A5004105452- Perovskite Materials and Applications
- Solid-state spectroscopy and crystallography
- Crystallization and Solubility Studies
- Optical properties and cooling technologies in crystalline materials
- X-ray Diffraction in Crystallography
- Thermal Expansion and Ionic Conductivity
- Crystallography and molecular interactions
- Organic and Molecular Conductors Research
- Advanced Thermoelectric Materials and Devices
- Quantum Dots Synthesis And Properties
- Nonlinear Optical Materials Research
- Electronic and Structural Properties of Oxides
- Multiferroics and related materials
- Advanced Photocatalysis Techniques
- Ferroelectric and Piezoelectric Materials
- Coral and Marine Ecosystems Studies
- Chalcogenide Semiconductor Thin Films
University of Bath
2015-2019
Centre for Sustainable Energy
2018
University of Bristol
2014
Solar cells composed of methylammonium lead iodide perovskite (MAPI) are notorious for their sensitivity to moisture. We show that (i) hydrated crystal phases formed when MAPI is exposed water vapor at room temperature and (ii) these phase changes fully reversed the material subsequently dried. The reversible formation CH3NH3PbI3·H2O followed by (CH3NH3)4PbI6·2H2O (upon long exposure times) was observed using time-resolved XRD ellipsometry thin films prepared "solvent engineering", single...
The methylammonium cation in [CH3NH3]PbI3 demonstrates increasing positional disorder on heating from 100 K to 352 K. In the tetragonal phase, stable between 165 and 327 K, is disordered over four sites directed toward faces of distorted cubic [PbI3](-) framework migrates towards cavity centre with temperature.
The hybrid halide perovskite ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}{\mathrm{PbI}}_{3}$ exhibits a complex structural behavior, with successive transitions between orthorhombic, tetragonal, and cubic polymorphs around 165 327 K. Herein we report first-principles lattice dynamics (phonon spectrum) for each phase of ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}{\mathrm{PbI}}_{3}$. equilibrium structures compare well to solutions temperature-dependent powder neutron diffraction. By following the normal...
The structure of black formamidinium lead halide, α-[HC(NH2)2]PbI3, at 298 K has been refined from high resolution neutron powder diffraction data and found to adopt a cubic perovskite unit cell, = 6.3620(8) Å. trigonal planar [HC(NH2)2]+ cations lie in the central mirror plane cell with disordered over 12 possible sites arranged so that C–H bond is directed into cube face, whereas −NH2 groups hydrogen (NH···I 2.75–3.00 Å) iodide atoms [PbI3]− framework. High atomic displacement parameters...
The optical constants of methylammonium lead halide single crystals CH3NH3PbX3 (X = I, Br, Cl) are interpreted with high level ab initio calculations using the relativistic quasiparticle self-consistent GW approximation (QSGW). Good agreement between derived from QSGW and those obtained spectroscopic ellipsometry enables assignment spectral features to their respective inter-band transitions. We show that transition highest valence band (VB) lowest conduction (CB) is responsible for almost...
Raman and THz spectra of CH<sub>3</sub>NH<sub>3</sub>PbX<sub>3</sub> interpreted with a catalogue computed vibrations their influence on heat electrical transport.
The phase and structural behaviours of the hybrid perovskites FA<sub>x</sub>MA<sub>1−x</sub>PbI<sub>3</sub>as a function composition temperature have been determined.
A greater understanding of the structure–property relationships hybrid perovskites for solar cells is crucial enhancing their performance. The low-temperature phases formamidinium lead iodide (FAPbI3) have been investigated using rapid neutron powder diffraction. On cooling, metastable α-polymorph descends in symmetry from cubic unit cell phase present at room temperature through two successive transitions. Between 285 and 140 K a tetragonal phase, adopting space group P4/mbm, confirmed...
Thin films of the mixed A-cation phase MA<sub>1−x</sub>FA<sub>x</sub>PbI<sub>3</sub> have been shown experimentally and computationally to greater kinetic thermodynamic stability towards decomposition.
Lead halide perovskites are causing a change of paradigm in photovoltaics. Among other peculiarities, these exhibit an atypical temperature dependence the fundamental optical gap: It decreases energy with decreasing temperature. So far reports ascribe such behavior to particularly strong electron-phonon renormalization band gap, neglecting completely contributions from thermal expansion effects. However, high pressure experiments performed, for instance, on archetypal perovskite MAPbI$_3$,...
Abstract The photoelectrochemical properties of LaFeO 3 nanoparticles are discussed for the first time. Highly phase‐pure particles prepared by a novel ionic‐liquid‐based method characterized (60±14) nm mean size and band gap (2.56±0.07) eV. Thin films deposited screen printing exhibit photocurrent responses associated with hydrogen generation at potential up to 1 V more positive than formal potential. Analysis as function photon flux bias suggest that hole‐collection efficiency back contact...
The structural phase behavior of high-quality single crystals methylammonium lead iodide (CH3NH3PbI3 or MAPbI3) was revisited by combining Raman scattering and photoluminescence (PL) measurements under high hydrostatic pressure up to ca. 10 GPa. were specially grown with the final thickness needed for experiments, retaining their quality due a less invasive preparation procedure, which avoids sample thinning. Both PL spectra show simultaneous changes in profiles that indicate occurrence...
The structural chemistry of hybrid organic-inorganic lead iodide materials has become increasing significance for energy applications since the discovery and development perovskite solar cells based on methylammonium iodide. Seven new compounds have been synthesized structurally characterized using single-crystal X-ray diffraction. units in templated with bipyridyl, 1,2-bis(4-pyridyl)ethane, 1,2-di(4-pyridyl)ethylene imidazole adopt one-dimensional chain structures, while crystallization...