Halide Vacancies Create No Charge Traps on Lead Halide Perovskite Surfaces but Can Generate Deep Traps in the Bulk

The Journal of Physical Chemistry Letters, Год журнала: 2023, Номер 14(26), С. 6028 - 6036

Опубликована: Июнь 23, 2023

Metal halide perovskites (MHPs) have attracted attention because of their high optoelectronic performance that is fundamentally rooted in the unusual properties MHP defects. By developing an ab initio-based machine-learning force field, we sample structural dynamics MHPs on a nanosecond time scale and show vacancies create midgap trap states bulk but not surface. Deep traps result from Pb-Pb dimers can form across vacancy only bulk. The required shortening distance by nearly 3 Å facilitated either charge trapping or 50 ps thermal fluctuations. large-scale deformations are possible soft. Halide surface no deep separate electrons holes, keeping charges mobile. This particularly favorable for quantum dots, which do require sophisticated passivation to emit light blink less than dots formed traditional inorganic semiconductors.

Язык: Английский

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Compression Eliminates Charge Traps by Stabilizing Perovskite Grain Boundary Structures: An Ab Initio Analysis with Machine Learning Force Field

Chemistry of Materials, Год журнала: 2024, Номер 36(6), С. 2898 - 2906

Опубликована: Март 12, 2024

Grain boundaries (GBs) play an important role in determining the optoelectronic properties of perovskites, requiring atomistic understanding underlying mechanisms. Strain engineering has recently been employed perovskite solar cells, providing a novel perspective on GBs. Here, we theoretically investigate impact axial strain geometric and electronic common CsPbBr3 GB. We develop machine learning force field perform ab initio calculations to analyze behavior GB models with different strains nanosecond time scale. Our results demonstrate that compressing efficiently suppresses structural fluctuations eliminates trap states originating from large-scale distortions. The becomes more amorphous under compressive strain, which makes relationship between structure nonmonotonic. These can help clarify conflicts experiments.

Язык: Английский

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Band Gap Narrowing in Lead-Halide Perovskites by Dynamic Defect Self-Doping for Enhanced Light Absorption and Energy Upconversion

Chemistry of Materials, Год журнала: 2025, Номер unknown

Опубликована: Янв. 6, 2025

Metal halide perovskites (MHP) have attracted great attention in the photovoltaic industry due to their high and rapidly rising power conversion efficiencies, currently over 25%. However, hybrid organic-inorganic MHPs are inherently chemically unstable, limiting application. All-inorganic perovskites, such as CsPbI3, many merits, but stable efficiency is lower, around 18%, a larger band gap causing mismatch with solar spectrum. Choosing α-CsPbI3 prototypical system, we demonstrate new general concept of dynamic defects that fluctuate between deep shallow states, increase range absorbed photons, without accelerating nonradiative electron-hole recombination. In deeper energy state, narrow allow harvesting light longer wavelengths. Fluctuating shallower energies, escape photogenerated charges into bands, enabling charge transport resulting defect-mediated upconversion thermal electricity. Defect covalency participation low-frequency anharmonic vibrations decouple trapped from free carriers, minimizing carrier losses. Our findings defect dynamics unique important properties MHPs, can be used optimize for efficient optoelectronic applications.

Язык: Английский

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Nuclear Quantum Effects Accelerate Hot Carrier Relaxation but Slow Down Recombination in Metal Halide Perovskites

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Март 19, 2025

Inorganic semiconductors are composed of heavy elements whose vibrational motions well described by classical mechanics. Heavy elements, such as Pb and I, support charge carriers in metal halide perovskites. Nevertheless, the soft structure strong coupling between organic inorganic components create conditions which nuclear quantum effects (NQEs) can play important roles. By combining ab initio, ring-polymer, nonadiabatic molecular dynamics approaches with time-domain density functional theory, we demonstrate how NQEs influence structural electronic properties electron-vibrational hybrid organic-inorganic (MAPbI3) all-inorganic (CsPbI3) Quantum zero-point fluctuations enhance disorder, reduce band gap, accelerate elastic scattering responsible for coherence loss. have opposite influences on intraband carrier relaxation interband recombination. These inelastic events governed product overlap-like electron-phonon matrix element atomic velocity. overlap increases The involves many states. Reduction some states is offset other pathways, while an increased velocity makes faster. Electron-hole band-edge plays a key role recombination, its reduction NQEs-enhanced disorder recombination slower. This phenomenon seen both MAPbI3 CsPbI3 much more pronounced when light component present. study offers detailed understanding processes perovskites, offering theoretical insights into hot that govern performance solar cells optoelectronic devices.

Язык: Английский

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Decoherence ensures convergence of non-adiabatic molecular dynamics with number of states

The Journal of Chemical Physics, Год журнала: 2024, Номер 161(6)

Опубликована: Авг. 9, 2024

Non-adiabatic (NA) molecular dynamics (MD) is a powerful approach for studying far-from-equilibrium quantum in photophysical and photochemical systems. Most NA-MD methods are developed tested with few-state models, their validity complex systems involving many states not well studied. By modeling intraband equilibration interband recombination of charge carriers MoS2, we investigate the convergence three popular algorithms, fewest switches surface hopping (FSSH), global flux (GFSH), decoherence induced (DISH) number states. Only standard DISH algorithm converges produces Boltzmann equilibrium. Unitary propagation wave function FSSH GFSH violates distribution, leads to internal inconsistency between time-dependent Schrödinger equation state populations trajectory counts, non-convergent results. Introducing by collapsing fixes these problems. The simplified version that omits projecting out occupied applicable also causes problems when increased. We discuss algorithmic application collapse detailed balance provide FSSH, GFSH, flow charts. use convergent highly important complicated processes multiple Our findings basis investigating realistic

Язык: Английский

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Spin–Orbit Coupling Notably Retards Non-radiative Electron–Hole Recombination in Methylammonium Lead Triiodide Perovskites

The Journal of Physical Chemistry Letters, Год журнала: 2023, Номер 14(11), С. 2715 - 2721

Опубликована: Март 9, 2023

The giant spin–orbit coupling (SOC) of a heavy lead element significantly extends charge carrier lifetimes halide perovskites (LHPs). physical mechanism remains unclear and requires quantum dynamics perspective. Taking methylammonium iodide (MAPbI3) as prototypical system using non-adiabatic molecular combined with 1/2 electron correction, we show that SOC notably reduces the non-radiative electron–hole (e–h) recombination by decreasing (NAC) primarily result e–h wave function overlap reshaping hole functions. Second, causes spin mismatch subject to spin-mixed states, which further decreases NAC. lifetime is about 3-fold longer in present relative absence SOC. Our study generates fundamental understanding minimizing energy losses LHPs.

Язык: Английский

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Ion Migration at Metal Halide Perovskite Grain Boundaries Elucidated with a Machine Learning Force Field

The Journal of Physical Chemistry Letters, Год журнала: 2024, Номер unknown, С. 12362 - 12369

Опубликована: Дек. 9, 2024

Metal halide perovskites are promising optoelectronic materials with excellent defect tolerance in carrier recombination, believed to arise largely from their unique soft lattices. However, weak lattice interactions also promote ion migration, leading serious stability issues. Grain boundaries (GBs) have been experimentally identified as the primary migration channels, but relevant mechanism remains elusive. Using molecular dynamics a machine learning force field, we directly model at common CsPbBr3 GB. We demonstrate that as-built GB model, containing 6400 atoms, experiences structural reconstruction over several nanoseconds, and only Br atoms diffuse after that. A fraction of near either migrate toward center or along through different channels. Increasing temperature not accelerates via Arrhenius activation allows more migrate. The energies much lower than bulk due large-scale distortions favorable non-stoichiometric local environments available GBs. Making composition stoichiometric by doping annealing can suppress migration. reported results provide valuable atomistic insights into properties metal perovskites.

Язык: Английский

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An appraisal of the role of lanthanide doping in stabilization and performance improvement of [Sm3+-Eu3+-Tm3+]:CsPbI2.2Br0.8 for high-performance energy systems

Electrochimica Acta, Год журнала: 2024, Номер 487, С. 144186 - 144186

Опубликована: Март 28, 2024

Язык: Английский

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Controlling Charge Carrier Dynamics in Porphyrin Nanorings by Optically Active Templates

The Journal of Physical Chemistry Letters, Год журнала: 2023, Номер 14(50), С. 11384 - 11392

Опубликована: Дек. 11, 2023

Understanding the dynamics of photogenerated charge carriers is essential for enhancing performance solar and optoelectronic devices. Using atomistic quantum simulations, we demonstrate that a short π-conjugated optically active template can be used to control hot carrier relaxation, separation, recombination in light-harvesting porphyrin nanorings. Relaxation holes slowed by 60% with an compared analogous inactive template. Both systems exhibit subpicosecond electron transfer from photoactive core templates. Notably, suppressed 6-fold The time-domain simulations rationalize these effects extent hole localization, modification density states, participation distinct vibrational motions, changes coherence. Extension lifetime reduction recombination, without hampering strategy efficiencies energy materials

Язык: Английский

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The Impact of Short-Range (Gaussian) Disorder Correlations on Superconducting Characteristics

Condensed Matter, Год журнала: 2024, Номер 9(1), С. 6 - 6

Опубликована: Янв. 12, 2024

The pursuit of enhanced superconducting device performance has historically focused on minimizing disorder in materials. Recent research, however, challenges this conventional wisdom by exploring the unique characteristics disordered Following studies, is currently viewed as a design parameter that can be tuned. This shift paradigm sparked an upsurge research efforts, which demonstrates significantly augment superconductivity figures merit. While almost all previous studies attended to effects related strength, article focuses impact short-range correlations real materials takes place, for example, due lattice defects. study shows degree such strongly influence characteristics.

Язык: Английский

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