1,409 research outputs found
Protestation des apostolischen Nuntius in der Schweiz gegen das Dekret des katholischen Grossen Raths des Kantons St. Gallen vom 28. Okt. 1833, die Bisthumsangelegenheiten betreffend
No full text[Filippo de Angelis]Genaue Datierung: "Luzern, den 22. November 1833. Der apostolische Nuntius bei der schweizerischen Eidgenossenschaft, Ph., Erzbischof von Carthago.
Design of Ru(II) sensitizers endowed by three anchoring units for adsorption mode and light harvesting optimization
No full textWe report the design, synthesis and computational investigation of a class of Ru(II)-dyes based on mixed bipyridine ligands for use in dye-sensitized solar cells. These dyes are designed to preserve the optimal anchoring mode of the prototypical N719 sensitizer by three carboxylic groups, yet allowing for tunable optimization of their electronic and optical properties by selective substitution at one of the 4-4′ positions of a single bipyridine ligand with π-excessive heteroaromatic groups. We used Density Functional Theory/Time Dependent Density Functional Theory calculations to analyze the electronic structure and optical properties of the dye and to investigate the dye adsorption mode on a TiO2 nanoparticle model. Our results show that we are effectively able to introduce three carboxylic anchoring units into the dye and achieve at the same time an enhanced dye light harvesting, demonstrating the design concept. As a drawback of this type of dyes, the synthesis leads to a mixture of dye isomers, which are rather tedious to separate
Alignment of energy levels in dye/semiconductor interfaces by GW calculations: Effects due to coadsorption of solvent molecules
No full textThe performance of dye-sensitized solar cells is tightly linked to the relative energy level alignment of its constituents. In this paper the electronic properties of a model of dye-sensitized solar cell are studied by accurate first-principle calculations taking into account many-body effects beyond density-functional theory. The cell model includes one layer of co-adsorbed solvent (water or acetonitrile) molecules. Solvent molecules induce an upwards energy shift in the TiO2bands; such a shift is larger in the case of acetonitrile. The accurate determination of the energy levels allows the theoretical estimation of the maximum attainable open circuit voltage (Voc).This document is the Accepted Manuscript version of a Published Work that appeared in final form in PHYSICAL REVIEW B, copyright ©2014 American Physical Society after peer review and technical editing by the publisher.
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.90.15541
Selective TDDFT with automatic removal of ghost transitions: application to a perylene-dye-sensitized solar cell model
No full textWe present an application of a selective time-dependent density-functional theory (TDDFT)
scheme to a model for a dye-sensitized solar cell (DSSC) with a perylene sensitizer dye on a
TiO2 nanoparticle model. In an earlier study on this system [De Angelis, Chem. Phys. Lett.,
2010, 493, 323], it was reported that a large number of conduction-band excitations severely
complicate the identification of the bright p - p* excitations of the perylene dye. Here, we show
that this problem can be overcome by applying a selective TDDFT solver based on a guess for
the relevant orbital transition in combination with a suitable root-homing scheme. In order to
enhance the efficiency of this algorithm we implement an automatic removal scheme for
artificially low-lying long-range charge-transfer transitions from the TDDFT eigenvalue problem.
A large number of such transitions appear in explicitly solvated systems in the form of
inter-solvent or solvent–solute transitions. We study the characteristics of this removal scheme for
a small water cluster and then apply it in a TDDFT calculation to a perylene–TiO2 nanoparticle
model system and to perylene explicitly solvated in methanol. It is demonstrated that this scheme
leads to a large reduction in the computational cost with essentially no loss in accuracy. Large
differences in the effect of adsorption on the excited states of perylene dyes with two different
anchor groups found in earlier work are confirmed.[Original citation, including DOI link to article on rsc.org] – Reproduced by permission of The Royal Society of Chemistr
Perovskite Solar Cells on Their Way to the Market
No full textI recently attended the third Perovskite Solar Cells and
Optoelectronics (PSCO) conference, which was held
September 18−20, 2017 in Oxford (U.K.). Along with
Henry Snaith, Md. K. Nazeeruddin, and Annamaria Petrozza, I
served as one of the co-Organizers of this meeting.
The conference was an occasion to interact with nearly 400
attendees and capture the latest advances from international
researchers (∼100 oral and ∼170 poster presentations) in the
metal-halide perovskites field, including the Perovskite Death
Starlet, see Figure 1. This PSCO conference became a
cornerstone, at least in my perception, of how far and how
quickly the perovskite field has advanced toward the launch of a
possible industrial product. Although most of the presentations
were devoted to basic science, including elaborate theoretical
chemistry, materials science, and solid-state physics concepts,
discussions and presentations related to practical applications
were prominent. This evolution of the theme, I believe, is a
kind of unique aspect of perovskites, which have raised
tremendous interest both from fundamental academic and
industrial perspectives.
While basic science studies continue to reveal the factors
behind the intriguing properties of perovskite materials, several
companies worldwide are progressing toward the launch of
perovskite solar cell panels in the market. Today, the debate
centers on whether perovskites will make their way through the
photovoltaic market as standalone devices, or whether tandem
devices with silicon (or other established technologies) will be
the first perovskite products to be launched.
To give an account of the latest industrial developments in
perovskite solar cells, I have gathered a few quotes from the
representatives of three industrial participants at PSCO:
“The recent, very successful PSCO 2017 conference supports
the view of Oxford PV that perovskite-based PV has made
substantial progress towards industrialization. As The Perovskite Company, we are working to demonstrate a full silicon−
perovskite solar cell at our facility in Brandeburg an der Havel, a
key step on the path to commercialize this important
technology.” Chris Case, Chief Technology Officer, Oxford
Photovoltaic
The Impact of Machine Learning in Energy Materials Research: The Case of Halide Perovskites
No full textPublishing Hybrid/Organic Photovoltaics Papers in ACS Energy Letters
No full textWith the swift surge of organohalide metal perovskites
as a major player in the arena of emerging
photovoltaic technologies, the field of traditional
Hybrid/Organic Photovoltaics (HOPV) has been profoundly
modified. By traditional HOPV, here we mean dye-sensitized
solar cells (DSCs), bulk heterojunction or small-molecule
organic solar cells (OSCs), and quantum dot solar cells
(QSCs). These technologies dominated publications in basic
and applied science journals up to 2012, when the perovskite
storm started with the first reports of high-efficiency solid-state
perovskite solar cells.1,2 Despite being initially based on a
typical DSC architecture,3 perovskite solar cells have outperformed their DSC ancestor in about 2 years from their
inception, demonstrating a high efficiency (>22%) in a variety
of solid-state device architectures, ranging all the way from a
planar to a mesoscopic heterojunction. Since 2012, traditional
HOPV technologies have been somehow lying in the shadow of
the perovskite giant, mainly due to the efficiency gap between
traditional HOPV (topping after 2 decades of research at 11−
14%) and perovskite solar cells
Ab Initio Modeling of Solar Cell Dye Sensitizers: The Hunt for Red Photons Continues
No full textDespite the swift surge of lead halide perovskites, research in dye-sensitized solar cells (DSCs) has continued over the last few years, with a steady increase in record device efficiencies. A major requisite of an efficient solar cell sensitizer is that of showing an extended UV/Vis absorption spectrum closely matching that of solar radiation. This has given rise to what we call here the hunt for red photons, and ab initio computational modeling plays a major role in designing and screening new dyes with tailored characteristics. In this microreview, we highlight recent developments in modeling transition metal polypyridyl dyes by means of advanced ab initio simulations, including solvation and relativistic effects. We illustrate the molecular design rules that have led to the best performing ruthenium and osmium dyes to date, showing the information which can be extracted from ab initio simulations and how to exploit such information for engineering novel dye candidates
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