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Quantum dynamic simulation of triplet formation in an effective model of Y6 (BTP-4F)
Isabel Creed, Lucy J. F. Hart, Pranay Venkatesh +2
We construct a five-state model for photoexcitation in Y6 (BTP-4F) dimers, and then solve the non-adiabtic dynamics using the Hierarchical Equations of Motion (HEOM) method. We fin…
Six Open Questions in Machine-Learned Interatomic Potential Foundation Models
Isabel Creed, Tim Rein, Ingvars Vitenburgs +21
Machine-learned interatomic potentials (MLIPs) have had a profound impact on molecular modelling in recent years, promising to resolve the long-standing tension between the scale a…
Matching Terahertz and Hall Mobilities as a Hallmark of Intrinsic Charge Transport in Metal-Halide Perovskites
Dmitry R. Maslennikov, Ben P. Carwithen, Vladimir V. Bruevich +9
Charge-carrier transport in soft-lattice materials, including metal-halide perovskites, is often perceived to be highly heterogeneous across different length scales, and influenced…
Correcting hybrid density functionals to model Y6 and other non-fullerene acceptors
Tom Ward, Isabel Creed, Tim Rein +1
Recently developed fused-ring electron-acceptors such as Y6 (BTP-4F) have strong oscillator strength, good charge-carrier transport and a small bandgap. They therefore have enormou…
Anharmonic phonons with Gaussian processes
Keerati Keeratikarn, Jarvist Moore Frost
We provide a method for calculating anharmonic lattice dynamics, by building a surrogate model based on Gaussian Processes (GPs). Due to the underlying Gaussian form of a GP, the m…
Anisotropic electron-phonon interactions in 2D lead-halide perovskites
Jaco J. Geuchies, Johan Klarbring, Lucia Di Virgillio +8
Two-dimensional hybrid organic-inorganic metal halide perovskites offer enhanced stability for perovskite-based applications. Their crystal structure's soft and ionic nature gives…
Predicting polaron mobility in organic semiconductors with the Feynman variational approach
Bradley A. A. Martin, Jarvist Moore Frost
We extend the Feynman variational method applied to the parabolic-band Fröhlich (continuum) large polaron~\cite{Feynman1955} to a Holstein (lattice) small polaron, with a parabolic…
Multiple phonon modes in Feynman path-integral variational polaron mobility
Bradley A. A. Martin, Jarvist Moore Frost
The Feynman path-integral variational approach to the polaron problem\cite{Feynman1955}, along with the associated FHIP linear-response mobility theory\cite{Feynman1962}, provides…
Fröhlich polaron effective mass and localization length in cubic materials: degenerate and anisotropic electronic bands
Bogdan Guster, Pedro Melo, Bradley A. A. Martin +7
Polarons, that is, charge carriers correlated with lattice deformations, are ubiquitous quasiparticles in semiconductors, and play an important role in electrical conductivity. To…
Multi-Pulse Terahertz Spectroscopy Unveils Hot Polaron Photoconductivity Dynamics in Metal-Halide Perovskites
Xijia Zheng, Thomas R. Hopper, Andrei Gorodetsky +5
The behavior of hot carriers in metal-halide perovskites (MHPs) present a valuable foundation for understanding the details of carrier-phonon coupling in the materials as well as t…
Giant Huang-Rhys Factor for Electron Capture by the Iodine Interstitial in Perovskite Solar Cells
Lucy D. Whalley, Puck van Gerwen, Jarvist M. Frost +3
Improvement in the optoelectronic performance of halide perovskite semiconductors requires the identification and suppression of non-radiative carrier trapping processes. The iodin…
Accelerated hot-carrier cooling in MAPbI3 perovskite by pressure-induced lattice compression
Loreta A. Muscarella, Eline M. Hutter, Jarvist M. Frost +4
Hot-carrier cooling (HCC) in metal halide perovskites in the high-density regime is significantly slower compared to conventional semiconductors. This effect is commonly attributed…
Perspective: Dielectric and Ferroic Properties of Halide Perovskite Solar Cells
Jacob N. Wilson, Jarvist M. Frost, Suzanne K. Wallace +1
Halide perovskite semiconductors respond to electric fields in a way that varies across time and length scales. We discuss the microscopic processes that give rise to the macroscop…
Impact of non-parabolic electronic band structure on the optical and transport properties of photovoltaic materials
Lucy D. Whalley, Jarvist M. Frost, Benjamin J. Morgan +1
For semiconductors used in photovoltaic devices, the effective mass approximation allows calculation of important material properties from first-principles calculations, including…
Acoustic Phonon Lifetimes Limit Thermal Transport in Methylammonium Lead Iodide
Aryeh Gold-Parker, Peter M. Gehring, Jonathan M. Skelton +6
Hybrid organic-inorganic perovskites (HOIPs) have become an important class of semiconductors for solar cells and other optoelectronic applications. Electron-phonon coupling plays…
Dynamic Symmetry Breaking and Spin Splitting in Metal Halide Perovskites
Scott McKechnie, Jarvist M. Frost, Dimitar Pashov +3
Metal halide perovskites exhibit a materials physics that is distinct from traditional inorganic and organic semiconductors. While materials such as CH3NH3PbI3 are non-magnetic, th…
Spontaneous Octahedral Tilting in the Cubic Inorganic Caesium Halide Perovskites CsSnX and CsPbX (X = F, Cl, Br, I)
Ruo Xi Yang, Jonathan M. Skelton, E. Lora da Silva +2
The local crystal structures of many perovskite-structured materials deviate from the average space group symmetry. We demonstrate, from lattice-dynamics calculations based on quan…
Slow cooling of hot polarons in halide perovskite solar cells
Jarvist Moore Frost, Lucy D. Whalley, Aron Walsh
Halide perovskites show unusual thermalisation kinetics for above bandgap photo-excitation. We explain this as a consequence of excess energy being deposited into discrete large po…
Calculating polaron mobility in halide perovskites
Jarvist Moore Frost
Lead halide perovskite semiconductors are soft, polar, materials. The strong driving force for polaron formation (the dielectric electron-phonon coupling) is balanced by the light…
Perspective: Theory and simulation of hybrid halide perovskites
Lucy D. Whalley, Jarvist M. Frost, Young-Kwang Jung +1
Organic-inorganic halide perovskites present a number of challenges for first-principles atomistic materials modelling. These `plastic crystals' feature dynamic processes across mu…
A photon ratchet route to high-efficiency hybrid halide perovskite intermediate band solar cells
Jarvist M. Frost, Pooya Azarhoosh, Scott McKechnie +2
The spin-split indirect bandgap in hybrid-halide perovskites provides a momentum-space realisation of a photon-ratchet intermediate band. Excited electrons thermalise to recombinat…
Phonon anharmonicity, lifetimes and thermal transport in CHNHPbI from many-body perturbation theory
Lucy D. Whalley, Jonathan M. Skelton, Jarvist M. Frost +1
Lattice vibrations in CHNHPbI are strongly interacting, with double well instabilities present at the Brillouin zone boundary. Analysis within a first-principles lattic…
Indirect to direct bandgap transition in methylammonium lead halide perovskite
Tianyi Wang, Benjamin Daiber, Jarvist M. Frost +4
Methylammonium lead iodide perovskites are considered direct bandgap semiconductors. Here we show that in fact they present a weakly indirect bandgap 60 meV below the direct bandga…
Dynamic disorder, phonon lifetimes, and the assignment of modes to the vibrational spectra of methylammonium lead halide perovskites
Aurélien M. A. Leguy, Alejandro R. Goñi, Jarvist M. Frost +11
We present Raman and terahertz absorbance spectra of methylammonium lead halide single crystals (MAPbX3, X = I, Br, Cl) at temperatures between 80 and 370 K. These results show goo…