Lattice Dynamics

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Issue 36, Previous Article Next Article. From the journal: Soft Matter. Non-affine lattice dynamics of defective fcc crystals. You have access to this article. Please wait while we load your content Something went wrong. Advanced Search. Article Navigation. Close mobile search navigation Article navigation. Volume 63, Number Previous Article Next Article.

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Other December 01, Lattice dynamics of forsterite K. Iishi K. Google Scholar. American Mineralogist 63 : Article history first online:. This content is PDF only. Please click on the PDF icon to access. We identify the microscopic transport mechanisms, and find facile vacancy-assisted migration of iodide ions with an activation energy of 0.

The results of this combined computational and exptl. Semiconductor Optics , 1 st ed. The family of org. There has been intensive development of cells based on the archetypal methylammonium MA and recently introduced formamidinium FA materials, however, there is still considerable controversy over their fundamental electronic properties.

Introduction to lattice dynamics

The values of the exciton binding energy are in the range meV in the low temp. Solar cells based on the org. Fundamental to understanding the operation of these devices is the exciton binding energy, which has proved both difficult to measure directly and controversial. We demonstrate that by using very high magnetic fields it is possible to make an accurate and direct spectroscopic measurement of the exciton binding energy, which we find to be only 16 meV at low temps. In the room-temp. Our work provides crucial information about the photophysics of these materials, which will in turn allow improved optoelectronic device operation and better understanding of their electronic properties.

Nature communications , 9 1 , ISSN:. Photovoltaic devices based on metal halide perovskites are rapidly improving in efficiency.

Understanding Phonon Transport Using Lattice Dynamics and Molecular Dynamics – Asegun Henry Part 1

Once the Shockley-Queisser limit is reached, charge-carrier extraction will be limited only by radiative bimolecular recombination of electrons with holes. Yet, this fundamental process, and its link with material stoichiometry, is still poorly understood. Here we show that bimolecular charge-carrier recombination in methylammonium lead triiodide perovskite can be fully explained as the inverse process of absorption. By correctly accounting for contributions to the absorption from excitons and electron-hole continuum states, we are able to utilise the van Roosbroeck-Shockley relation to determine bimolecular recombination rate constants from absorption spectra.

We show that the sharpening of photon, electron and hole distribution functions significantly enhances bimolecular charge recombination as the temperature is lowered, mirroring trends in transient spectroscopy. Our findings provide vital understanding of band-to-band recombination processes in this hybrid perovskite, which comprise direct, fully radiative transitions between thermalized electrons and holes.

Lattice dynamics from phonon imaging.

Polaronic exciton binding energies calcd. Band gaps detd. IEEE J. Advances of optoelectronic devices based on methylammonium lead halide perovskites depend on understanding the role of excitons, whether it is marginal as in inorg. However, a consensus on the exciton binding energy and its temp. Here we det. In the temp. Implications of binding energy values on solar cell and LED workings are discussed. Photonics , 10 , 53 — 59 , DOI: Yang, Ye; Ostrowski, David P. We study the carrier dynamics in planar Me ammonium lead iodide perovskite films using broadband transient absorption spectroscopy.

We show that the sharp optical absorption onset is due to an exciton transition that is inhomogeneously broadened with a binding energy of 9 meV. We fully characterize the transient absorption spectrum by free-carrier-induced bleaching of the exciton transition, quasi-Fermi energy, carrier temp.

The photo-induced carrier temp.

We find an efficient hot-phonon bottleneck that slows down cooling of hot carriers by three to four orders of magnitude in time above a crit. Compared with mol. The electron-hole interaction is screened by a distance-dependent dielec. The energy spectrum and the eigenfunctions are calcd. The results show that the Pollmann-Buettner model, using the corresponding parameters obtained from ab initio calcns. The performance of lead-halide perovskites in optoelectronic devices is due to a unique combination of factors, including highly efficient generation, transport, and collection of photogenerated charge carriers.

The mechanism behind efficient charge generation in lead-halide perovskites is still largely unknown. Here, the authors investigate the factors that influence the exciton binding energy Eb in a series of metal-halide perovskites using accurate first-principles calcns.

They calc.

They then explore how different material combinations e. Intensity of Optical Absorption by Excitons. A band-theory exciton-effective-mass approximation examn. Milot, Rebecca L. The photoluminescence, transmittance, charge-carrier recombination dynamics, mobility, and diffusion length of CH3NH3PbI3 are investigated in the temp.


Profound changes in the optoelectronic properties of this prototypical photovoltaic material are obsd. Drude-like terahertz photocond.