Browse
Submit Data
Databases
API
Help

Dataset Information

38 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Large Thermal Motion in Halide Perovskites.

ABSTRACT: Solar cells based on hybrid perovskites have shown high efficiency while possessing simple processing methods. To gain a fundamental understanding of their properties on an atomic level, we investigate single crystals of CH₃NH₃PbI₃ with a narrow transition (~5?K) near 327?K. Temperature dependent structural measurements reveal a persistent tetragonal structure with smooth changes in the atomic displacement parameters (ADPs) on crossing T*. We show that the ADPs for I ions yield extended flat regions in the potential wells consistent with the measured large thermal expansion parameter. Molecular dynamics simulations reveal that this material exhibits significant asymmetries in the Pb-I pair distribution functions. We also show that the intrinsically enhanced freedom of motion of the iodine atoms enables large deformations. This flexibility (softness) of the atomic structure results in highly localized atomic relaxation about defects and hence accounts for both the high carrier mobility as well as the structural instability.

SUBMITTER: Tyson TA

PROVIDER: S-EPMC5571225 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Large Thermal Motion in Halide Perovskites.

Tyson T A TA Gao W W Chen Y-S YS Ghose S S Yan Y Y

Scientific reports 20170824 1

Solar cells based on hybrid perovskites have shown high efficiency while possessing simple processing methods. To gain a fundamental understanding of their properties on an atomic level, we investigate single crystals of CH3NH3PbI3 with a narrow transition (~5 K) near 327 K. Temperature dependent structural measurements reveal a persistent tetragonal structure with smooth changes in the atomic displacement parameters (ADPs) on crossing T*. We show that the ADPs f ...[more]

PMID: 28839173

Similar Datasets

Large polarons in lead halide perovskites.

Project description:Lead halide perovskites show marked defect tolerance responsible for their excellent optoelectronic properties. These properties might be explained by the formation of large polarons, but how they are formed and whether organic cations are essential remain open questions. We provide a direct time domain view of large polaron formation in single-crystal lead bromide perovskites CH3NH3PbBr3 and CsPbBr3. We found that large polaron forms predominantly from the deformation of the PbBr3- frameworks, irrespective of the cation type. The difference lies in the polaron formation time, which, in CH3NH3PbBr3 (0.3 ps), is less than half of that in CsPbBr3 (0.7 ps). First-principles calculations confirm large polaron formation, identify the Pb-Br-Pb deformation modes as responsible, and explain quantitatively the rate difference between CH3NH3PbBr3 and CsPbBr3. The findings reveal the general advantage of the soft [PbX3]- sublattice in charge carrier protection and suggest that there is likely no mechanistic limitations in using all-inorganic or mixed-cation lead halide perovskites to overcome instability problems and to tune the balance between charge carrier protection and mobility.

| S-EPMC5553817 | biostudies-other

Ultralow thermal conductivity in all-inorganic halide perovskites.

Project description:Controlling the flow of thermal energy is crucial to numerous applications ranging from microelectronic devices to energy storage and energy conversion devices. Here, we report ultralow lattice thermal conductivities of solution-synthesized, single-crystalline all-inorganic halide perovskite nanowires composed of CsPbI3 (0.45 ± 0.05 W·m-1·K-1), CsPbBr3 (0.42 ± 0.04 W·m-1·K-1), and CsSnI3 (0.38 ± 0.04 W·m-1·K-1). We attribute this ultralow thermal conductivity to the cluster rattling mechanism, wherein strong optical-acoustic phonon scatterings are driven by a mixture of 0D/1D/2D collective motions. Remarkably, CsSnI3 possesses a rare combination of ultralow thermal conductivity, high electrical conductivity (282 S·cm-1), and high hole mobility (394 cm2·V-1·s-1). The unique thermal transport properties in all-inorganic halide perovskites hold promise for diverse applications such as phononic and thermoelectric devices. Furthermore, the insights obtained from this work suggest an opportunity to discover low thermal conductivity materials among unexplored inorganic crystals beyond caged and layered structures.

| S-EPMC5565476 | biostudies-literature

Design Principles of Large Cation Incorporation in Halide Perovskites.

Project description:Perovskites have stood out as excellent photoactive materials with high efficiencies and stabilities, achieved via cation mixing techniques. Overcoming challenges to the stabilization of Perovskite solar cells calls for the development of design principles of large cation incorporation in halide perovskite to accelerate the discovery of optimal stable compositions. Large fluorinated organic cations incorporation is an attractive method for enhancing the intrinsic stability of halide perovskites due to their high dipole moment and moisture-resistant nature. However, a fluorinated cation has a larger ionic size than its non-fluorinated counterpart, falling within the upper boundary of the mixed-cation incorporation. Here, we report on the intrinsic stability of mixed Methylammonium (MA) lead halides at different concentrations of large cation incorporation, namely, ehtylammonium (EA; [CH3CH2NH3]+) and 2-fluoroethylammonium (FEA; [CH2FCH2NH3]+). Density functional theory (DFT) calculations of the enthalpy of the mixing and analysis of the perovskite structural features enable us to narrow down the compositional search domain for EA and FEA cations around concentrations that preserve the perovskite structure while pointing towards the maximal stability. This work paves the way to developing design principles of a large cation mixture guided by data analysis of DFT data. Finally, we present the automated search of the minimum enthalpy of mixing by implementing Bayesian optimization over the compositional search domain. We introduce and validate an automated workflow designed to accelerate the compositional search, enabling researchers to cut down the computational expense and bias to search for optimal compositions.

| S-EPMC8539499 | biostudies-literature

Atomic-Level Description of Thermal Fluctuations in Inorganic Lead Halide Perovskites.

Project description:A comprehensive microscopic description of thermally induced distortions in lead halide perovskites is crucial for their realistic applications, yet still unclear. Here, we quantify the effects of thermal activation in CsPbBr3 nanocrystals across length scales with atomic-level precision, and we provide a framework for the description of phase transitions therein, beyond the simplistic picture of unit-cell symmetry increase upon heating. The temperature increase significantly enhances the short-range structural distortions of the lead halide framework as a consequence of the phonon anharmonicity, which causes the excess free energy surface to change as a function of temperature. As a result, phase transitions can be rationalized via the soft-mode model, which also describes displacive thermal phase transitions in oxide perovskites. Our findings allow to reconcile temperature-dependent modifications of physical properties, such as changes in the optical band gap, that are incompatible with the perovskite time- and space-average structures.

| S-EPMC9036582 | biostudies-literature

Indirect tail states formation by thermal-induced polar fluctuations in halide perovskites.

Project description:Halide perovskites possess enormous potential for various optoelectronic applications. Presently, a clear understanding of the interplay between the lattice and electronic effects is still elusive. Specifically, the weakly absorbing tail states and dual emission from perovskites are not satisfactorily described by existing theories based on the Urbach tail and reabsorption effect. Herein, through temperature-dependent and time-resolved spectroscopy on metal halide perovskite single crystals with organic or inorganic A-site cations, we confirm the existence of indirect tail states below the direct transition edge to arise from a dynamical Rashba splitting effect, caused by the PbBr6 octahedral thermal polar distortions at elevated temperatures. This dynamic effect is distinct from the static Rashba splitting effect, caused by non-spherical A-site cations or surface induced lattice distortions. Our findings shed fresh perspectives on the electronic-lattice relations paramount for the design and optimization of emergent perovskites, revealing broad implications for light harvesting/photo-detection and light emission/lasing applications.

| S-EPMC6351600 | biostudies-literature

On the Thermal and Thermodynamic (In)Stability of Methylammonium Lead Halide Perovskites.

Project description:The interest of the scientific community on methylammonium lead halide perovskites (MAPbX3, X = Cl, Br, I) for hybrid organic-inorganic solar cells has grown exponentially since the first report in 2009. This fact is clearly justified by the very high efficiencies attainable (reaching 20% in lab scale devices) at a fraction of the cost of conventional photovoltaics. However, many problems must be solved before a market introduction of these devices can be envisaged. Perhaps the most important to be addressed is the lack of information regarding the thermal and thermodynamic stability of the materials towards decomposition, which are intrinsic properties of them and which can seriously limit or even exclude their use in real devices. In this work we present and discuss the results we obtained using non-ambient X-ray diffraction, Knudsen effusion-mass spectrometry (KEMS) and Knudsen effusion mass loss (KEML) techniques on MAPbCl3, MAPbBr3 and MAPbI3. The measurements demonstrate that all the materials decompose to the corresponding solid lead (II) halide and gaseous methylamine and hydrogen halide, and the decomposition is well detectable even at moderate temperatures (~60 °C). Our results suggest that these materials may be problematic for long term operation of solar devices.

| S-EPMC4992962 | biostudies-literature

Bromine Incorporation Affects Phase Transformations and Thermal Stability of Lead Halide Perovskites.

Project description:Mixed-cation and mixed-halide lead halide perovskites show great potential for their application in photovoltaics. Many of the high-performance compositions are made of cesium, formamidinium, lead, iodine, and bromine. However, incorporating bromine in iodine-rich compositions and its effects on the thermal stability of the perovskite structure has not been thoroughly studied. In this work, we study how replacing iodine with bromine in the state-of-the-art Cs0.17FA0.83PbI3 perovskite composition leads to different dynamics in the phase transformations as a function of temperature. Through a combination of structural characterization, cathodoluminescence mapping, X-ray photoelectron spectroscopy, and first-principles calculations, we reveal that the incorporation of bromine reduces the thermodynamic phase stability of the films and shifts the products of phase transformations. Our results suggest that bromine-driven vacancy formation during high temperature exposure leads to irreversible transformations into PbI2, whereas materials with only iodine go through transformations into hexagonal polytypes, such as the 4H-FAPbI3 phase. This work sheds light on the structural impacts of adding bromine on thermodynamic phase stability and provides new insights into the importance of understanding the complexity of phase transformations and secondary phases in mixed-cation and mixed-halide systems.

| S-EPMC11240253 | biostudies-literature

Sensitivity of Nitrogen K-Edge X-ray Absorption to Halide Substitution and Thermal Fluctuations in Methylammonium Lead-Halide Perovskites.

Project description:The performance of hybrid perovskite materials in solar cells crucially depends on their electronic properties, and it is important to investigate contributions to the total electronic structure from specific components in the material. In a combined theoretical and experimental study of CH3NH3PbI3-methylammonium lead triiodide (MAPI)-and its bromide cousin CH3NH3PbBr3 (MAPB), we analyze nitrogen K-edge (N 1s-to-2p*) X-ray absorption (XA) spectra measured in MAPI and MAPB single crystals. This permits comparison of spectral features to the local character of unoccupied molecular orbitals on the CH3NH3 + (MA+) counterions and allows us to investigate how thermal fluctuations, hydrogen bonding, and halide-ion substitution influence the XA spectra as a measure of the local electronic structure. In agreement with the experiment, the simulated spectra for MAPI and MAPB show close similarity, except that the MAPB spectral features are blue-shifted by +0.31 eV. The shift is shown to arise from the intrinsic difference in the electronic structure of the two halide atoms rather than from structural differences between the materials. In addition, from the spectral sampling analysis of molecular dynamics simulations, clear correlations between geometric descriptors (N-C, N-H, and H···I/Br distances) and spectral features are identified and used to explain the spectral shapes.

| S-EPMC8162417 | biostudies-literature

Ferroelectricity-free lead halide perovskites.

Project description:Direct piezoelectric force microscopy (DPFM) is employed to examine whether or not lead halide perovskites exhibit ferroelectricity. Compared to conventional piezoelectric force microscopy, DPFM is a novel technique capable of measuring piezoelectricity directly. This fact is fundamental to be able to examine the existence of ferroelectricity in lead halide perovskites, an issue that has been under debate for several years. DPFM is used to detect the current signals, i.e. changes in the charge distribution under the influence of the scan direction and applied force of the atomic force microscope (AFM) tip in contact mode. For comparison, (i) we use DPFM on lead halide perovskites and well-known ferroelectric materials (i.e. periodically poled lithium niobate and lead zirconate titanate); and (ii) we conduct parallel experiments on MAPbI3 films of different grain sizes, film thicknesses, substrates, and textures using DPFM as well as piezoelectric force microscopy (PFM) and electrostatic force microscopy (EFM). In contrast to previous work that claimed there were ferroelectric domains in MAPbI3 perovskite films, our work shows that the studied perovskite films Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 and MAPbI3 are ferroelectricity-free. The observed current profiles of lead halide perovskites possibly originate from ion migration that happens under an applied electrical bias and in strained samples under mechanical stress. This work provides a deeper understanding of the fundamental physical properties of the organic-inorganic lead halide perovskites and solves a longstanding dispute about their non-ferroelectric character: an issue of high relevance for optoelectronic and photovoltaic applications.

| S-EPMC8522734 | biostudies-literature

Magnetizing lead-free halide double perovskites.

Project description:Spintronics holds great potential for next-generation high-speed and low-power consumption information technology. Recently, lead halide perovskites (LHPs), which have gained great success in optoelectronics, also show interesting magnetic properties. However, the spin-related properties in LHPs originate from the spin-orbit coupling of Pb, limiting further development of these materials in spintronics. Here, we demonstrate a new generation of halide perovskites, by alloying magnetic elements into optoelectronic double perovskites, which provide rich chemical and structural diversities to host different magnetic elements. In our iron-alloyed double perovskite, Cs2Ag(Bi:Fe)Br6, Fe3+ replaces Bi3+ and forms FeBr6 clusters that homogenously distribute throughout the double perovskite crystals. We observe a strong temperature-dependent magnetic response at temperatures below 30 K, which is tentatively attributed to a weak ferromagnetic or antiferromagnetic response from localized regions. We anticipate that this work will stimulate future efforts in exploring this simple yet efficient approach to develop new spintronic materials based on lead-free double perovskites.

| S-EPMC7673701 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data