Photocatalytic activity of dual defect modified graphitic carbon nitride is robust to tautomerism: machine learning assisted ab initio quantum dynamics

Nanoscale, Год журнала: 2024, Номер 16(18), С. 8986 - 8995

Опубликована: Янв. 1, 2024

Transformations between multiple tautomeric forms of defective graphitic carbon nitride occur on nanosecond timescales, but these transformations have little influence charge carrier lifetimes.

Язык: Английский

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Sub-bandgap charge harvesting and energy up-conversion in metal halide perovskites: ab initio quantum dynamics

npj Computational Materials, Год журнала: 2025, Номер 11(1)

Опубликована: Янв. 11, 2025

Metal halide perovskites (MHPs) exhibit unusual properties and complex dynamics. By combining ab initio time-dependent density functional theory, nonadiabatic molecular dynamics machine learning, we advance quantum simulation to nanosecond timescale demonstrate that large fluctuations of MHP defect energy levels extend light absorption longer wavelengths enable trapped charges escape into bands. This allows low photons contribute photocurrent through up-conversion. Deep can become shallow transiently vice versa, altering the traditional classification deep. While fluctuate more in MHPs than semiconductors, some levels, e.g., Pb interstitials, remain far from band edges, acting as charge recombination centers. Still, many defects deemed detrimental based on static structures, are fact benign The extended harvesting up-conversion provide strategies for design novel solar, optoelectronic, information devices.

Язык: Английский

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Surface engineering for enhanced perovskite solar cells: Fullerene-mediated trap state formation on CsPbI3 (001) surface

Solar Energy Materials and Solar Cells, Год журнала: 2025, Номер 283, С. 113441 - 113441

Опубликована: Фев. 8, 2025

Язык: Английский

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Machine learning accelerated nonadiabatic dynamics simulations of materials with excitonic effects

The Journal of Chemical Physics, Год журнала: 2025, Номер 162(2)

Опубликована: Янв. 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.

Язык: Английский

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

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

Опубликована: Янв. 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.

Язык: Английский

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Point defect-mediated hot carrier relaxation dynamics of lead-free FASnI₃ perovskites

Nanoscale, Год журнала: 2024, Номер 16(9), С. 4737 - 4744

Опубликована: Янв. 1, 2024

In search of a promising optoelectronic performance, we herein investigated the hot carrier relaxation dynamics lead-free cubic phased bulk formamidinium tin triiodide (FASnI 3 ) perovskite.

Язык: Английский

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Enhanced Charge Separation in Single Atom Cobalt Based Graphitic Carbon Nitride: Time Domain Ab Initio Analysis

The Journal of Physical Chemistry Letters, Год журнала: 2024, Номер 15(8), С. 2202 - 2208

Опубликована: Фев. 19, 2024

In recent years, single atom catalysts have been at the forefront of energy conversion research, particularly in field catalysis. Carbon nitrides offer great potential as hosts for stabilizing metal atoms due to their unique electronic structure. We use ab initio nonadiabatic molecular dynamics study photoexcitation cobalt based graphitic carbon nitride. The results elucidate positive effect doped on structure GCN. Cobalt doping produces filled midgap states that serve oxidation centers, advantageous various redox reactions. presence enables harvesting longer wavelength photons, thereby extending absorption range solar light. Although accelerates charge relaxation overall, recombination is significantly slower than separation, creating beneficial conditions catalysis applications. simulations reveal detailed microscopic mechanism underlying improved performance system atomic defects and demonstrate an effective separation strategy construct highly efficient stable photocatalytic two-dimensional materials.

Язык: Английский

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Impact of Correlated Disorder on Surface Superconductivity: Revealing the Robustness of the Surface Ordering Effect

The Journal of Physical Chemistry Letters, Год журнала: 2024, Номер 15(9), С. 2573 - 2579

Опубликована: Фев. 28, 2024

Surface superconductivity, wherein electron pairing occurs at material surfaces or interfaces, has attracted a remarkable amount of attention since its discovery. Recent theoretical predictions have unveiled increased critical temperatures, especially the certain compounds and/or structures. The notion "surface ordering" been advanced to elucidate this phenomenon. Employing framework self-consistent Bogoliubov–de Gennes equations and model incorporating correlated disorder, our study demonstrates persistence surface ordering effect in presence weak moderate bulk disorder. Intriguingly, findings indicate that under disorder conditions temperature can be further increased, depending on intensity correlation

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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Surface Defects Control Bulk Carrier Densities in Polycrystalline Pb‐Halide Perovskites

Advanced Materials, Год журнала: 2024, Номер unknown

Опубликована: Окт. 31, 2024

Abstract The (opto)electronic behavior of semiconductors depends on their (quasi‐)free electronic carrier densities. These are regulated by semiconductor doping, i.e., controlled “electronic contamination”. For metal halide perovskites (HaPs), the functional materials in several device types, which already challenge some understanding properties, this study shows that doping type, density and properties derived from these, to a first approximation via surfaces. This effect, relevant all , found for some, is very evident lead (Pb)‐HaPs because intrinsically low electrically active bulk surface defect Volume densities most polycrystalline Pb‐HaP films (<1 µm grain diameter) below those resulting even < 0.1% sites being defects. implies consistent with interfacial defects controlling HaP devices multi‐layered structures action at two interfaces. Surface interface passivation effects electrical crucial developing used today. However, dopant introduction HaPs ppm levels electronic‐relevant so difficult, vastly more critical dominate, approximation, optoelectronic characteristics devices.

Язык: Английский

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