pinecone/core-2020-05-10-deduplication huggingface dataset:
Organic gelators as growth control agents for stable and reproducible hybrid perovskite-based solar cells

Low molecular-weight organic gelators are widely used to influence the solidification of\ud
polymers, with applications ranging from packaging items, food containers to organic\ud
electronic devices, including organic photovoltaics. Here, this concept is extended to hybrid\ud
halide perovskite-based materials. In-situ time-resolved grazing incidence wide angle x-ray\ud
scattering (GIWAXS) measurements performed during spin-coating reveal that organic gelators\ud
beneficially influence the nucleation and growth of the perovskite precursor phase. This can be\ud
exploited for the fabrication of planar n-i-p heterojunction devices with MAPbI3 (MA =\ud
CH3NH3\ud
+) that display a performance that not only is enhanced by ~25% compared to solar\ud
cells where the active layer was produced without the use of a gelator but that also feature a\ud
higher stability to moisture and a reduced hysteresis. Most importantly, the presented approach\ud
is straight-forward and simple, and it provides a general method to render the film-formation\ud
of hybrid perovskites more reliable and robust, analogous to the control that is afforded by these\ud
additives in the processing of commodity ‘plastics’
Interfaces in Perovskite Solar Cells

Rapid improvement in photoconversion efficiency (PCE) of solution processable organometallic hybrid halide based perovskite solar cells (PSCs) have taken the photovoltaic (PV) community with a surprise and has extended their application in other electronic devices such as light emitting diodes, photo detectors and batteries. Together with efforts to push the PCE of PSCs to record values >22% – now at par with that of crystalline silicon solar cells – origin of their PV action and underlying physical processes are also deeply investigated worldwide in diverse device configurations. A typical PSC consists of a perovskite film sandwiched between an electron and a hole selective contact thereby creating ESC/perovskite and perovskite/HSC interfaces, respectively. The selective contacts and their interfaces determine properties of perovskite layer and also control the performance, origin of PV action, open circuit voltage, device stability, and hysteresis in PSCs. Herein, we define ideal charge selective contacts, and provide an overview on how the choice of interfacing materials impacts charge accumulation, transport, transfer/recombination, band-alignment, and electrical stability in PSCs. We then discuss device related considerations such as morphology of the selective contacts (planar or mesoporous), energetics and electrical properties (insulating and conducting), and its chemical properties (organic vs inorganic). Finally, the outlook highlights key challenges and future directions for a commercially viable perovskite based PV technology
Organohalide Perovskites are Fast Ionic Conductors

Fast ionic conductors constitute a family of materials exhibiting high values of the ionic conductivity while their crystal structure remains rather rigid. Perovskite-like compounds are known to be good ionic conductors with applications as solid electrolytes. In hybrid halide perovskites both intrinsic (native) and extrinsic defect migration are regarded to occur. Ion diffusivity analysis is inherently ambiguous in all-solid-state configurations because of the multicomponent environment. Here, a liquid electrolyte in contact to the perovskite material forms a reservoir of Li+ that is forced to intercalate and migrate within the perovskite electrode. This approach decouples different contributions to transport in such a way that ion diffusion kinetics is easily accessible by means of impedance methods. The room-temperature chemical diffusion coefficient of lithium ion within the perovskite lattice exhibits values as high as Dμ ≈ 10−7 cm2 s−1, which implies conductivities within the range of 10−3 Ω−1 cm−1 for highly lithiated electrodes. This confirms the superionic intrinsic property of organohalide perovskites from a direct and unambiguous measurement that does not rely upon simulation tools
Circumventing UV light induced nanomorphology disorder to achieve long lifetime PTB7-Th:PCBM based solar cells

Aquest article pot ser utilitzat per a fins no comercials, d'acord amb  els termes i condicions d’auto-arxiu de Wiley.Large area flexible electronics rely on organic or hybrid materials prone to degradation limiting the device lifetime. For many years, photo-oxidation has been thought to be one of the major degradation pathways. However, intense illumination may lead to a burn-in or a rapid decrease in performance for devices completely isolated from corrosive elements as oxygen or moisture. The experimental studies which are presented in here indicate that a plausible triggering for the burn-in is a spin flip after a UV photon absorption leading to the accumulation of electrostatic potential energy that initiates a rapid destruction of the nanomorpholgy in the fullerene phase of a polymer cell. To circumvent this and achieve highly stable and efficient devices, a robust nanocrystalline ordering is induced in the PCBM phase prior to UV illumination. In that event, PTB7-Th:PC71BM cells are shown to exhibit T80 lifetimes larger than 1.6 years under a continuous UV-filtered 1-sun illumination, equivalent to 7 years for sunlight harvesting at optimal orientation and 10 years for vertical applications.Peer ReviewedPostprint (author's final draft
Graphene-based electron transport layers in perovskite solar cells: a
  step-up for an efficient carrier collection

The electron transport layer (ETL) plays a fundamental role in perovskite
solar cells. Recently, graphene-based ETLs have been proved to be good
candidate for scalable fabrication processes and to achieve higher carrier
injection with respect to most commonly used ETLs. In this work we
experimentally study the effects of different graphene-based ETLs in sensitized
MAPI solar cells. By means of time-integrated and picosecond time-resolved
photoluminescence techniques, the carrier recombination dynamics in MAPI films
embedded in different ETLs is investigated. Using graphene doped mesoporous
TiO2 (G+mTiO2) with the addition of a lithium-neutralized graphene oxide
(GO-Li) interlayer as ETL, we find that the carrier collection efficiency is
increased by about a factor two with respect to standard mTiO2. Taking
advantage of the absorption coefficient dispersion, we probe the MAPI layer
morphology, along the thickness, finding that the MAPI embedded in the ETL
composed by G+mTiO2 plus GO-Li brings to a very good crystalline quality of the
MAPI layer with a trap density about one order of magnitude lower than that
found with the other ETLs. In addition, this ETL freezes MAPI at the tetragonal
phase, regardless of the temperature. Graphene-based ETLs can open the way to
significant improvement of perovskite solar cells.Comment: 7 pages, 5 figures, Supporting Informatio
Tuning of catalytic activity by thermoelectric materials for carbon dioxide hydrogenation

An innovative use of a thermoelectric material (BiCuSeO) as a support and promoter of catalysis for CO2 hydrogenation is reported here. It is proposed that the capability of thermoelectric materials to shift the Fermi level and work function of a catalyst lead to an exponential increase of catalytic activity for catalyst particles deposited on its surface. Experimental results show that the CO2 conversion and CO selectivity are increased significantly by a thermoelectric Seebeck voltage. This suggests that the thermoelectric effect can not only increase the reaction rate but also change chemical equilibrium, which leads to the change of thermodynamic equilibrium for the conversion of CO2 in its hydrogenation reactions. It is also shown that this thermoelectric promotion of catalysis enables BiCuSeO oxide itself to have a high catalytic activity for CO2 hydrogenation. The generic nature of the mechanism suggests the possibility that many catalytic chemical reactions can be tuned in situ to achieve much higher reaction rates, or at lower temperatures, or have better desired selectivity through changing the backside temperature of the thermoelectric support
On the molecular origin of charge separation at the donor-acceptor interface

C.R. thanks the University of Kentucky Vice President for Research and the Department of the Navy, Office of Naval Research (Award No. N00014-16-1-2985) for support. V.C. thanks the Department of the Navy, Office of Naval Research (Awards Nos. N00014-14-1-0580 and N00014-16-1-2520) for support. M.S. and D.D. acknowledge funding by the German Science Foundation through the SPP 1355 “Elementary Processes in Organic Photovoltaics.” The research data supporting this paper can be accessed at https://doi.org/10.17630/a6935caf-f7ed-48b2-b131-68ae72a26629.Fullerene-based acceptors have dominated organic solar cells for almost two decades. It is only within the last few years that alternative acceptors rival their dominance, introducing much more flexibility in the optoelectronic properties of these material blends. However, a fundamental physical understanding of the processes that drive charge separation at organic heterojunctions is still missing but urgently needed to direct further material improvements. Here we use a combined experimental and theoretical approach to understand the intimate mechanisms by which molecular structure contributes to exciton dissociation, charge separation, and charge recombination at the donor-acceptor (D-A) interface. We use model systems comprised of polythiophene-based donor and rylene diimide-based acceptor polymers and perform a detailed density functional theory (DFT) investigation. The results point to the roles that geometric deformations and direct-contact intermolecular polarization play in establishing a driving force (energy gradient) for the optoelectronic processes taking place at the interface. A substantial impact for this driving force is found to stem from polymer deformations at the interface, a finding that can clearly lead to new design approaches in the development of the next generation of conjugated polymers and small molecules.PostprintPeer reviewe
A New Perspective on the Role of A-site Cation in Perovskite Solar Cells

As the race towards higher efficiency for inorganic/organic hybrid perovskite
solar cells (PSCs) is becoming highly competitive, a design scheme to maximize
carrier transport towards higher power efficiency has been urgently demanded.
Here, we unravel a hidden role of A-site cation of PSCs in carrier transport
which has been largely neglected, i.e., tuning the Frohlich electron-phonon
(e-ph) coupling of longitudinal optical (LO) phonon by A-site cations. The key
for steering Frohlich polaron is to control the interaction strength and the
number of proton (or lithium) coordination to halide ion. The coordination to I
alleviates electron-phonon scattering by either decreasing the Born effective
charge or absorbing the LO motion of I. This novel principle discloses lower
electron-phonon coupling by several promising organic cations including
hydroxyl-ammonium cation (NH$_3$OH$^+$) and possibly Li$^+$ solvating
methylamine (Li$^+$NH$_2$CH$_3$) than methyl-ammonium cation. A new perspective
on the role of A-site cation could help in improving power efficiency and
accelerating the application of PSCs.Comment: 7 pages, 4 figure
Switching Off Hysteresis in Perovskite Solar Cells by Fine‐Tuning Energy Levels of Extraction Layers

Lead halide perovskites often suffer from a strong hysteretic behavior on their j–V response in photovoltaic devices that has been correlated with slow ion migration. The electron extraction layer has frequently been pointed to as the main culprit for the observed hysteretic behavior. In this work three hole transport layers are studied with well‐defined highest occupied molecular orbital (HOMO) levels and interestingly the hysteretic behavior is markedly different. Here it is shown that an adequate energy level alignment between the HOMO level of the extraction layer and the valence band of the perovskite, not only suppresses the hysteresis, avoiding charge accumulation at the interfaces, but also degradation of the hole transport layer is reduced. Numerical simulation suggests that formation of an injection barrier at the organic/perovskite heterointerface could be one mechanism causing hysteresis. The suppression of such barriers may require novel design rules for interface materials. Overall, this work highlights that both external contacts need to be carefully optimized in order to obtain hysteresis‐free perovskite devices
Accelerated screening of thermoelectric materials by first-principles
  computations of electron-phonon scattering

Recent discovery of new materials for thermoelectric energy conversion is
enabled by efficient prediction of materials' performance from
first-principles, without empirically fitted parameters. The novel simplified
approach for computing electronic transport properties is described, which
achieves good accuracy and transferability while greatly reducing complexity
and computation cost compared to the existing methods. The first-principles
calculations of the electron-phonon coupling demonstrate that the energy
dependence of the electron relaxation time varies significantly with chemical
composition and carrier concentration, suggesting that it is necessary to go
beyond the commonly used approximations to screen and optimize materials'
composition, carrier concentration, and microstructure. The new method is
verified using high accuracy computations and validated with experimental data
before applying it to screen and discover promising compositions in the space
of half-Heusler alloys. By analyzing data trends the effective electron mass is
identified as the single best general descriptor determining material's
performance. The Lorenz number is computed from first principles and the
universality of the Wiedemann-Franz law in thermoelectrics is discussed.Comment: This is the pre-peer reviewed version of the following article: Adv.
  Energy Mater. 2018, 1800246, which has been published in final form at
  doi:10.1002/aenm.201800246. This article may be used for non-commercial
  purposes in accordance with Wiley Terms and Conditions for Self-Archivin
Self‐assembled hole transporting monolayer for highly efficient perovskite solar cells

The unprecedented emergence of perovskite‐based solar cells (PSCs) has been accompanied by an intensive search of suitable materials for charge‐selective contacts. For the first time a hole‐transporting self‐assembled monolayer (SAM) as the dopant‐free hole‐selective contact in p–i–n PSCs is used and a power conversion efficiency of up to 17.8% with average fill factor close to 80% and undetectable parasitic absorption is demonstrated. SAM formation is achieved by simply immersing the substrate into a solution of a novel molecule V1036 that binds to the indium tin oxide surface due to its phosphonic anchoring group. The SAM and its modifications are further characterized by Fourier‐transform infrared and vibrational sum‐frequency generation spectroscopy. In addition, photoelectron spectroscopy in air is used for measuring the ionization potential of the studied SAMs. This novel approach is also suitable for achieving a conformal coverage of large‐area and/or textured substrates with minimal material consumption and can potentially be extended to serve as a model system for substrate‐based perovskite nucleation and passivation control. Further gains in efficiency can be expected upon SAM optimization by means of molecular and compositional engineering
Ionic Reactivity at Contacts and Aging of Methylammonium Lead Triiodide Perovskite Solar Cells

Hybrid lead halide perovskites have reached very large solar to electricity power conversion efficiencies, in some cases exceeding 20%. The most extensively used perovskite-based solar cell configuration comprises CH3NH3PbI3 (MAPbI3) in combination with electron (TiO2) and hole 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9-spiro-bifluorene (spiro-OMeTAD) selective contacts. The recognition that the solar cell performance is heavily affected by time scale of the measurement and preconditioning procedures has raised many concerns about the stability of the device and reliability for long-time operation. Mechanisms at contacts originate observable current–voltage distortions. Two types of reactivity sources have been identified here: (i) weak Ti–I–Pb bonds that facilitate interfacial accommodation of moving iodine ions. This interaction produces a highly reversible capacitive current originated at the TiO2/MAPbI3 interface, and it does not alter steady-state photovoltaic features. (ii) An irreversible redox peak only observable after positive poling at slow scan rates. It corresponds to the chemical reaction between spiro-OMeTAD+ and migrating I− which progressively reduces the hole transporting material conductivity and deteriorates solar cell performance.Funded by  Ministerio de Economía y Competitividad. Grant Number: MAT2013-47192-C3-1-R and  Generalitat Valenciana. Grant Numbers: Prometeo/2014/020, ACOMP/2015/105
Australian wines in the British wine market: A hedonic price analysis

The market share of New World wines sold in many European countries has increased dramatically over the past decade. More aggressive marketing, together with a more distinct and recognizable labeling scheme, are often regarded as the keys to the marketing success of these new wines. This article employs hedonic price analysis to identify the values that marketers and consumers place on the information carried by the label of Australian wines in the British wine retail market. Although many grape varieties are given a highly distinct valuation by market participants, our results also suggest that consumers consider regions jointly with grape varieties as proxies for brands. This contrasts with the general observation that grape varietal labeling is the distinctive feature of New World wines. Marketing implications are examined by considering the revenue impact of changes in labeling at the retail level
“Use of Scanner Data to Analyze the Table Wine Demand in the Italian Major Retailing Trade”

ABSTRACT\ud
While the utilization of scanner data for food demand analyses has become increasingly popular in\ud
the United States, few food demand studies, and in particular none on table wine, have been conducted\ud
using scanner data in Italy+ This paper presents a first attempt to estimate a demand system\ud
for selected brands of red tetra-packaged, plastic packaged, and bag-in-box table wine using scanner\ud
data providing new and useful insights into the marketing of Italian wine+ Price and expenditure\ud
elasticities of Italian red table wine demand drawn from a linear almost ideal demand system are\ud
provided+ Results suggest a partially loyal market of table wine, showing a tendency to substitution\ud
across brands and a degree of competition among the leading brands+ @EconLit citations: Q110,\ud
Q130#+ © 2006 Wiley Periodicals, Inc
Economies of Scale in the Canadian Food Processing Industry

Cost functions for three Canadian manufacturing agri-food sectors (meat, bakery and dairy) are estimated using provincial data from 1990 to 1999. A translog functional form is used and the concavity property is imposed locally. The Morishima substitution elasticities and returns to scale elasticities are computed for different provinces. Inference is carried out using asymptotic theory as well as bootstrap methods. In particular, the ability of the double bootstrap to provide refinements in inference is investigated. The evidence suggests that there are significant substitution possibilities between the agricultural input and other production factors in the meat and bakery sectors. Scale elasticity parameters indicate that increasing returns to scale are present in small bakery industries. While point estimates suggest that increasing returns to scale exist at the industry level in the meat sector, statistical inference cannot rule the existence of decreasing returns to scale. To account for supply management in the dairy sector, separability between raw milk and the other inputs was introduced. There exists evidence of increasing returns to scale at the industry level in the dairy industries of Alberta and New Brunswick. The scale elasticity for the two largest provinces (Ontario and Quebec) is greater than one, but inference does not reject the null hypothesis of increasing returns to scale.
The Turkish wheat market: spatial price transmission and the impact of transaction costs

Agricultural production is spread all over Turkey and the considerably different climatic and topographical conditions among the provinces lead to highly diversified agricultural production. Therefore, is it reasonable to assume an integrated market all over Turkey? The authors analyze spatial price transmission among 28 Turkish provinces with regard to wheat markets. They apply a bivariate threshold vector error correction model with two symmetric thresholds to account for transaction costs. They find an inner cluster of highly integrated provinces and identify the market size as a driving force of market integration. Furthermore, this study is unique in determining the minimum level of transaction costs. The results suggest that the minimum transaction costs impede full market integration more often on smaller than on larger markets. [EconLit citations: L100; D230; Q110]. \ua9 2010 Wiley Periodicals, Inc
The determinants of electronic traceability adoption: a firm-level analysis of French agribusiness

International audienceThis paper aims to understand what factors influence firms to adopt electronic traceability systems (ETS) and notably the respective effects of the firm's internal characteristics, its vertical relations and its external environment. Traceability systems based on information and communication technologies (ICT) allow firms to collect, track, stock and transfer information on a range of product attributes. This study contributes to further understand traceability adoption by applying ICT adoption models to the case of ETS, and by using an original dataset, the 2002 ICT Survey, representative of all French agribusiness. The results suggest that a firm's degree of complexity (growing size, belonging to a group) and the development of its information system play a significant role in its adoption behavior. Moreover, they show that ETS adoption is more driven by a firm's narrow relations with specialized suppliers and downstream processors than by retailers
Cultural distance and internationalization. The world’s largest food and drink multinationals

The final version of this paper was published by “Agribusiness. An International Journal “, vol 27 (4), 2011.\ud
http://onlinelibrary.wiley.com/doi/10.1002/agr.20283/abstractThis paper analyses the expansion of the world’s largest food and beverage multinational enterprises (hereafter, F&B MNEs) over 1996-2002 using a database that provides detailed information on the location and activities of more than 8,000 affiliates. The research provides abundant empirical support to the view that F&B MNEs operate on a worldwide scale and although their share of foreign to total affiliates is lower than in the average MNE they have a wide country spread. The great physical dispersion of the F&B MNEs’ assets, however, does not necessarily imply expansion to cultural distant areas. World’s leaders in this industry are more likely to expand their operations to countries that display cultural characteristics similar to those of the home-country. We observe differences concerning cultural distance among different companies. Western F&B MNEs seem more culturally rooted than Japanese ones, probably owing to differences in the product-mix and the activities developed by the companies. A comparison of 1996, 2000 and 2002 data shows that F&B MNEs are gradually expanding to increasingly unfamiliar environments. Complementary analysis of 3,507 M&A operations involving the sampled MNEs between 1987 and 2003 confirms these findings.Peer reviewe