1,721,266 research outputs found
Publishing 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
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 textAlignment of the dye's molecular levels with the TiO(2) band edges in dye-sensitized solar cells: a DFT-TDDFT study
No full textWe present a theoretical study of the lineup of the LUMO of Ru(II)-polypyridyl (N3 and N719) molecular dyes with the conduction band edge of a TiO(2) anatase nanoparticle. We use density functional theory (DFT) and the Car-Parrinello scheme for efficient optimization of the dye-nanoparticle systems, followed by hybrid B3LYP functional calculations of the electronic structure and time-dependent DFT (TDDFT) determination of the lowest vertical excitation energies. The electronic structure and TDDFT calculations are performed in water solution, using a continuum model. Various approximate procedures to compute the excited state oxidation potential of dye sensitizers are discussed. Our calculations show that the level alignment for the interacting nanoparticle-sensitizer system is very similar, within about 0.1 eV, to that for the separated TiO(2) and dye. The excellent agreement of our results with available experimental data indicates that the approach of this work could be used as an efficient predictive tool to help the optimization of dye-sensitized solar cells
Unraveling Atomic Contributions to the London Dispersion Energy: Insights into Molecular Recognition and Reactivity
No full textWe present a general framework that enables quantification with atomic resolution of the overall London dispersion energy, which can be readily integrated with currently available energy decomposition schemes. This approach can be used to determine the contribution of individual atoms and functional groups to molecular recognition, conformational preferences, molecular stability, and reactivity. Its efficacy across diverse realms of molecular chemistry and biology is demonstrated with application to molecular balances in solution, asymmetric organocatalytic transformations, and a subcomplex of the F1FO ATP synthase
Full Quantum Mechanical Investigation of the Unimolecular versus Bimolecular Acetylene to Vinylidene Rearrangement in the Prototypetrans-Cl-Rh(Pi-Pr3)2Complex
No full textWe report a full quantum mechanical investigation, based on DFT calculations, on the unimolecular and bimolecular alkyne-vinylidene rearrangements in the prototype [Cl-Rh(Pi-Pr-3)(2)(HC CH)] complex, to solve the discrepancy between theory and recent experimental data and to provide a definitive answer concerning the largely debated molecularity issue of the 1,3-shift in d(8) metal complexes. We calculate the intramolecular pathway to be kinetically favored over the intermolecular one by 15.0 kcal/mol, in agreement with recent crossover experiments. Comparison of our DFT calculations performed on the real systems with reduced models shows that a full quantum mechanical description of the investigated systems is mandatory for a correct description of their reactivity, owing to the relevant role played by the electron-donating phosphine ligands
Time-dependent density functional theory study of the absorption spectrum of [Ru(4,4′-COOH-2,2′-bpy)2(NCS)2] in water solution: Influence of the pH
No full textWe present a combined density functional/time-dependent density functional study of the electronic structure and optical absorption spectrum of the charge-transfer sensitizer cis-[Ru(4,4'-COOH-2,2'-bpY)(2)(NCS)(2)] in water solution. To simulate the effect of different pH values, calculations have been performed for both the title complex and the corresponding tetra-deprotonated species, cis-[Ru(4,4'-COO-2,2'-bPY)(2)(NCS)(2)](4-). The experimentally observed blue-shift of the spectrum at high pH is well reproduced by our theoretical model and appears to be related to destabilization of the bipyridines pi(*) LUMOs as a result of the increased electron density on the deprotonated carboxylic groups. (C) 2004 Elsevier B.V. All rights reserved
Correction to “Computational Investigation of Dye–Iodine Interactions in Organic Dye-Sensitized Solar Cells”
No full textWe present a computational investigation, based on
DFT, MP2, and Car−Parrinello molecular dynamics simulations,
aimed to model the dye−iodine interactions in organic dyesensitized solar cells. We evaluate the binding of I2 and I3
− and Li+
to the various electron-donating sites in organic sensitizers
considering two coumarin dyes differing by the number of
thiophene rings in the bridge (NKX2587 vs NKX2697) and one
carbazole dye (MK3), which have been the subject of a detailed
experimental investigation (J. Am. Chem Soc. 2008, 130, 17874−
17881). We find that oxygen atoms are the preferred binding sites
for I2, while I3
− tends to interact with the π system of the coumarin
donor unit. Our results suggest that the increase of the distance of
the carbonyl oxygen from the titania going from NKX2587 to
NKX2697 could explain the differences in the lifetime values measured for NKX2587-sensitized solar cells compared to those
employing the longer NKX2697 homologues. The shorter lifetime measured for MK3 compared to NKX2687, which have the
same π-spacer and acceptor units, is instead attributed to the twisting of the dye structure in MK3, which possibly forms less
compact dye layers on titania. The effect of the dye structure and Li+ coordination to the dyes on the titania conduction band is
also examined
Structural and electronic properties of organo-halide hybrid perovskites from ab initio molecular dynamics
No full textThe last two years have seen the unprecedentedly rapid emergence of a new class of solar cells, based on hybrid organic–inorganic halide perovskites. The success of this class of materials is due to their outstanding photoelectrochemical properties coupled to their low cost, mainly solution-based, fabrication techniques. Solution processed materials are however often characterized by an inherent flexible structure, which is hardly mapped into a single local minimum energy structure. In this perspective, we report on the interplay between structural and electronic properties of hybrid lead iodide perovskites investigated using ab initio molecular dynamics (AIMD) simulations, which allow the dynamical simulation of disordered systems at finite temperature. We compare the prototypical MAPbI3 (MA = methylammonium) perovskite in its cubic and tetragonal structure with the trigonal phase of FAPbI3 (FA = formamidinium), investigating different starting arrangements of the organic cations. Despite the relatively short time scale amenable to AIMD, typically a few tens of ps, this analysis demonstrates the sizable structural flexibility of this class of materials, showing that the instantaneous structure could significantly differ from the time and thermal averaged structure. We also highlight the importance of the organic–inorganic interactions in determining the fluxional properties of this class of materials. A peculiar spatial localization of the valence and conduction band edges is also found, with a dynamics in the range of 0.1 ps, which is associated with the positional dynamics of the organic cations within the cubo-octahedral perovskite cage. This asymmetry in the spatial localization of the band edges is expected to ease exciton dissociation and assist the initial stages of charge separation, possibly constituting one of the key factors for the impressive photovoltaic performances of hybrid lead-iodide perovskites
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