Fast Ionic Transport in Solids

Farrington, G. C.; Briant, J.L.

doi:10.1126/science.204.4400.1371

Cited by 155 publications

(85 citation statements)

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“…Detailed DFT calculations have been provided by Mosconi et al [177] and Meloni et al [130] The latter calculated the migrating pathways for each defect, including iodide vacancies, MA vacancies, Pb vacancies, and iodide interstitials, as shown in Figure 10c-e, respectively. The migration pathways of individual ions/defects are consistent with the ones proposed by Eames et al [171] Apart from hopping through point defects (Schottky and Frenkel defects) within the crystal lattice, [178] as shown in Figure 10f,g, a range of other possible ion migration channels can exist. Yuan et al suggest local lattice distortion, induced through charges or additional impurity atoms, lightinduced softening, and piezoelectric effects, as shown in Figure 10h-l. [168] Furthermore, grain boundaries (GB) that possess a large density of defects may play an even more important role, illustrated in Figure 10k.…”

Section: Ion Migration Processsupporting

confidence: 72%

“…[130,171,177] Herein, the ionic transport is described as a hopping mechanism, i.e., jumping between neighboring sites. [178] As shown in Figure 10a,b, i) MA + ions migrate into a nearby vacant cage, ii) Pb 2+ ions migrate via the diagonal direction, whilst iii) iodide ions move along an octahedron in the Pb-I plane. [171] The migration of these ions requires an energy to open the PbX 3 framework, which acts as a barrier for the ionic migration.…”

Section: Ion Migration Processmentioning

confidence: 99%

“…[178] The movement of ions is facilitated by a hopping mechanism in the atomic lattices via defect states (i.e., vacancies, interstitials, etc.). [183] This hopping process to the neighboring sites requires energy, i.e., an activation energy, E a , to overcome the barriers.…”

Section: Wwwadvancedsciencenewscommentioning

confidence: 99%

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Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

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Schlipf

Cheng

et al. 2017

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following statement: These materials can be processed from solution and yet exhibit optoelectronic materials properties described in classic solid-state physics textbooks. This unprecedented combination has led to photovoltaic devices that can be processed at room temperature and achieve performance levels similar to industry giant polycrystalline silicon, from a starting point of 3.8% in 2009. [1][2][3][4] The first light-emitting electrochemical cells [5] and diodes [6][7][8] have also been introduced recently, leading to tunable light emission spectra and internal quantum efficiencies exceeding 15%.The road towards these achievements has been marked by a constant improvement of perovskite deposition techniques fueled by our increasing understanding of the crystallization processes. The choice of deposition technique, either from solution or vapor, and the composition and order in which precursor species are applied has a great influence on the crystallization kinetics. Here, one can distinguish one-step methods where the perovskite is formed from a precursor mixture dissolved in a common solution, and two-step methods where the inorganic compound is deposited first and transformed to the perovskite phase later by addition of the organic constituents. [9][10][11] Furthermore, many parameters during processing can have an effect on the crystallization mechanism and consequently on film morphology, such as the choice of solvents, concentrations and processing additives that are often not incorporated into the final product. [11][12][13] We discuss this aspect in Section 2, where we focus our attention on the most commonly employed solution-based techniques. Additionally, as for any new technology trying to displace an incumbent technology, higher efficiencies, lower costs, reproducibility, stability, and sustainability are paramount. In particular, reproducibility has been a major challenge in perovskite solar cells from the beginning: small variations in morphology, like crystal size, film roughness, and pinholes can have detrimental effects on photovoltaic performance. [14] On the other hand, current-voltage measurements often showed a hysteresis that is rarely seen in other photovoltaic technologies. [15] These topics are highlighted in Sections 3 and 4. Finally, in Section 5 we discuss the framework for market introduction, such as cost reduction by choosing low-cost charge transport layers, or how the lifetime of perovskite absorbers can be extended by the choice of materials composition.Hybrid metal halide perovskites have become one of the hottest topics in optoelectronic materials research in recent years. Not only have they surpassed everyone's expectations and achieved similar performance as tried and true polycrystalline silicon photovoltaic devices, but they are also finding applications in a variety of different fields, including lighting. The main advantages of hybrid metal halide perovskites are simple processability, compatible with large-scale solution processing such as roll-to-roll printing, a...

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Section: Ion Migration Processsupporting

confidence: 72%

Section: Ion Migration Processmentioning

confidence: 99%

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Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

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“…These respective ions will therefore be present in maghemite derived from magnetite prepared by precipitation of iron(I1)-(111) mixtures with hot aqueous NaOH or KOH, since this magnetite is not stoichiometric Fe304 but rather a solid solution of Fe304 in maghemite, represented above as Fe3-,04-, but in fact containing moisture (and hence protons in cation sites) roughly in proportion to x. Alkali-metal ferrites with the spinel (LiFe,O,, NaFe,O,) (24,49) or other (KFe,O,) (49,50) structures, or of the "p-alumina" type (1 + y)M20.1 lFe203 (M = Na, K) which retains some elements of the spinel structure (51)(52)(53)(54)(55)(56), are well known, as are some mixed-alkali-metal analogues (5 1, 57). The maghemite samples H,-8M8Fe,08 prepared in this study contained far less alkali metal ion than these ferrites, since 6 was always less than 0.1, but we note that the saturation magnetization of maghemite decreased as 6 increased, in accordance with the lack of ferromagnetism at room temperature in ferrites such as KFe,O,, KFe7011, and KFe,,017 (50,52 For personal use only.…”

Section: Discussionmentioning

confidence: 99%

Kinetics of the magnetite–maghemite–hematite transformation, with special reference to hydrothermal systems

Swaddle¹,

Oltmann²

1980

Can. J. Chem.

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. Maghemite, prepared in the usual way (but with exclusion of silica, e.g., from glassware) by precipitation of non-stoichiometric magnetite Fe3-,O,-, in aqueous MOH (M = Na, K) followed by air oxidation, picks up moisture from the air to reach the limiting composition MsH,-sFe50,. where 6 -0.02-0.03 for fresh material, but changes under hydrothermal conditions because of ion exchange. Despite the role of absorbed moisture in stabilizing maghernite, formation of the latter from Fe3-,O,-, is markedly retarded, and its decomposition to u-Fe,03 greatly accelerated, under hydrothermal conditions relative to the rates of the corresponding reactions of the dry solids. The rate of hydrothermal decomposition of maghemite is strongly retarded by silica. Over the range 160-187°C at least, silica-free maghemite decomposes in water according to the empirical equation -In ( I -a ) = (kt)", whereu is the fractional extent of decomposition. and 11 -2.5 for neutral water (with k = 1.3 x s-I at 160°C and 3.1 x 10-5s-' at 175°C) but approaches unity, without major effects on the overall time-scale of reaction, at high [MOH]. The mechanistic significance of these and previous results are considered; the hydrothermal conversion of maghemite to hematite evidently proceeds by ii dissolution-reprecipitation sequence. THOMAS WILSON SWADDLE et P~~I L L I P~L T M A N N .Can. J . Chem. 58, 1763 (1980). La maghemite. preparee de manitre habituelle (mais avec elimination de la silice par exemple celle de la verrerie) par precipitation de la magnetite non stoechiometrique Fe,-,O,_, dans du MOH aqueux (M = Na, K) suivie d'une oxydation a I'air, absorbe I'humiditC de I'air pour atteindre une composition limite de MsHI+,Fe5O, ou 6 -0.02-0.03 pour le produit fr-ais, mais il se produit des changements dans des conditions hydrothermiques pa; suite de I'echange d'ions. En depit du r6le de I'humidite absorbee en tant que stabilisatrice de la maghernite, la formation de cette derniere B partir de Fe3+,0,_, est fortement retiirdee et sa dCcomposition en Fe203 u est grandement accClerCe dans des conditions hydrothermiques s'apparentant aux vitesses des reactions correspondantes des solides secs. La vitesse de decomposition hydrothermique de la maghemite est fortement retardee par la silice. Au moins dans I'intervalle de 160-187"C, la maghemite depourvue de silice se decompose dans I'eau selon I'equation empirique In (1 -a ) =

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“…Figure 23 is an Arrhenius plot of the DC ionic conductivity, as published by Farrington and Briant [87]. The conductivities were measured along the conduction planes of a single crystal of Na 1.68 Mg 0.67 Al 10.4 O 17.1 .…”

Section: Structure and Ion Dynamics In Na-β -Aluminamentioning

confidence: 99%