scholarly journals Temperature-Dependent Evolution of Raman Spectra of Methylammonium Lead Halide Perovskites, CH3NH3PbX3 (X = I, Br)

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 626 ◽  
Author(s):  
Kousuke Nakada ◽  
Yuki Matsumoto ◽  
Yukihiro Shimoi ◽  
Koji Yamada ◽  
Yukio Furukawa
Keyword(s):  
Phase Transitions ◽  
Temperature Dependence ◽  
Temperature Dependent ◽  
High Power Conversion Efficiency ◽  
Perovskite Materials ◽  
Hybrid Perovskite ◽  
Temperature Ranges ◽  
Raman Study ◽  
Halide Perovskites ◽  
Motional Narrowing

We present a Raman study on the phase transitions of organic/inorganic hybrid perovskite materials, CH3NH3PbX3 (X = I, Br), which are used as solar cells with high power conversion efficiency. The temperature dependence of the Raman bands of CH3NH3PbX3 (X = I, Br) was measured in the temperature ranges of 290 to 100 K for CH3NH3PbBr3 and 340 to 110 K for CH3NH3PbI3. Broad ν1 bands at ~326 cm−1 for MAPbBr3 and at ~240 cm−1 for MAPbI3 were assigned to the MA–PbX3 cage vibrations. These bands exhibited anomalous temperature dependence, which was attributable to motional narrowing originating from fast changes between the orientational states of CH3NH3+ in the cage. Phase transitions were characterized by changes in the bandwidths and peak positions of the MA–cage vibration and some bands associated with the NH3+ group.

scholarly journals The influence of deuteration on the crystal structure of hybrid halide perovskites: a temperature-dependent neutron diffraction study of FAPbBr3

2020 ◽  
Vol 76 (2) ◽  
pp. 267-274 ◽  
Author(s):  
Alexandra Franz ◽  
Daniel M. Többens ◽  
Frederike Lehmann ◽  
Martin Kärgell ◽  
Susan Schorr
Keyword(s):  
Neutron Diffraction Study ◽  
Neutron Powder Diffraction ◽  
Independent Molecule ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Structural Modifications ◽  
Hybrid Perovskite ◽  
Halide Perovskites ◽  
Structural Solution

This paper discusses the full structural solution of the hybrid perovskite formamidinium lead tribromide (FAPbBr3) and its temperature-dependent phase transitions in the range from 3 K to 300 K using neutron powder diffraction and synchrotron X-ray diffraction. Special emphasis is put on the influence of deuteration on formamidinium, its position in the unit cell and disordering in comparison to fully hydrogenated FAPbBr3. The temperature-dependent measurements show that deuteration critically influences the crystal structures, i.e. results in partially-ordered temperature-dependent structural modifications in which two symmetry-independent molecule positions with additional dislocation of the molecular centre atom and molecular angle inclinations are present.

scholarly journals Solid State Transitions in Alkali Alkanoates: Diffractometric and Conductometric Measurements on Lithium, Sodium and Potassium Propanoates

1979 ◽  
Vol 34 (5) ◽  
pp. 575-578 ◽  
Author(s):  
A. Cingolani ◽  
G. Spinolo ◽  
M. Sanesi
Keyword(s):  
Phase Transitions ◽  
Solid State ◽  
Temperature Dependence ◽  
Powder Diffraction ◽  
State Transitions ◽  
Potassium Salts ◽  
Crystalline Phases ◽  
X Ray ◽  
Temperature Ranges ◽  
Sodium And Potassium

Abstract Conductometric measurements on solid lithium, sodium and potassium propanoates and X-ray powder diffraction measurements on the sodium and potassium salts have been performed over temperature ranges including solid state transitions. The temperature dependence of the transport and lattice parameters of the different crystalline phases and the changes of the same parameters in correspondence with phase transitions have been put into evidence.

scholarly journals Coherence lifetime broadened optical transitions in a 2 atom diameter HgTe nanowire: a temperature dependent resonance Raman study

RSC Advances ◽  
2016 ◽  
Vol 6 (98) ◽  
pp. 95387-95395 ◽  
Author(s):  
Joseph H. Spencer ◽  
David C. Smith ◽  
Liam P. McDonnell ◽  
Jeremy Sloan ◽  
Reza J. Kashtiban
Keyword(s):  
Raman Scattering ◽  
Temperature Dependence ◽  
Resonance Raman ◽  
Strong Temperature Dependence ◽  
Optical Transitions ◽  
Temperature Dependent ◽  
Raman Study ◽  
Electronic Coherence ◽  
Excitonic Effects

The paper sets out the role of electronic coherence in the strong temperature dependence of the intensity of Raman scattering from two atom diameter HgTe nanowires. It argues the behavior is likely common in extreme nanowires, and possibly due to excitonic effects.

Anomalous Temperature Dependence of the Hall Coefficient of Heavily Al-Doped 4H-SiC Epilayers in the Band Conduction Region

2020 ◽  
Vol 1004 ◽  
pp. 215-223
Author(s):  
Hideharu Matsuura ◽  
Rinya Nishihata ◽  
Akinobu Takeshita ◽  
Kohei Ogawa ◽  
Tatsuya Imamura ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Hall Coefficient ◽  
Bipolar Transistors ◽  
Hopping Conduction ◽  
Insulated Gate Bipolar Transistors ◽  
Temperature Dependent ◽  
Anomalous Temperature ◽  
Temperature Ranges ◽  
P Type ◽  
Band Conduction

We investigate the temperature dependence of the resistivity and Hall coefficient for heavily Al-doped p-type 4H-SiC epilayers with Al concentrations (C_Al) of > 2E19 cm^−3, which are substrates for the collectors of insulated-gate bipolar transistors. The signs of the measured Hall co- efficients (R_H) changed from positive to negative at low temperatures. For epilayers with C_Al values of < 3E19 cm^−3, a negative R_H was observed in the hopping conduction region. In contrast, for epilayers with C_Al values of > 3E19 cm^−3, a negative R_H was observed in not only the hopping conduction region but also the band conduction region, which is a striking feature because the movement of free holes in the valence band should make R_H positive. For an epilayer with C_Al of 1.8E20 cm^−3, the sign of R_H clearly changed three times in the band conduction region. Moreover, the activation energies of the temperature-dependent R_H values were similar to those of the temperature-dependent resistivity in the corresponding temperature ranges, irrespective of the conduction mechanisms (band and hopping conduction).

scholarly journals Raman Spectroscopy Studies on the Barocaloric Hybrid Perovskite [(CH3)4N][Cd(N3)3]

Molecules ◽  
2020 ◽  
Vol 25 (20) ◽  
pp. 4754
Author(s):  
Rosivaldo Xavier da Silva ◽  
Carlos William de Araujo Paschoal ◽  
Clenilton Costa dos Santos ◽  
Alberto García-Fernández ◽  
Jorge Salgado-Beceiro ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Phase Transitions ◽  
Intermolecular Interactions ◽  
Structural Phase ◽  
Blue Shift ◽  
Temperature Dependent ◽  
Scanning Calorimetry ◽  
Hybrid Perovskite ◽  
Entropy Variation ◽  
Spectroscopy Studies

Temperature-dependent Raman scattering and differential scanning calorimetry were applied to the study of the hybrid organic-inorganic azide-perovskite [(CH3)4N][Cd(N3)3], a compound with multiple structural phase transitions as a function of temperature. A significant entropy variation was observed associated to such phase transitions, |∆S| ~ 62.09 J·kg−1 K−1, together with both a positive high barocaloric (BC) coefficient |δTt/δP| ~ 12.39 K kbar−1 and an inverse barocaloric (BC) coefficient |δTt/δP| ~ −6.52 kbar−1, features that render this compound interesting for barocaloric applications. As for the obtained Raman spectra, they revealed that molecular vibrations associated to the NC4, N3– and CH3 molecular groups exhibit clear anomalies during the phase transitions, which include splits and discontinuity in the phonon wavenumber and lifetime. Furthermore, variation of the TMA+ and N3– modes with temperature revealed that while some modes follow the conventional red shift upon heating, others exhibit an unconventional blue shift, a result which was related to the weakening of the intermolecular interactions between the TMA (tetramethylammonium) cations and the azide ligands and the concomitant strengthening of the intramolecular bondings. Therefore, these studies show that Raman spectroscopy is a powerful tool to gain information about phase transitions, structures and intermolecular interactions between the A-cation and the framework, even in complex hybrid organic-inorganic perovskites with highly disordered phases.

scholarly journals Regulation of the luminescence mechanism of two-dimensional tin halide perovskites

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Tianju Zhang ◽  
Chaocheng Zhou ◽  
Xuezhen Feng ◽  
Ningning Dong ◽  
Hong Chen ◽  
...  
Keyword(s):  
Transient Absorption ◽  
Phonon Scattering ◽  
Potential Scattering ◽  
Transient Absorption Spectroscopy ◽  
Two Dimensional ◽  
Temperature Dependent ◽  
Control Engineering ◽  
Perovskite Materials ◽  
Halide Perovskites ◽  
Charged Defects

AbstractTwo-dimensional (2D) Sn-based perovskites are a kind of non-toxic environment-friendly luminescent material. However, the research on the luminescence mechanism of this type of perovskite is still very controversial, which greatly limits the further improvement and application of the luminescence performance. At present, the focus of controversy is defects and phonon scattering rates. In this work, we combine the organic cation control engineering with temperature-dependent transient absorption spectroscopy to systematically study the interband exciton relaxation pathways in layered A2SnI4 (A = PEA+, BA+, HA+, and OA+) structures. It is revealed that exciton-phonon scattering and exciton-defect scattering have different effects on exciton relaxation. Our study further confirms that the deformation potential scattering by charged defects, not by the non-polar optical phonons, dominates the excitons interband relaxation, which is largely different from the Pb-based perovskites. These results enhance the understanding of the origin of the non-radiative pathway in Sn-based perovskite materials.

Engineering Hybrid Perovskite Materials for Spectroscopic Sensing of Ionizing Radiation

2019 ◽  
Author(s):  
Eric Lukosi ◽  
Mahshid Ahmadi ◽  
Travis Smith ◽  
Ryan Tan ◽  
Bogdan Dryzhakov ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Perovskite Materials ◽  
Hybrid Perovskite

Studies on the Temperature Stability of Pure and Doped Triglycine Sulphate Crystals Using TGA/DTA

2020 ◽  
Vol 10 (3) ◽  
pp. 206-212
Author(s):  
Vijeesh Padmanabhan ◽  
Maneesha P. Madhu ◽  
Supriya M. Hariharan
Keyword(s):  
Thermal Analysis ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Temperature Stability ◽  
Bandgap Energy ◽  
Dsc Analysis ◽  
Slow Cooling ◽  
As Doping ◽  
Similar Dependence ◽  
Temperature Ranges

Aim: To study the temperature stability of TGS doped with ZnSO4, CdCl2, BaCl2, and compare it with that of pure TGS. Objectives: Synthesizing pure and doped TGS and studying their temperature dependence using TGA, DTA, and DSC analysis. Methods: Slow cooling solution growth was used to grow single crystals of pure and doped TGS. The TGA, DTA and DSC analysis was conducted for determining the temperature stability. Results: The thermal analysis of pure and doped TGS shows that the doped samples show a similar dependence on temperature as pure TGS. The temperature of decomposition of pure and doped samples (BTGS, ZTGS, CdTGS) was 226.60°C, 228.38°C, 229.13°C, and 239.13°C respectively. The melting onset of these samples was 214.51°C, 216.04°C, 217.69°C and 216.04°C respectively. Conclusion: The study shows that doping TGS with the above three described materials did not alter their temperature stability considerably. It is a good result as doping TGS, for varying its characteristics like absorbance, reflectance, bandgap energy, etc., which did not alter its temperature stability. Therefore, TGS doped with the above three dopants can be used at the same temperature ranges as of pure TGS but with much-improved efficiency.

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