publishers All rights reserved
Confinement of Semiconductor ZnO Nanoparticles in Block Copolymer Nanostructure
No full textThe morphology and the electrical properties of hybrid nanocomposites characterized by the dispersion of ZnO nanoparticles (NPs), a n-type semiconductor, within an organic nanostructured matrix of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymer are presented. A selective inclusion of NPs only into the lamellar PS nanodomains of the block copolymer matrix has been achieved by synthetizing ZnO NPs coated with n-hexadecylamine (HDA) and tert-butylphosphonic acid (TBPA) molecules and subsequent thermal annealing of the nanocomposites ZnO NPs/PS-b-PMMA. Thermal treatments have allowed obtaining in one step the vertical orientation of the lamellar BCP nanodomains and the migration of the NPs to the PS domains, resulting in the formation of nanocomposites characterized by a precise control of the position of n-semiconductor ZnO NPs. Current-voltage measurements on the nanocomposites have indicated the presence of continuous path of charge carriers in the BCP films when the ZnO NPs content is above a threshold concentration. The experimental results have allowed the setup and validation of a theoretical protocol to study heterogeneous interfaces. In particular, the interaction of ZnO most stable nonpolar surface with prototypical capping agents has been analyzed by using density functional theory (DFT) calculations. © 2017 American Chemical Society
Nanocomposites from block copolymer lamellar nanostructures and selective gold deposition
No full textInnovative hybrid nanocomposites based on a nanostructured block copolymer (BCP) matrix whose lamellar nanodomains are selectively loaded with metal nanoparticles, have been prepared. A symmetric poly(styrene-b- methylmethacrylate) (PS-b-PMMA) amorphous BCP showing a lamellar morphology has been employed. Thin films of PS-b-PMMA were deposited by spin-coating or drop casting on indium thin oxide (ITO) substrate in order to achieve orientation of lamellae with the lamellar surface perpendicular to the substrate. The perpendicular orientation is related to the use of ITO substrate, which shows a neutral surface with non-preferential interactions with the PS and PMMA domains. Hybrid nanocomposites have been then prepared by selective incorporation of gold nanoparticles into the PS lamellar domain by using a simple method based on the selective deposition of thermally evaporated gold nanoparticles. This innovative approach can be very useful for the realization of nanocomposites that could be used as active layer in non-volatile OFET memory devices or very efficient organic solar cells, depending on the appropriate guest molecules. Copyright © 2013 American Scientific Publishers All rights reserved
Selective inclusion of chromophore molecules into poly(styrene-b-methylmethacrylate) block copolymer nanodomains: a study of morphological, optical and electrical properties
No full textInnovative nanocomposites based on a nanostructured block copolymer (BCP) matrix whose lamellar nanodomains are selectively loaded with organic molecules, were prepared. A symmetric poly(styrene-b-methylmethacrylate) (PS-b-PMMA) amorphous BCP showing a lamellar morphology was employed. Thin films of PS-b-PMMA were deposited by spin-coating on indium thin oxide (ITO) substrate in order to achieve orientation of lamellae with the lamellar surface perpendicular to the substrate. Nanocomposites were then prepared by selective incorporation of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) molecules into the PS lamellar domain. The self-assembly of the BCP generated the nanotemplate to selectively control the spatial location of the PCBM molecules, in which the apolar properties of PS block provided the physical stabilization for achieving uniform PCBM distribution. These innovative approaches can be utilized as a tool to realize memory devices. © 2014, Springer Science+Business Media New York
Toward hyperuniform disordered plasmonic nanostructures for reproducible surface-enhanced Raman spectroscopy
No full textWe report on the self-assembling of clusters of gold-nanoparticles (Au-NPs) directed by the phase separation of poly(styrene)-b-poly(methylmethacrylate) (PS-b-PMMA) block-copolymer (BCP) on indium tin oxide coated glass, which induces the onset of vertical lamellar domains. After thermal evaporation of gold on BCP, Au-NPs of 4 nm are selectively included into PS-nanodomains by thermal annealing, and then clustered with large density of hot spots (> 104 μm2) in a random two-dimensional pattern. The resulting nanostructure exhibits near-hyperuniform long-range correlations. The consequent large degree of homogeneity of this isotropic plasmonic pattern gives rise to a highly reproducible Surface-Enhanced Raman Scattering (SERS) enhancement factor over the centimeter scale (std. dev. ∼ 10% over 0.25 cm2). We also discuss the application of a static electric field for modulating the BCP host morphology. The electric field induces an alignment of Au-NP clusters into ordered linear chains, exhibiting a stronger SERS activity, but reduced SERS spatial reproducibility. © 2015 the Owner Societies
Worldwide outdoor round robin study of organic photovoltaic devices and modules
No full textAccurate characterization and reporting of organic photovoltaic (OPV) device performance remains one of the important challenges in the field. The large spread among the efficiencies of devices with the same structure reported by different groups is significantly caused by different procedures and equipment used during testing. The presented article addresses this issue by offering a new method of device testing using "suitcase sample" approach combined with outdoor testing that limits the diversity of the equipment, and a strict measurement protocol. A round robin outdoor characterization of roll-to-roll coated OPV cells and modules conducted among 46 laboratories worldwide is presented, where the samples and the testing equipment were integrated in a compact suitcase that served both as a sample transportation tool and as a holder and test equipment during testing. In addition, an internet based coordination was used via plasticphotovoltaics.org that allowed fast and efficient communication among participants and provided a controlled reporting format for the results that eased the analysis of the data. The reported deviations among the laboratories were limited to 5% when compared to the Si reference device integrated in the suitcase and were up to 8% when calculated using the local irradiance data. Therefore, this method offers a fast, cheap and efficient tool for sample sharing and testing that allows conducting outdoor measurements of OPV devices in a reproducible manner. © 2014 Published by Elsevier B.V
Synthesis of highly regioregular poly[3-(4-alkoxyphenyl)-thiophene]s by oxidative catalysis using copper complexes
No full textA novel, easy, and cost-effective synthetic procedure is reported for the production of very highly regioregular poly[3-(4-alkoxyphenyl)thiophene]s by means of oxidative coupling. Four copper complexes were synthesized and used as catalysts to obtain polymers with higher regioregularity compared to the previous oxidative coupling methodologies reported in the literature and similar to that obtained by McCullough and Rieke methods in the synthesis of poly-3-alkylthiophenes. The regioregularity of the synthesized polymers was investigated by UV-Visible characterization on polymer thin films and 1H NMR analysis. The remarkable potentialities of these polymers have emerged from field-effect transistor mobility measurements operated on devices with bottom-contact configuration and hexamethyldisilazane-treated SiO 2 gate dielectric, showing a well-defined p-type field-effect response and maximum mobility values in air higher than 10-4 cm 2 V-1 s-1. © 2013 Wiley Periodicals, Inc
Olefins Coordinated at a Highly Electrophilic Site - Dicationic Palladium(II) Complexes and their Equilibrium Reactions with Nucleophiles
No full textRound robin performance testing of organic photovoltaic devices
No full textThis study addresses the issue of poor intercomparability of measurements of organic photovoltaic (OPV) devices among different laboratories. We present a round robin performance testing of novel OPV devices among 16 laboratories, organized within the framework of European Research Infrastructure Project (SOPHIA) and European Energy Research Alliance (EERA). Three types of OPVs with different structures, dimensions and encapsulations are studied and compared with reference Si solar cells certified by accredited laboratories. The agreement of the measurements of these among different laboratories is analyzed by focusing on testing procedures, testing equipment and sample designs. A number of deviations and pitfalls are revealed and based on the analyses, a set of recommendations are suggested for improving the agreement among the measurements of such OPV technologies. © 2013 Elsevier Ltd
Interlaboratory indoor ageing of roll-to-roll and spin coated organic photovoltaic devices: Testing the ISOS tests
No full textThe inter-comparability of ageing of organic photovoltaic (OPV) technologies in dark is addressed. Four primary factors that affect the reproducibility of the ageing rate determination and inter-comparison are discussed: production/encapsulation of the samples, current-voltage (IV) characterization, testing conditions for ageing and lifetime determination from a decay curve. Results of inter-laboratory ageing studies of roll-to-roll and spin coated samples with correspondingly flexible plastic packaging and glass stored in dark conditions among 7 laboratories are presented. ISOS test conditions, proposed recently as guiding protocols for testing OPV stability, are applied in the study. The reproducibility of the performance versus the production and encapsulation techniques is firstly studied. The results reveal a significant improvement in the reproducibility when going from manual spin coating to roll-to-roll production. Furthermore, the reproducibility of current-voltage (IV) measurement and preconditioning (light soaking treatments) are addressed. Additionally, the inter-comparison of the degradation rates of the samples aged under three different dark test conditions (ambient, dry/heat, damp heat) reported by different groups are analyzed revealing a reasonable agreement. Finally, a logarithmic diagram for OPV lifetime associated with common time units is proposed that allows conveniently categorizing and intercomparing the stability performance of different samples aged under different test conditions. © 2014 Elsevier Ltd. All rights reserved
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