Tuning the Carrier Lifetime in Black Phosphorene through Family Atom Doping

Characteristics and performance of layered two-dimensional materials under doping engineering

In recent years, doping engineering, which is widely studied in theoretical and experimental research, is an effective means to regulate the crystal structure and physical properties of two-dimensional materials and expand their application potential. Based on different types of element dopings, different 2D materials show different properties and applications. In this paper, the characteristics and performance of rich layered 2D materials under different types of doped elements are comprehensively reviewed. Firstly, 2D materials are classified according to their crystal structures. Secondly, conventional experimental methods of charge doping and heterogeneous atom substitution doping are summarized. Finally, on the basis of various theoretical research results, the properties of several typical 2D material representatives under charge doping and different kinds of atom substitution doping as well as the inspiration and expansion of doping systems for the development of related fields are discussed. Through this review, researchers can fully understand and grasp the regulation rules of different doping engineering on the properties of layered 2D materials with different crystal structures. It provides theoretical guidance for further improving and optimizing the physical properties of 2D materials, improving and enriching the relevant experimental research and device application development.

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

In search of a promising optoelectronic performance, we herein investigated the hot carrier relaxation dynamics of a lead-free cubic phased bulk formamidinium tin triiodide (FASnI3) perovskite. To gain detailed theoretical insights, we should estimate the carrier relaxation dynamics of this pristine perovskite. To control the dynamics, point defects like central tin (Sn), iodine(I) anions, and formamidinium (FA) cations were introduced. With the iodine vacancy in the FASnI3 perovskite, the system seems to be unstable at room temperature, whereas the other three types of FASnI3 perovskites (pristine, Sn vacancy, and FA vacancy) are significantly stable at 300 K having semiconducting nature and excellent optical absorption in the UV-visible range. The computed electron-hole recombination time for the pristine system is 3.9 nanoseconds, which is in good agreement with the experimental investigation. The exciton relaxation processes in Sn and FA vacancy perovskites require 2.8 and 4.8 nanoseconds, respectively. These variations in the hot carrier relaxation dynamics processes are caused by the generation of significant changes in non-adiabatic coupling between energy levels, electron-phonon coupling, and quantum decoherence in different point defect analogous systems. The results presented here offer deeper insight into the temperature-dependent carrier relaxation dynamics of FASnI3 perovskites and thus open up opportunities for future exploration of their optoelectronic properties.

Efficient photoreduction of carbon dioxide to ethanol using diatomic nitrogen-doped black phosphorus

Successful conversion of CO2 into C2 products requires the development of new catalysts that overcome the difficulties in efficient light harvesting and CO-CO coupling. Herein, density functional theory (DFT) is used to assess the photoreduction properties of nitrogen-doped black phosphorus. The geometric structure, redox potential, first step of hydrogenation activation, CO desorption, and CO-CO coupling are systematically calculated, based on which the diatomic nitrogen-doped black phosphorus (N2@BPV) stands out. The calculated results of the CO2RR pathway demonstrate that N2@BPV has excellent selectivity and high activity for CH3CH2OH production. The results of the time-dependent ab initio nonadiabatic molecular dynamics simulation show that the diatomic N active sites of N2@BPV facilitate charge separation and inhibit electron-hole recombination. In addition, the activation mechanism of CO2 is studied. The main reason for CO2 activation is attributed to the imbalance in electron transfer that destroys the symmetry of CO2. We expect that our study will offer some theoretical guidance in CO2 conversion.

Mechanism of p-Type Heteroatom Doping of Lithium Stannate for the Photodegradation of 2,4-Dichlorophenol: Enhanced Hole Oxidative Capability and Concentrations

A systematic evaluation of enhancing photocatalysis via aliovalent cation doping is conducted. Cation In3+, being p-type-doped, was chosen to substitute the Sn site (Sn4+) in Li2SnO3, and the photodegradation of 2,4-dichlorophenol was applied as a model reaction. Specifically, Li2Sn0.90In0.10O3 exhibited superior catalytic performance; the photodegradation efficiency reached about 100% within only 12 min. This efficiency is far greater than that of pure Li2SnO3 under identical conditions. Density functional theory calculations reveal that introducing In3+ increased the electron mobility, yet decreased the hole mobility, leading to photogenerated carrier separation. However, photoluminescence and time-resolved photoluminescence suggest that In3+ induced nonradiative coupling in the matrix, reducing the photogenerated carrier separation ratio compared with that of Li2SnO3. The optical band gap of Li2Sn0.90In0.10O3 was almost unchanged compared with that of Li2SnO3 via ultraviolet-visible absorption. The increased photocatalytic efficiency was ascribed to the lower valence band position and enhanced hole concentrations by valence band X-ray photoelectron spectroscopy and electrochemical measurements. Finally, a 2,4-dichlorophenol degradation pathway, an intermediate toxicity assessment, and a photocatalytic mechanism were proposed. This work offers insights into designing and optimizing semiconductor photocatalysts with high performance.

Blocking recombination centers by controlling the charge density of a sulfur vacancy in antimony trisulfide

By performing nonadiabatic molecular dynamics combined with ab initio time-domain density functional theory, we have explored the effects of the charge density of a sulfur vacancy on charge trapping and recombination in antimony trisulfide (Sb2S3). The simulations demonstrate that, compared to an antimony vacancy, the sulfur vacancy generates a high charge density trap state within the band gap. This state acts as the recombination center and provides new channels for charge carrier relaxation. Filling the sulfur vacancy with electron donors elevates the defect state to the Fermi level due to the introduced extra electrons. In contrast, the electron acceptor lowers the charge density of the sulfur vacancy by capturing its local electrons, eliminating the charge recombination center and extending the photo-generated charge carrier lifetime. Additionally, compared with electron injection, hole injection can also decrease the charge density of the trap state via neutralizing its local electronic states, eliminate the trap state within the band gap, and suppress nonradiative electron-hole recombination. This study is expected to shed new light on the blocking recombination centers and provide valuable insights into the design of high-performance solar cells.

High-performance and self-powered photodetectors from an S-scheme Cs2SnI2Cl2/Cs2TiI6 heterojunction: a DFT+NAMD study

The recently reported two-dimensional (2D) Ruddlesden-Popper perovskite materials exhibit a plethora of advantages, making them an ideal candidate for constructing high-performance photodetectors. The mixed 2D/3D Cs2SnI2Cl2/Cs2TiI6 heterojunction is an S-scheme heterojunction and has excellent light trapping ability. Due to the spontaneous transfer of carriers caused by different work functions, a built-in electric field is formed in the heterojunction and the self-powered capability is provided. Through the nonadiabatic molecular dynamics (NAMD) method, it is found that the heterojunction exhibits fast photoresponse, low losses and efficient carrier separation. In addition, biaxial compressive strain can not only broaden the photoresponse of the Cs2SnI2Cl2/Cs2TiI6 heterojunction in the near-infrared region and enhance the optical absorption coefficient of the heterojunction, but also enhance the self-powered ability of the heterojunction. Our discoveries present a highly effective avenue for the future development of high-performance, self-powered hybrid optoelectronic devices.

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

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) SnX2 (X = S or Se)-supported ZrS2, ZrSe2, 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.

Pseudo-heterostructure and condensation of 1D moiré excitons in twisted phosphorene bilayers

Heterostructures are not expected to form in a single homogeneous material. Here, we show that planar pseudo-heterostructures could emerge in a twisted bilayer of phosphorene (tbP), driving in-plane energy and charge transfer. The formation of moiré superlattices combined with electronic anisotropy in tbPs yields one-dimensional (1D) moiré excitons with long radiative and nonradiative lifetimes, large binding energies, and deep moiré potentials. Low-frequency moiré phonons and dynamic moiré potentials are revealed to be responsible for the in-plane energy/charge transfer and exciton dynamics. The 1D moiré excitons are predicted to exhibit Bose-Einstein condensation at high temperatures and may lead to exotic Tonks-Girardeau Bose gases.

Suppressing Nonradiative Recombination by Electron-Donating Substituents in 2D Conjugated Triphenylamine Polymers toward Efficient Perovskite Optoelectronics

Highly efficient perovskite optoelectronics (POEs) have been limited by nonradiative recombination. We report a strategy to inhibit the nonradiative recombination of 2D triphenylamine polymers in the hole transport layer (HTL) via introducing electron-donating groups to enhance the conjugation effect and electron cloud density. The conjugated systems with electron-donating groups present smaller energy level oscillation compared to the ones with electron-absorbing groups, as confirmed by nonadiabatic molecular dynamics (NAMD) calculation. Further study reveals that the introduction of low-frequency phonons in the electron-donating group systems shortens the nonadiabatic coupling and inhibits the nonradiative recombination. Such electron-donating groups can decrease the valence band maximum of 2D polymers and promote hole transport. Our report provides a new design strategy to suppress nonradiative recombination in HTL for application in efficient POEs.

Insights into Photoinduced Carrier Dynamics and Overall Water Splitting of Z-Scheme van der Waals Heterostructures with Intrinsic Electric Polarization

Using first-principles calculations in combination with nonadiabatic molecular dynamics (NAMD), we propose novel heterostructures of carbon nitride (C₇N₆) and the Janus GaSnPS monolayer as promising direct Z-scheme photocatalysts for solar-driven overall water splitting. The out-of-plane electric field due to the electric polarization which is dependent on the stacking pattern alters the band alignment and catalytic activity of the heterostructures. The relatively strong interfacial nonadiabatic coupling and long quantum coherence time accelerate the interlayer carrier recombination, enabling a direct Z-scheme photocatalytic mechanism. More importantly, the redox ability of the remanent photogenerated carriers in the Z scheme is strong enough to trigger both the hydrogen evolution reaction (HER) and oxygen reduction reaction (OER) simultaneously without the help of sacrificial agents. Our work reveals a fundamental understanding of ultrafast charge carrier dynamics at vdW heterointerfaces as well as new design prospects for highly efficient direct Z-scheme photocatalysts.

Interlayer Doping of Cu on Bilayer Black Phosphorus for Enhanced Charge Transfer and Transport Properties

Metal doping between black phosphorus (BP) layers has great advantages in modulating electronic properties. Here, the effects of Cu intercalation on charge transfer and carrier dynamics are investigated by theoretical calculations. Relative to the pristine bilayer BP, Cu suppresses the nonradiative electron-hole recombination, reducing the major pathways of energy and current loss. Furthermore, we investigate a novel pn homogeneous junction based on the Cu-doped bilayer BP, which shows enhanced transport properties and Ohmic contact characteristics. This is because doping leads to the transformation of BP from p-type to n-type, charge accumulation on conduction bands allows electrons to be easily transferred to the p-type bilayer BP, and associated electrical properties can be modulated by the doping concentration. This study has fundamental importance for understanding structure-property relationships in metal intercalation, which is an important guidance for integration and interlayer engineering for two-dimensional materials.

Vacancy-Regulated Charge Carrier Dynamics and Suppressed Nonradiative Recombination in Two-Dimensional ReX2 (X = S, Se)

Point defects in semiconductors usually act as nonradiative charge carrier recombination centers, which severely limit the performance of optoelectronic devices. In this work, by combining time-domain density functional theory with nonadiabatic molecular dynamics simulations, we demonstrate suppressed nonradiative charge carrier recombination and prolonged carrier lifetime in two-dimensional (2D) ReX₂ (X = S, Se) with S/Se vacancies. In particular, a S vacancy introduces a shallow hole trap state in ReS₂, while a Se vacancy introduces both hole and electron trap states in ReSe₂. Photoexcited electrons and holes can be rapidly captured by these defect states, while the release process is slow, which contributes to an elongated photocarrier lifetime. The suppressed charge carrier recombination lies in the vacancy-induced low-frequency phonon modes that weaken electron-phonon coupling, as well as the reduced overlap between electron and hole wave functions that decreases nonadiabatic coupling. This work provides physical insights into the charge carrier dynamics of 2D ReX₂, which may stimulate considerable interest in using defect engineering for future optoelectronic nanodevices.

Ultrafast Charge Transfer and Delayed Recombination in Graphitic-CN/WTe2 van der Waals Heterostructure: A Time Domain Ab Initio Study

In search of an efficient solar energy harvester, we herein performed a time domain density functional study coupled with nonadiabatic molecular dynamics (NAMD) simulation to gain atomistic insight into the charge carrier dynamics of a graphitic carbon nitride (g-CN)-tungsten telluride (WTe₂) van der Waals heterostructure. Our NAMD study predicted ultrafast electron (589 fs) and hole-transfer (807 fs) dynamics in g-CN/WTe₂ heterostructure and a delayed electron-hole recombination process (2.404 ns) as compared to that of the individual g-CN (3 ps) and WTe₂ (0.55 ps) monolayer. The ultrafast charge transfer is due to strong electron-phonon coupling during the charge-transfer process while comparatively weak electron-phonon coupling, sufficient band gap, comparatively lower nonadiabatic coupling (NAC), and fast decoherence time slow down the electron-hole recombination process. The NAMD results of exciton relaxation dynamics are valuable for insightful understanding of charge carrier dynamics and in designing photovoltaic devices based on organic-inorganic 2D van der Waals heterostructures.

Two Dimensional MOene: From Superconductors to Direct Semiconductors and Weyl Fermions

The number of semiconducting MXenes with direct band gaps is extremely low; thus, it is highly desirable to broaden the MXene family beyond carbides and nitrides to expand the palette of desired chemical and physical properties. Here, we theoretically report the existence of the single-layer (SL) dititanium oxide 2H-Ti₂O MOene (MXene-like 2D transition oxides), showing an Ising superconducting feature. Moreover, SL halogenated 2H- and 1T-Ti₂O monolayers display tunable semiconducting features and strong light-harvesting ability. In addition, the external strains can induce Weyl fermions via quantum phase transition in 2H-Ti₂OF₂ and Ti₂OCl₂ monolayers. Specifically, 2H- and 1T-Ti₂OF₂ are direct semiconductors with band gaps of 0.82 and 1.18 eV, respectively. Furthermore, the carrier lifetimes of SL 2H- and 1T-Ti₂OF₂ are evaluated to be 0.39 and 2.8 ns, respectively. This study extends emerging phenomena in a rich family of 2D MXene-like MOene materials, which provides a novel platform for next-generation optoelectronic and photovoltaic fields.

Engineering van der Waals Materials for Advanced Metaphotonics

The outstanding chemical and physical properties of 2D materials, together with their atomically thin nature, make them ideal candidates for metaphotonic device integration and construction, which requires deep subwavelength light-matter interaction to achieve optical functionalities beyond conventional optical phenomena observed in naturally available materials. In addition to their intrinsic properties, the possibility to further manipulate the properties of 2D materials via chemical or physical engineering dramatically enhances their capability, evoking new science on light-matter interaction, leading to leaped performance of existing functional devices and giving birth to new metaphotonic devices that were unattainable previously. Comprehensive understanding of the intrinsic properties of 2D materials, approaches and capabilities for chemical and physical engineering methods, the resulting property modifications and novel functionalities, and applications of metaphotonic devices are provided in this review. Through reviewing the detailed progress in each aspect and the state-of-the-art achievement, insightful analyses of the outstanding challenges and future directions are elucidated in this cross-disciplinary comprehensive review with the aim to provide an overall development picture in the field of 2D material metaphotonics and promote rapid progress in this fast emerging and prosperous field.

Strain modulation of the exciton anisotropy and carrier lifetime in black phosphorene

Manipulating excitons is of great significance to explore the optical properties of 2D materials. In this work, we investigate the excitonic properties and carrier dynamics of bilayer black phosphorene by imposing in-plane biaxial strain. The results show that the strain can modulate not only the contribution of the excitons to optical absorption but also the anisotropic shape of the first exciton. This can be ascribed to the strain effect on the band realignment as well as to changes of the parity and the electron effective mass at the CBM. At the temperature of 300 K, a 3% strain reduces the non-adiabatic coupling between the VBM and CBM and then increases the carrier lifetime by a factor of 13, and the results can be used to estimate the strain effect on the excitonic lifetime. Our results demonstrate that manipulation of the biaxial strain is a promising strategy to modulate the exciton properties of black phosphorene.

Excited state dynamics in monolayer black phosphorus revisited: Accounting for many-body effects

The dynamics of electron-hole recombination in pristine and defect-containing monolayer black phosphorus (ML-BP) has been studied computationally by several groups relying on the one-particle description of electronic excited states. Our recent developments enabled a more sophisticated and accurate treatment of excited states dynamics in systems with pronounced excitonic effects, including 2D materials such as ML-BP. In this work, I present a comprehensive characterization of optoelectronic properties and nonadiabatic dynamics of the ground state recovery in pristine and divacancy-containing ML-BP, relying on the linear-response time-dependent density functional theory description of excited states combined with several trajectory surface hopping methodologies and decoherence correction schemes. This work presents a revision and new implementation of the decoherence-induced surface hopping methodology. Several popular algorithms for nonadiabatic dynamics algorithms are assessed. The kinetics of nonradiative relaxation of lower-lying excited states in ML-BP systems is revised considering the new methodological developments. A general mechanism that explains the sensitivity of the nonradiative dynamics to the presence of divacancy defect in ML-BP is proposed. According to this mechanism, the excited states' relaxation may be inhibited by the presence of energetically close higher-energy states if electronic decoherence is present in the system.

Computational study of therapeutic potential of phosphorene as a nano-carrier for drug delivery of nebivolol for the prohibition of cardiovascular diseases: a DFT study

Density functional theory (DFT) calculations were utilized to assess the drug delivery efficiency of phosphorene carrier for nebivolol drug to treat cardiovascular diseases. The optimized structures, excited state, and electronic properties of nebivolol, phosphorene, and nebivolol-phosphorene (nebivolol-PH) complex were considered to determine the drug delivery ability of phosphorene at the target site. The increased dipole moment (6.08 D) results in the higher solubility of the complex in polar solvents (water). Weak interactive forces between nebivolol and phosphorene were demonstrated by the non-covalent interaction (NCI) plot that facilitated the offloading of nebivolol at the targeted area. The analysis of frontier molecular orbitals (FMOs) revealed that during excitation, the charge was transferred from nebivolol as a higher occupied molecular orbital (HOMO) to phosphorene as a lower unoccupied molecular orbital (LUMO). Thus, the charge-transfer process was further studied by charge decomposition analysis (CDA). The calculated results at the excited state for the nebivolol-PH complex exhibited that the maximum wavelength (λmax) was red-shifted by 6 nm in the gas phase. The electron-hole theory and photoinduced electron transfer (PET) processes were carried out for the exploration of different excited states of the complex. Additionally, phosphorene with + 1 and - 1 charge states indicated the minor structural changes and provide the stable nebivolol-PH complex. This theoretical study also investigated that phosphorene can be exploited as an effective carrier for the delivery of a therapeutic agent as nebivolol to treat cardiovascular diseases. This work will also encourage the researchers to investigate the other 2D nanoparticles as a nano-drug delivery system (NDDS).

Strong Modulation of Band Gap, Carrier Mobility and Lifetime in Two-Dimensional Black Phosphorene through Acoustic Phonon Excitation

Black phosphorene (BP) has been attracting intense attention due to its high charge mobility and potential applications in electronic, optical and optoelectronic devices. We demonstrate by ab initio molecular dynamics and nonadiabatic quantum dynamics simulations that the excitation of out-of-plane acoustic phonon (ZA) provides strong modulation of the band gap, carrier lifetime and carrier mobility in BP. A 1% tensile strain can significantly enhance ZA mode excitation at room temperature, distinctly reducing the band gap, carrier mobility, and lifetime. These electronic properties can be tuned easily by influencing the excitation amplitude of the ZA mode. Unique to the family of two-dimensional materials, the ZA mode plays an essential role in controlling the electronic properties of BP. The results of our study provide valuable guidelines for design of functional nanodevices based on 2D BP.

Concentric Approximation for Fast and Accurate Numerical Evaluation of Nonadiabatic Coupling with Projector Augmented-Wave Pseudopotentials

We develop an efficient and accurate method for numerical evaluation of nonadiabatic (NA) coupling in the Kohn-Sham representation with projector augmented-wave (PAW) pseudopotentials that are commonly used in electronic structure calculations on nanoscale, condensed matter, and molecular systems. Without additional cost, the method provides an order of magnitude improvement in accuracy compared to the current technique, while it is 3-4 orders of magnitude faster than the exact evaluation. Atomic displacements over typical time steps in molecular dynamics (MD) simulations are much smaller than the size of the PAW core region, and therefore, evaluation of the NA in the core is simplified. The accuracy is demonstrated with three condensed matter systems. The method is robust to variation in the MD time step. The accurate NA coupling evaluation also helps in maintaining phase-consistency of the NA coupling and identifying trivial crossings of adiabatic states. The approach stimulates NAMD applications to modeling of modern materials and processes.

Time-Domain Ab Initio Insights into the Reduced Nonradiative Electron-Hole Recombination in ReSe2/MoS2 van der Waals Heterostructure

Two-dimensional (2D) ReSe₂ has attracted considerable interest due to its unique anisotropic mechanical, optical, and exitonic characteristics. Recent transient absorption experiments demonstrated a prolonged lifetime of photoexcited charge carriers by stacking ReSe₂ with MoS₂, but the underlying mechanism remains elusive. Here, by combining time-domain density functional theory with nonadiabatic molecular dynamics, we investigate the electronic properties and charge carrier dynamics of 2D ReSe₂/MoS₂ van der Waals (vdW) heterostructure. ReSe₂/MoS₂ has a type II band alignment that exhibits spatially distinguished conduction and valence band edges, and a built-in electric field is formed due to interface charge transfer. Remarkably, in spite of the decreased band gap and increased decoherence time, we demonstrate that the photocarrier lifetime of ReSe₂/MoS₂ is ∼5 times longer than that of ReSe₂, which originates from the greatly reduced nonadiabatic coupling that suppresses electron-hole recombination, perfectly explaining the experimental results. These findings not only provide physical insights into experiments but also shed light on future design and fabrication of functional optoelectronic devices based on 2D vdW heterostructures.

A Simple Solution to Trivial Crossings: A Stochastic State Tracking Approach

We present a new state tracking algorithm based on a stochastic state reassignment that reflects the quantum mechanical interpretation of the state time-overlaps. We assess the new method with a range of model Hamiltonians and demonstrate that it yields the results generally consistent with the deterministic min-cost algorithm. However, the stochastic state tracking algorithm reduces magnitudes of the state population fluctuations as the quantum system evolves toward its equilibrium. The new algorithm facilitates the thermalization of quantum state populations and suppresses the population revivals and oscillations near the equilibrium in many-state systems. The new stochastic algorithm has a favorable computational scaling, is easy to implement due to its conceptual transparency, and treats various types of state identity changes (trivial or avoided crossings and any intermediate cases) on equal footing.

Accurate Computation of Nonadiabatic Coupling with Projector Augmented-Wave Pseudopotentials

Synergy of nonadiabatic molecular dynamics with real-time time-dependent density functional theory has led to significant progress in modeling excited-state dynamics in nanoscale and condensed matter systems over the past decade. Nonadiabatic coupling (NAC) is the central quantity in such simulations, and its accurate and efficient evaluation is an enduring challenge in time-dependent Kohn-Sham theory, particularly in conjunction with planewave basis sets and projector augmented-wave (PAW) pseudopotentials because of the complexity of the PAW "all-electron" wave function. We report a method for rigorous evaluation of the NAC with PAW wave functions and demonstrate an efficient approximation to the rigorous NAC that gives comparable accuracy. As a validation, we intensely examine the NAC matrix elements calculated using both pseudo- and all-electron wave functions under the PAW formalism in six representative systems. The approximate NAC obtained with pseudowave functions is close to the exact all-electron NAC, with the largest deviations observed when subshell d-electrons are involved in the transitions. The developed approach provides a rigorous and convenient methodology for the numerical computation of NAC in the Kohn-Sham theory framework.

Interlayer Polarization Explains Slow Charge Recombination in Two-Dimensional Halide Perovskites by Nonadiabatic Molecular Dynamics Simulation

Two-dimensional (2D) perovskites for applications in photovoltaics and optoelectronics are attracting a great deal of research interest. The nonradiative electron-hole (e-h) recombination is the major efficiency loss channel. Herein, we report a study of the thickness dependence of the e-h recombination dynamics in diamine-based 2D perovskite via ab initio NAMD. For multilayer structures, due to the emergence of spontaneous interlayer electric polarization, which is induced by the collective and correlated reorientation of methylammonium molecules, the electron and hole at the band edges are localized in different inorganic layers, suppressing the e-h recombination. Furthermore, a broad range of phonon excitation also inspired rapid pure dephasing related to the microscopic origin for longer recombination times. The combination of the two effects leads to the observation of a prolonged carrier lifetime in multilayer 2D perovskites, which is essential to understanding the nonradiative e-h recombination mechanism in such materials.