13 research outputs found
To form a union without having a child. The lengthening of the initial period of life in union before parenthood. A study based on European FFS data
Comunicació presentada a l'European Population Conference: "Migration and Migrants in Europe"(Sessió 53). Organitzat per l'European Association for Population Studies (EAPS); Centre d'Estudis Demogràfics. Barcelona, del 9 al 12 de juliol de 2008.The authors of the Second Demographic Transition scheme single out the postponement of the age at first childbearing as the main effect of the changes in habits of young adults associated with this transition. This postponement is accompanied by an increase in the length of the initial period of life in partnership when the couple has no plan yet to have children. This change is made possible by the use of contraceptive means by people living in partnerships in order to delay first childbearing. This is in sharp contrast with the First Demographic Transition, which was also characterized by the extension of the use of contraceptive means, but only after the birth of children. So contraception was used then to control fertility, when it is used nowadays to extend the period of life when no irreversible decisions, like having a child, have been made yet. In this work, we study various dimensions of this postponement of childbearing by couples. First, we try to quantify the magnitude of the increase in the duration of this initial period, when the couple delays parenthood. Second we have a look at the way this change in fertility behaviours in the first years of union change the duration model that was typical at the end of the First Demographic Transition. Finally, we investigate the possible determinants of the increase of this initial period using data on time spent by women studying and working, and of the transition from cohabitation to marriage. We use data from Fertility and Families Surveys for 17 countries and apply life table techniques and proportional hazard modelling.Un dels principals canvis associats a la Segona Transició Demogràfica és el retard en l'edat de tenir el primer fill, allargant-se el període d'unió sense plans de tenir-los. El retard és possible gràcies a la utilització dels mitjans anticonceptius, fet que contrasta amb la Primera Transició Demogràfica, a on els mitjans anticonceptius s'empraven després del naixement dels fills. En aquest estudi s'analitzen les diverses dimensions d'aquest ajornament. En primer lloc, es quantifica l'augment temporal d'aquest període inicial sense fills; en segon lloc s'analitza la forma en què aquest canvi modifica el model de la Primera Transició Demogràfica; finalment, s'apunten possibles determinants, emprant dades sobre el temps dedicat per les dones a estudiar i a treballar, i de la transició de la cohabitació al matrimoni. La font bàsica d'informació és la Fertility and Families Surveys , per a 17 països.Uno de los principales cambios asociados a la Segunda Transición Demográfica, es el aplazamiento en la edad de tener el primer hijo, ampliándose el período de unión sin planes de tenerlos. La demora es posible gracias a la utilización de los medios anticonceptivos, hecho que contrasta con la Primera Transición Demográfica, donde los medios anticonceptivos se utilizaban después del nacimiento de los hijos. En este estudio se analizan las dimensiones de este aplazamiento. En primer lugar, se cuantifica el aumento temporal de esta etapa inicial sin hijos; en segundo lugar, se analiza la forma en que este cambio modifica el modelo de la Primera Transición Demográfica; finalmente, se apuntan posibles determinantes utilizando datos sobre el tiempo dedicado por las mujeres a estudiar y a trabajar, y de la transición de la cohabitación al matrimonio. La fuente básica de información es la Fertility and Families Surveys, para 17 países
CsI‐Antisolvent Adduct Formation in All‐Inorganic Metal Halide Perovskites
The excellent optoelectronic properties demonstrated by hybrid organic/inorganic metal halide perovskites are all predicated on precisely controlling the exact nucleation and crystallization dynamics that occur during film formation. In general, high‐performance thin films are obtained by a method commonly called solvent engineering (or antisolvent quench) processing. The solvent engineering method removes excess solvent, but importantly leaves behind solvent that forms chemical adducts with the lead‐halide precursor salts. These adduct‐based precursor phases control nucleation and the growth of the polycrystalline domains. There has not yet been a comprehensive study comparing the various antisolvents used in different perovskite compositions containing cesium. In addition, there have been no reports of solvent engineering for high efficiency in all‐inorganic perovskites such as CsPbI3. In this work, inorganic perovskite composition CsPbI3 is specifically targeted and unique adducts formed between CsI and precursor solvents and antisolvents are found that have not been observed for other A‐site cation salts. These CsI adducts control nucleation more so than the PbI2–dimethyl sulfoxide (DMSO) adduct and demonstrate how the A‐site plays a significant role in crystallization. The use of methyl acetate (MeOAc) in this solvent engineering approach dictates crystallization through the formation of a CsI–MeOAc adduct and results in solar cells with a power conversion efficiency of 14.4%.It is found that unique adducts form between CsI and dimethyl sulfoxide (DMSO) and certain antisolvents, such as methyl acetate, during film formation of the all‐inorganic perovskite CsPbI3. These adducts significantly influence crystallization and the power conversion efficiency of the resulting solar cells.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154525/1/aenm201903365-sup-0001-SuppMat.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154525/2/aenm201903365.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154525/3/aenm201903365_am.pd
CsI‐Antisolvent Adduct Formation in All‐Inorganic Metal Halide Perovskites
The excellent optoelectronic properties demonstrated by hybrid organic/inorganic metal halide perovskites are all predicated on precisely controlling the exact nucleation and crystallization dynamics that occur during film formation. In general, high‐performance thin films are obtained by a method commonly called solvent engineering (or antisolvent quench) processing. The solvent engineering method removes excess solvent, but importantly leaves behind solvent that forms chemical adducts with the lead‐halide precursor salts. These adduct‐based precursor phases control nucleation and the growth of the polycrystalline domains. There has not yet been a comprehensive study comparing the various antisolvents used in different perovskite compositions containing cesium. In addition, there have been no reports of solvent engineering for high efficiency in all‐inorganic perovskites such as CsPbI3. In this work, inorganic perovskite composition CsPbI3 is specifically targeted and unique adducts formed between CsI and precursor solvents and antisolvents are found that have not been observed for other A‐site cation salts. These CsI adducts control nucleation more so than the PbI2–dimethyl sulfoxide (DMSO) adduct and demonstrate how the A‐site plays a significant role in crystallization. The use of methyl acetate (MeOAc) in this solvent engineering approach dictates crystallization through the formation of a CsI–MeOAc adduct and results in solar cells with a power conversion efficiency of 14.4%.It is found that unique adducts form between CsI and dimethyl sulfoxide (DMSO) and certain antisolvents, such as methyl acetate, during film formation of the all‐inorganic perovskite CsPbI3. These adducts significantly influence crystallization and the power conversion efficiency of the resulting solar cells.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154525/1/aenm201903365-sup-0001-SuppMat.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154525/2/aenm201903365.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154525/3/aenm201903365_am.pd
Roadmap on Photovoltaic Absorber Materials for Sustainable Energy Conversion
Photovoltaics (PVs) are a critical technology for curbing growing levels of
anthropogenic greenhouse gas emissions, and meeting increases in future demand
for low-carbon electricity. In order to fulfil ambitions for net-zero carbon
dioxide equivalent (CO2eq) emissions worldwide, the global
cumulative capacity of solar PVs must increase by an order of magnitude from
0.9 TWp in 2021 to 8.5 TWp by 2050 according to the International Renewable
Energy Agency, which is considered to be a highly conservative estimate. In
2020, the Henry Royce Institute brought together the UK PV community to discuss
the critical technological and infrastructure challenges that need to be
overcome to address the vast challenges in accelerating PV deployment. Herein,
we examine the key developments in the global community, especially the
progress made in the field since this earlier roadmap, bringing together
experts primarily from the UK across the breadth of the photovoltaics
community. The focus is both on the challenges in improving the efficiency,
stability and levelized cost of electricity of current technologies for
utility-scale PVs, as well as the fundamental questions in novel technologies
that can have a significant impact on emerging markets, such as indoor PVs,
space PVs, and agrivoltaics. We discuss challenges in advanced metrology and
computational tools, as well as the growing synergies between PVs and solar
fuels, and offer a perspective on the environmental sustainability of the PV
industry. Through this roadmap, we emphasize promising pathways forward in both
the short- and long-term, and for communities working on technologies across a
range of maturity levels to learn from each other.Comment: 160 pages, 21 figure
Recommended from our members
Research data supporting "Oxygen degradation in mesoporous Al2O3 / CH3NH3PbI3-xClx perovskite solar cells - kinetics and mechanisms"
Initial performance and ageing data for solar cells (IV, TPC, TPV). XRD data for aged solar cells.This research data supports “Oxygen degradation in mesoporous Al2O3 / CH3NH3PbI3-xClx perovskite solar cells - kinetics and mechanisms” which has been published in “Advanced Energy Materials”.This work was supported by the EC [grant number EU FP7 - 604032 'MESO'] and EPSRC [grant number EP/J0I7361/1 'SuperSolar Consortium']
Enhanced Hole Extraction in Perovskite Solar Cells Through Carbon Nanotubes
Here, we report the use of polymer-wrapped
carbon nanotubes as
a means to enhance charge extraction through undoped spiro-OMeTAD.
With this approach a good solar cell performance is achieved without
the implementation of conventional doping methods. We demonstrate
that a stratified two-layer architecture of sequentially deposited
layers of carbon nanotubes and spiro-OMeTAD, outperforms a conventional
blend of the hole-conductor and the carbon nanotubes. We also provide
insights into the mechanism of the rapid hole extraction observed
in the two-layer approach
Efficient and Stable Perovskite Solar Cells Using Molybdenum Tris(dithiolene)s as p‑Dopants for Spiro-OMeTAD
Metal halide perovskite
solar cells have now reached efficiencies
of over 22%. To date, the most efficient perovskite solar cells have
the n-i-p device architecture and use 2,2′,7,7′-tetrakis(<i>N,N</i>′-di-<i>p</i>-methoxyphenylamine)-9,9′-spirobifluorene
or poly(triarylamine) as the hole transport material (HTM), which
are typically doped with lithium bis((trifluomethyl)sulfonyl)amide
(Li-TFSI). Li-TFSI is hygroscopic and detrimental to the long-term
performance of the solar cells, limiting its practical use. In this
work, we successfully replace Li-TFSI by molybdenum tris(1-(methoxycarbonyl)-2-(trifluoromethyl)ethane-1,2-dithiolene),
Mo(tfd-CO<sub>2</sub>Me)<sub>3</sub>, or molybdenum tris(1-(trifluoroacetyl)-2-(trifluoromethyl)ethane-1,2-dithiolene),
Mo(tfd-COCF<sub>3</sub>)<sub>3</sub>. With these two dopants, we achieve
stabilized power conversion efficiencies up to 16.7% and 15.7% with
average efficiencies of 14.8% ± 1.1% and 14.4% ± 1.2%, respectively.
Moreover, we observe a significant enhancement of the long-term stability
of perovskite solar cells under 85 °C thermal stressing in air
Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic–Inorganic Lead Halide Perovskites
In a combined theoretical and experimental
work, we investigate
X-ray absorption near-edge structure spectroscopy of the I <i>L</i><sub>3</sub> and the Pb <i>M</i><sub>5</sub> edges
of the methylammonium lead iodide (MAPbI<sub>3</sub>) hybrid inorganic–organic
perovskite and its binary phase PbI<sub>2</sub>. The absorption onsets
are dominated by bound excitons with sizable binding energies of a
few hundred millielectronvolts and pronounced anisotropy. The spectra
of both materials exhibit remarkable similarities, suggesting that
the fingerprints of core excitations in MAPbI<sub>3</sub> are essentially
given by its inorganic component, with negligible influence from the
organic groups. The theoretical analysis complementing experimental
observations provides the conceptual insights required for a full
characterization of this complex material
Hydrophobic Organic Hole Transporters for Improved Moisture Resistance in Metal Halide Perovskite Solar Cells
Solar cells based on organic–inorganic
perovskite semiconductor
materials have recently made rapid improvements in performance, with
the best cells performing at over 20% efficiency. With such rapid
progress, questions such as cost and solar cell stability are becoming
increasingly important to address if this new technology is to reach
commercial deployment. The moisture sensitivity of commonly used organic–inorganic
metal halide perovskites has especially raised concerns. Here, we
demonstrate that the hygroscopic lithium salt commonly used as a dopant
for the hole transport material in perovskite solar cells makes the
top layer of the devices hydrophilic and causes the solar cells to
rapidly degrade in the presence of moisture. By using novel, low cost,
and hydrophobic hole transporters in conjunction with a doping method
incorporating a preoxidized salt of the respective hole transporters,
we are able to prepare efficient perovskite solar cells with greatly
enhanced water resistance