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

Chemistry of Materials, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 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.

Language: Английский

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Machine learning accelerated nonadiabatic dynamics simulations of materials with excitonic effects

The Journal of Chemical Physics, Journal Year: 2025, Volume and Issue: 162(2)

Published: Jan. 8, 2025

This study presents an efficient methodology for simulating nonadiabatic dynamics of complex materials with excitonic effects by integrating machine learning (ML) models simplified Tamm–Dancoff approximation (sTDA) calculations. By leveraging ML models, we accurately predict ground-state wavefunctions using unconverged Kohn–Sham (KS) Hamiltonians. These ML-predicted KS Hamiltonians are then employed sTDA-based excited-state calculations (sTDA/ML). The results demonstrate that energies, time-derivative couplings, and absorption spectra from sTDA/ML accurate enough compared those conventional density functional theory based sTDA (sTDA/DFT) Furthermore, sTDA/ML-based molecular simulations on two different systems, namely chloro-substituted silicon quantum dot monolayer black phosphorus, achieve more than 100 times speedup the linear response time-dependent DFT simulations. work highlights potential ML-accelerated studying complicated photoinduced large offering significant computational savings without compromising accuracy.

Language: Английский

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Suppressing Polaronic Defect–Photocarrier Interaction in Halide Perovskites by Pre-distorting Its Lattice

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 8, 2025

In halide perovskites, photocarriers can have strong polaronic interactions with point defects. For iodide-deficient MAPbI3, we found that the Fermi level shift significantly by 0.6–0.7 eV upon light illumination. This energy is accompanied formation of deep electron traps. These experimental observations are consistent a Pb–Pb dimer when photoexcited electrons trapped at an iodide vacancy. Interestingly, this interaction suppressed portion MA+ cations replaced smaller Cs+ ions. Density functional theory calculations reveal Cs-doping reduce distance between two Pb atoms across vacancy, even without trapping. The predistortion lattice induced cation replacement resembles formed trapping defect site, which explains suppression light-induced effects observed in experiment. Our finding unveils counterintuitive strategy to enhance photostability perovskites preintroducing distortions into its lattice.

Language: Английский

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Luminescence From Localized States in Solids: A First‐Principles Perspective

Advanced Functional Materials, Journal Year: 2025, Volume and Issue: unknown

Published: March 3, 2025

Abstract Localized‐state luminescence (LSL) has emerged as a promising mechanism for high‐performance optoelectronic applications, including lighting, photodetection, and quantum technologies. Characterized by rich intriguing spectral features, LSL involves significant electron‐phonon coupling, which varies in strength across different systems. First‐principles methods, particularly density functional theory (DFT) its extensions provide an efficient framework modeling the process with reasonable accuracy. This comprehensive review examines DFT‐based studies on three representative types of solids: from self‐trapped excitons (STEs), normal defects, intentionally doped ions. The discussion begins overview entire process, highlighting computational methods excited state structures energies, well simulations luminescent spectrum within multi‐phonon transition framework. Detailed discussions follow, focusing structural distortion modes STEs, behavior mechanisms Finally, strategies to address current challenges advance theoretical design materials are proposed, offering valuable insights future developments field.

Language: Английский

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Self-passivation of Halide Interstitial Defects by Organic Cations in Hybrid Lead-Halide Perovskites: Ab Initio Quantum Dynamics

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(42), P. 29255 - 29265

Published: Oct. 11, 2024

Halide interstitial defects severely hinder the optoelectronic performance of metal halide perovskites, making research on their passivation crucial. We demonstrate, using ab initio nonadiabatic molecular dynamics simulations, that hydrogen vacancies (H

Language: 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, Journal Year: 2024, Volume and Issue: unknown, P. 12362 - 12369

Published: Dec. 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.

Language: Английский

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Interplay of Ultrafast Electron–Phonon and Electron–Electron Scattering in Ti₃C₂T_x MXenes: Ab Initio Quantum Dynamics

Nano Letters, Journal Year: 2025, Volume and Issue: unknown

Published: April 24, 2025

Nonthermal electrons are vital in solar energy and optoelectronics, yet their relaxation pathways not fully understood. Ab initio quantum dynamics reveal that Ti3C2O2 electron-phonon (e-ph) is faster than electron-electron (e-e) scattering due to strong coupling with the A1g phonon at 190 cm-1 presence of light C O atoms. Nuclear effects minimal; vibrations influence e-e only indirectly, mode' zero-point much lower thermal ambient conditions. Substituting heavier S Ti3C2OS slows e-ph enhances scattering, making it a process. However, both channels proceed concurrently, challenging time scale separation often used for metals. These results underscore need atomistic-level understanding nonthermal electron dynamics, especially light-element systems such as MXenes, provide guidance optimizing electronic advanced optoelectronic materials devices.

Language: Английский

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Atomistic Origin of Microsecond Carrier Lifetimes at Perovskite Grain Boundaries: Machine Learning-Assisted Nonadiabatic Molecular Dynamics

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 29, 2025

The polycrystalline nature of perovskites, stemming from their facile solution-based fabrication, leads to a high density grain boundaries (GBs) and point defects. However, the impact GBs on perovskite performance remains uncertain, with contradictory statements found in literature. We developed machine learning force field, sampled GB structures nanosecond time scale, performed nonadiabatic (NA) molecular dynamics simulations charge carrier trapping recombination stoichiometric doped GBs. reveal long, microsecond lifetimes, approaching experimental data, separation at small NA coupling, 0.01-0.1 meV. Stoichiometric exhibit transient trap states, which, however, are not particularly detrimental lifetime. Halide dopants form interstitial defects bulk, but have stabilizing influence structure by passivating undersaturated Pb atoms reducing state formation. On contrary, excess destabilizes GBs, allowing formation persistent midgap states that charges. Still, lifetime reduces relatively little, because decouple bands, charges more likely escape back into bands upon structural fluctuation. atomistic study its provides valuable insights complex properties perovskites intricate role material performance.

Language: Английский

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Advancing nonadiabatic molecular dynamics simulations in solids with E(3) equivariant deep neural hamiltonians

Nature Communications, Journal Year: 2025, Volume and Issue: 16(1)

Published: Feb. 27, 2025

Abstract Non-adiabatic molecular dynamics (NAMD) simulations have become an indispensable tool for investigating excited-state in solids. In this work, we propose a general framework, N 2 AMD (Neural-Network Non-Adiabatic Molecular Dynamics), which employs E(3)-equivariant deep neural Hamiltonian to boost the accuracy and efficiency of NAMD simulations. Distinct from conventional machine learning methods that predict key quantities NAMD, computes these directly with Hamiltonian, ensuring excellent accuracy, efficiency, consistency. not only achieves impressive performing at hybrid functional level within framework classical path approximation (CPA), but also demonstrates great potential predicting non-adiabatic coupling vectors suggests method go beyond CPA. Furthermore, generalizability enables seamless integration advanced techniques infrastructures. Taking several extensively investigated semiconductors as prototypical system, successfully simulate carrier recombination both pristine defective systems large scales where often significantly underestimates or even qualitatively incorrectly predicts lifetimes. This offers reliable efficient approach conducting accurate across various condensed materials.

Language: Английский

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Optimizing Excited Charge Dynamics in Layered Halide Perovskites through Compositional Engineering

Nano Letters, Journal Year: 2025, Volume and Issue: unknown

Published: March 19, 2025

Dion-Jacobson phase multilayered halide perovskites (MLHPs) improve carrier transport and optoelectronic performance thanks to their shorter interlayer distance, long lifetimes, minimized nonradiative losses. However, limited atomistic insights into dynamic structure-property relationships hinder rational design efforts further boost performance. Here, we employ nonadiabatic molecular dynamics, time-domain density functional theory, unsupervised machine learning uncover the impact of A-cation mixing on controlling excited dynamics recombination processes in MLHPs. Mixing smaller-sized Cs with methylammonium MLHP weakens electron-phonon interactions, suppresses losses, slows down intraband hot electron relaxations. On contrary, larger-sized guanidinium incorporation accelerates The mutual information analyses reveal importance distances, intra- interoctahedral angle motion extending lifetime by mitigating losses Our work provides a guideline for strategically choosing A-cations layered perovskites.

Language: Английский

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