How the Stacking Pattern Influences the Charge Transfer Dynamics of van der Waals Heterostructures: An Answer from a Time-Domain Ab Initio Study

Abstract

Here, we perform a time domain density functional study in conjunction with a non-adiabatic molecular dynamics (NAMD) simulation to investigate the charge carrier dynamics in a series of van der Waals heterostructures made of two-dimensional (2D) SnX 2 (X = S or Se)supported ZrS 2 , ZrSe 2 , and ZrSSe monolayers. Results from NAMD simulation reveal delayed electron−hole recombination (in the range of 0.53−2.13 ns) and ultrafast electron/hole transfer processes (electron transfer within 108.3−321.5 fs and hole transfer between 107.6 and 258.8 fs). The most interesting finding of our study is that switching from AB to AA stacking in the heterostructures extends the carrier lifespan by a significant amount. The delayed electron−hole recombination because of the switching stacking pattern can be rationalized by weak electron− phonon coupling, lower non-adiabatic coupling (NAC), and fast decoherence time. Thus, these insightful NAMD studies of excited charge carriers reveal that the stacking pattern variation is an effective tool to develop efficient photovoltaic devices based on 2D van der Waals heterostructures.

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

“…This method has been used successfully to model photo-excitation dynamics in a wide range of nanoscale and condensed-phase materials, including 3D perovskites with grain boundaries, point defects, dopants, and passivations, perovskites interacting with charge extraction layers, 2D Ruddelsden–Pooper (RP) and Dion–Jacobson (DJ) perovskites, 2D/3D heterostructures, TiO 2 bulk, and two-dimensional materials like black phosphorus, boron nitride, and others. 23,33–37 Earlier photo-induced charge dynamics experiments on 2D DJ perovskites, 2D RP perovskites with edge states and varying numbers of layers, and MAPbI 3 with grain boundaries and localized charges and interfaced with NiO, TiO 2 , and water yielded good findings. 11,33,34,38…”

“…15,53,54 Therefore, it is of the utmost importance to maintain the photogenerated electrons (e) and holes (h) at their places at the band edges for an extended period of time. 29,37,54–56 In order to accomplish this, it is essential that holes be concentrated at the VBM level of the heterostructure, and that electrons reach the CBM level as rapidly as is physically possible by losing as much energy as they have. 57…”

Hot Carrier Controlled Nitrogen Fixation Reaction in Metal-Free Boron-Anchored Aza-COF: Insight from Nonadiabatic Molecular Dynamics Simulation

“…The photocarrier dynamics was exploited by NAMD simulation as implemented in the Hefei-NAMD code, where the nonadiabatic couplings were estimated using the CA-nonadiabatic coupling (NAC) module . The free energy diagram in the NRR process was obtained based on the concept of the computational hydrogen electrode model developed by Norskov et al The details of NAMD simulations can be found elsewhere, , and the NRR calculations are available in Supporting Information.…”

Emergence of Z-Scheme Photocatalysis for Total Water Splitting: An Improvised Route to High Efficiency

“…2D stacked heterojunctions offer the highest degree of interface contact, facilitating interfacial charge transfer and separation, and thus, identifying suitable 2D materials for constructing g-C 3 N 4 -based Z-scheme photocatalytic systems with high performance is crucial. , Hexagonal boron nitride (h-BN) nanosheets, another metal-free 2D material structurally similar to graphene, have garnered extensive attention due to their excellent photocatalytic properties, including large surface area, high thermodynamic stability, and good thermal conductivity . However, as pointed out by Xu et al, the relatively large band gap of h-BN (4–6 eV) puts severe limitations on its photocatalytic applications under visible light response.…”

“…The two important parameters, namely, nonadiabatic coupling (NAC) and pure dephasing time, which one obtains from the NAMD simulation, practically determine the requisite time frame for photogenerated charge carrier separation, interfacial transfer, and carrier recombination. More precisely, NAC quantifies inelastic charge–phonon scattering, responsible for electron–phonon energy transfer, while the pure-dephasing time governs the coherence loss between the involved states of SC1 and SC2. ,, The average NAC matrix element ( d ij ) between two states i and j is defined by boldd italici italicj = ⟨ φ i true| ∂ ∂ t true| φ j ⟩ = false⟨ φ i | ∇ R Ĥ | φ j false⟩ ϵ j − ϵ i ( ∂ R ∂ t ) where Ĥ is the Kohn–Sham Hamiltonian, ε i / j is the energy of the electronic state φ i / j as a function of time, and ∂ bold-italicR ∂ t determines the nuclear velocity. In general, higher NAC values signify faster electron and hole relaxation times.…”