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. 2023 Nov 21;14(47):10685–10692. doi: 10.1021/acs.jpclett.3c02850

Lattice Distortion and Low-Frequency Anharmonic Phonons Suppress Charge Recombination in Lead Halide Perovskites upon Pseudohalide Doping: Time-Domain Ab Initio Analysis

Teng-Fei Lu †, Weibin Chu ‡, Sraddha Agrawal §, Zhihua Zhang †,*, Oleg V Prezhdo §,*
PMCID: PMC10694819  PMID: 37988630

Abstract

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Perovskite solar cells have witnessed a surge in interest as a promising technology for low-cost, high-efficiency photovoltaics with certified power conversion efficiencies beyond 25%. However, their commercial development is hindered by poor stability and nonradiative losses that restrict their approach to the theoretical efficiency limit. Using ab initio nonadiabatic molecular dynamics, we demonstrate that nonradiative charge recombination is suppressed when the iodide in formamidinium lead iodide (FAPbI3) is partially replaced with pseudohalide anions (SCN–, BF4–, and PF6–). The replacement breaks the symmetry of the system and creates local structural distortion and dynamic disorder, decreasing electron–hole overlap and nonadiabatic electron–vibrational coupling. The charge carrier lifetime is found to increase with increased structural distortion and is the longest for PF6–. This work is fundamentally relevant to the design of high-performance perovskite materials for optoelectronic applications.

Organic–inorganic hybrid perovskites (OIHPs) have emerged as one of the most promising semiconducting materials in the realm of photovoltaic research, owing to their outstanding optoelectronic properties, including high absorption coefficients, long charge carrier diffusion lengths, and ambipolar charge transport.1−4 These fine features render the applications of such perovskites to extend beyond solar energy harvesting into light-emitting diodes, lasers, transistors and detectors, etc.5−12 The power conversion efficiency (PCE) of OIHPs has witnessed a staggering increase since the first report of a methyl ammonium halide cell in 2009,13 from an initial value of 3.8%13 to 25.5%,14 which is comparable to that of conventional silicon-based solar cells. Despite the impressive progress in the performance, the currently achievable efficiency of these perovskite solar cells (PSCs) is still well below the theoretical Shockley–Queisser limit of 33%15 for a single-junction device, suggesting the presence of additional channels of energy losses other than radiative pathways. Often, the nonradiative recombination of charge carriers has been identified as the predominant pathway that limits device performance. This entails an urgent need to understand the underlying mechanisms of nonradiative recombination losses and the relationship between the perovskite structure and charge carrier dynamics at the atomistic level to further push the efficiency of PSCs toward the thermodynamic limit.

Three-dimensional (3D) perovskites have a general chemical formula of ABX3, where A stands for a monovalent cation (MA+ = CH3NH3+, FA+ = CH(NH2)2+, or Cs+), specifically an organic cation for OIHPs, B stands for a divalent metal cation (Sn2+ or Pb2+), and X is a halide anion (Cl–, Br–, or I–).16 Among OIHPs, methylammonium lead iodide (MAPbI3) is the most widely studied photovoltaic material. However, it is intrinsically thermally unstable due to its low formation energy.17 Formamidinium lead iodide (FAPbI3) is generally preferred over MAPbI3 because of its superior thermal stability and charge carrier transport properties.18,19 Unfortunately, practical applications of FAPbI3 are seriously limited by the spontaneous transformation from its photovoltaically active phase to the unwanted but more stable phase.20 Long-term stability under ambient photo and thermal stresses remains a critical bottleneck for the large-scale commercialization of PSCs.21 This challenge has motivated efforts to improve device stability, and significant advancements in this direction are being made by developing novel perovskite materials. Composition engineering, especially using mixed cations and halide anions, has proven to be a feasible and effective approach to achieve stable, high-performance PSCs.22,23 In particular, mixtures of MAPbI3 with FAPbI3 have been demonstrated to stabilize the active phase and suppress ion migration, achieving excellent transport characteristics.24 Calculations show that alkali metal dopants greatly improve perovskite performance by passivating interstitial defects, therefore extending carrier lifetimes.25 Compared to the amount of effort that has been put into building perovskites based on mixed cations and halides, not much focus has been placed on using molecular anions as alternatives to halogen anions to modulate the PCE.

Pseudohalides, which are polyatomic analogues of halides such as thiocyanate (SCN–), tetrafluoroborate (BF4–), and hexafluorophosphate (PF6–), can serve as alternatives for X-site halides in perovskites because their ionic radii and chemical properties are similar to those of true halides.26 A wider range of negatively charged anions (pseudohalides) may form the ABX3 stoichiometry with Pb2+. Zhang et al. reported that introducing the BF4– anion in a mixed-ion perovskite crystal frame resulted in a slight lattice relaxation, a longer photoluminescence lifetime, and improved charge transport in the perovskite solar cell.27 By utilizing relativistic electronic structure calculations, Hendon and co-authors demonstrated that substitution with BF4– and PF6– anions in hybrid perovskites can form wide bandgap dielectric compounds.28 Tai et al. reported that the incorporation of the SCN– anion as a dopant improved the moisture resistance and photovoltaic performance of PSC devices.29 Given these interesting findings, a systematic study on the detailed mechanism of PCE improvement with pseudohalides in OIHPs is needed. This can be achieved by an atomistic investigation of the structural and electronic properties, electron–vibrational interactions, and charge carrier dynamics.

Motivated by experimental studies, we report here an ab initio time domain investigation of the substitution by the pseudohalide anions PF6–, BF4–, and SCN– as “dopants” in FAPbI3 and provide a mechanistic understanding of the nonradiative electron–hole recombination and reduced charge and energy losses. We demonstrate that nonradiative charge recombination is suppressed in FAPbI3 doped with pseudohalide anions due to changes in the properties of the inorganic sublattice. Minor changes in the PbI3– octahedra can affect the electronic properties of the perovskite to a significant extent. The anion doping expands the inorganic sublattice, distorts the PbI3– octahedra, and creates structural asymmetries, which in turn change the electronic properties of the sublattice. Dynamically, the anion substitution activates low-frequency lattice vibrations that are responsible for transient disorder and decreased electron–hole interactions. The simulations illustrate that the synergistic effect of static and dynamic lattice disorder decreases NA coupling, thereby slowing the nonradiative electron–hole recombination in polyanion-substituted FAPbI3. The atomistic details of the mechanism of the nonradiative charge and energy losses provide guidelines for further improvement of the performance of hybrid perovskites.

To simulate the nonradiative recombination processes in the FAPbI3 perovskite with different pseudohalide dopants, we performed ab initio nonadiabatic molecular dynamics (NAMD) simulations with real-time time-dependent density functional theory (TD-DFT) in the Kohn–Sham representation.30−32 The lighter electrons were treated quantum-mechanically, whereas the heavier atoms were described semiclassically. The charge recombination dynamics were investigated using the decoherence-induced surface hopping (DISH) technique, which includes the loss of coherence within the electronic system due to coupling to quantum phonons.33,34 The decoherence time is estimated as the pure dephasing time using the optical response theory.35,36 In order to further reduce the computational cost, classical path approximation (CPA) was used,37 in which the atomic dynamics were assumed to be weakly dependent on the quantum state of the electronic subsystem, as compared to thermal atomic fluctuations. This methodology has already been widely applied to study excited-state dynamics in a broad range of systems, including perovskites.38−59

The ground-state geometry optimization, electronic structure calculations, and room-temperature MD were performed with the Vienna Ab Initio Simulation Package (VASP).60 The Perdew–Burke–Ernzerhof (PBE) exchange-correlation functional was adopted.61,62 The van der Waals interactions were described by the Grimme DFT-D3 method.63 Both the structural optimization and the adiabatic MD employed a 4 × 4 × 4 Γ-centered Monkhorst–Pack k-mesh grid.64 The NA couplings (NACs) were computed for the Γ-point, as the structures had direct bandgaps located at the Γ-point. The plane wave energy cutoff was 400 eV. The geometry optimization at 0 K was stopped when the Hellmann–Feynman forces on each atom were smaller than 0.01 eV/Å. Then, the systems were heated at 300 K through repeated velocity rescaling and further equilibrated for 6 ps with a 1 fs atomic time step in the NVE ensemble. Next, 500 initial conditions were selected randomly from the last 4 ps of the MD trajectories, and NAMD simulations were carried out using 1000 random number sequences to sample the surface hopping probabilities for each initial geometry. The NAMD simulations were performed with the Python eXtension for Ab Initio Dynamics (PYXAID) code.33,37

To investigate the electron–hole recombination dynamics in different pseudohalide anion-substituted perovskites, we first constructed a 96-atom (2 × 2 × 2) simulation supercell of the FAPbI3 cubic phase and generated pseudohalide-mixed perovskite structures through partial halide substitution. Figure 1 shows the optimized stoichiometric structure for pristine FAPbI3 (Figure 1a) and the substituted structures (Figures 1b–d), in which one of the I– ions has been replaced by BF4–, PF6–, or SCN–, respectively. The calculated averaged Pb–I bond length in the optimized pristine FAPbI3 was 3.174 Å, which is consistent with the experimental (3.181 Å) and theoretical (3.177 Å) data.65 After the pseudohalide anion substitution, the inorganic Pb–I sublattice around the doping site expands and the Pb–Pb distances increase (Table 1). Thus, the distances between the key Pb atoms, marked in Figure 1a, are 6.57, 6.98, and 7.26 Å for Pb1–Pb2 and 6.51, 6.56, and 6.61 Å for Pb2–Pb3 in ISCN, IBF4 and IPF6, respectively, as compared to 6.35 Å for Pb1–Pb2 and 6.50 Å for Pb2–Pb3 in FAPbI3. Structural fluctuations at room temperature led to a slight decrease in the canonically averaged Pb–Pb distances relative to the 0 K data; however, the dopant-induced expansion trend remained (Table 1).

Figure 1.

Figure 1

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Structures of (a) pristine FAPbI3, (b) FAPbI3 with IBF4, (c) FAPbI3 with IPF6, and (d) FAPbI3 with ISCN. The red circles indicate the sites where iodine atoms are substituted by the respective pseudohalide anions.

Table 1. Pb–Pb Distances aPb1–Pb2 and aPb2–Pb3 at 0 K and the Averaged Pb–Pb Distances bPb1–Pb2 and bPb2–Pb3 at 300 K around the Anion-Substituted Site (See Figure 1).

  aPb1–Pb2 (Å) aPb2–Pb3 (Å) bPb1–Pb2 (Å) bPb2–Pb3 (Å)
FAPbI3 6.35 6.50 6.32 6.46
IBF4 6.98 6.56 6.80 6.52
IPF6 7.26 6.61 7.16 6.60
ISCN 6.57 6.51 6.52 6.49
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The PF6– substitution showed the maximum increase in the Pb–Pb distances and the highest local lattice expansion among all of the systems. Distortion of the octahedral structure is known in mixed-ion perovskites,66,67 leading to lattice strain that balances different-sized cations/anions. The molecular orbitals of pseudohalides such as BF4– (tetrahedral shape) can weakly hybridize with the atomic orbitals of Pb2+ compared to iodide (spherical shape), and hydrogen bonds can form between pseudohalides and FA+. Such additional chemical bonding contributes to the improved chemical stability of the doped perovskites. The local expansion of the inorganic Pb–I sublattice modulates the electronic properties and electron–vibrational coupling, which in turn influences the electron–hole recombination.

The projected density of states (PDOS) of pristine FAPbI3 and the doped systems IPF6, IBF4, and ISCN are shown in Figure 2. The PDOS is separated into the FA, Pb, I, and pseudohalide contributions. The conduction band minimum (CBM) and valence band maximum (VBM) of perovskites are formed primarily by the Pb-6p and I-5p/Pb-6s atomic orbitals, respectively. The electronic states near the Fermi level are supported by the Pb and I atoms; therefore, the PbI6 octahedra determine the relevant electronic properties. Among all of the pseudohalide atoms, only the SCN– group makes a contribution to the valence band, although it is almost negligible. The pseudohalide anions do not contribute to the band edge states, and hence, they have no direct influence on the electron–hole recombination. They instead influence the recombination in an indirect way: by perturbing the structure and motions of the inorganic Pb–I framework.

Figure 2.

Figure 2

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Atom-projected DOS for (a) pristine FAPbI3 and the doped systems (b) IBF4, (c) IPF6, and (d) ISCN at 300 K. The energy reference is given at the Fermi level.

The calculated canonically averaged direct bandgap of pristine FAPbI3 was 1.80 eV, (Table 2), which is in agreement with previous DFT calculations.68 The canonically averaged bandgaps in the anion-substituted systems ranged from 1.82 to 1.86 eV, which are again consistent with the experimental trend.27 No additional electronic levels (traps) were introduced in the bandgap for the doped systems.

Table 2. Canonically Averaged Bandgap, Absolute NA Coupling, Pure Dephasing Time, and Nonradiative Electron–Hole Recombination Time.

  average bandgap (eV) NA coupling (meV) dephasing (fs) recombination (ns)
FAPbI3 1.80 0.426 9.03 6.36
IBF4 1.82 0.389 8.49 12.56
IPF6 1.86 0.353 9.06 15.62
ISCN 1.83 0.399 10.33 8.63
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The electron–hole recombination is determined primarily by electron–vibrational NA coupling (NAC). The NAC, djk, is calculated as the overlap between the electronic states j and k at sequential time steps:69,70

graphic file with name jz3c02850_m001.jpg 1

where H is the electronic Hamiltonian, φj, φk, εk, and εj are the wave functions and energies of the electronic states k and j, and Ṙ is the atomic velocity vector. The last expression demonstrates that the NAC is inversely proportional to the energy difference εk – εj, grows with the atomic velocity Ṙ (and hence temperature), and depends on the electron–vibrational coupling matrix element ⟨φj|∇RH|φk⟩. The latter depends on the relative localization of the two wave functions, which are sensitive to composition and thermal disorder.71−73 The CBM and VBM charge densities, which characterize the localization of electrons and holes, are shown in Figure 3. Figure 3a demonstrates that in pristine FAPbI3, the VBM is localized primarily on I atoms, while the CBM is distributed over Pb atoms, which is consistent with the PDOS analysis (Figure 2). The localization of the CBM and the VBM on different atoms is beneficial for achieving a decreased wave function overlap and a small NAC. The anion substitution influences the localization of both the VBM and the CBM. Because the VBM is supported by iodides, by removing an iodide, the anions also remove the hole density from the corresponding spatial region. The CBM is influenced indirectly by the distortion of the Pb sublattice. Overall, the electron and hole wave functions become more localized upon pseudohalide doping. Provided that they are not being localized in the same place, their overlap should be reduced and the NAC decreased. Indeed, the NAC decreases in the following order (Table 2): FAPbI3 > ISCN > IBF4 > IPF6, suggesting that the charge carrier lifetime should increase in this same order. The NAC trend correlates with the changes in the Pb–Pb distances (Table 1). The largest change in IPF6 leads to the smallest NAC.

Figure 3.

Figure 3

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Orbital spatial charge densities of the VBM and CBM for the representative configuration at 300 K in (a) FAPbI3, (b) IBF4, (c) IPF6, and (d) ISCN.

Excess electronic energy is accommodated by phonons during nonradiative charge recombination. Electron–vibrational interactions generate elastic and inelastic scattering, both affecting the excited-state lifetime. Inelastic electron–phonon scattering leads to an energy exchange between the electronic and vibrational subsystems and is characterized by the NAC. Significant amounts of electronic energy are deposited into atomic degrees of freedom during nonradiative charge recombination. Elastic electron–phonon scattering destroys the coherence formed between the initial and final states. Because the formation of coherence is necessary for a quantum process to occur, fast decoherence can drastically slow down electron–hole recombination.74,75

In order to identify the vibrational motions that couple to the electronic transition across the bandgap, we computed Fourier transforms of autocorrelation functions (ACFs) of the bandgap fluctuations, δE(t), from its canonically averaged values:

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The obtained spectral densities

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are reported in Figure 4. Several modes in the 30–300 cm–1 frequency range couple to the electronic transition, including vibrations arising from the inorganic Pb–I framework, the organic FA cation, and the pseudohalide anions. The main high-intensity peaks that are observed at low frequencies (<100 cm–1) can be attributed to the bending and stretching modes of the slow Pb–I framework, which generates the NAC. The peaks at higher frequencies are much weaker in amplitude and arise from motions of the organic cations. FA and the pseudohalides contain light atoms and move much faster than the Pb–I framework; however, they do not contribute to the band edge states. Their influence on the electron–hole recombination is indirect, through coupling to the Pb–I lattice. The influence spectra shift to lower frequencies in the presence of the pseudohalide anions (Figure 4). The peak around 30 cm–1 is related to the octahedron distortion in the doped systems. Lower-frequency motions exhibit smaller atomic velocities (at a given temperature), hence reducing the NAC, which is proportional to the velocity (eq 1. Furthermore, low-frequency motions create dynamic disorder, which partially localizes the electron and hole wave functions and reduces the NAC as well.76,77

Figure 4.

Figure 4

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Spectral densities obtained by Fourier transforms of fluctuations of the electron–hole energy gaps in FAPbI3 (a), IBF4 (b), IPF6(c), and ISCN (d).

Figure 5 presents the pure dephasing functions D(t) for electron–hole recombination in FAPbI3, IBF4, IPF6, and ISCN, which were computed using the second-order cumulant approximation of the optical response theory:35

graphic file with name jz3c02850_m004.jpg 4

Here, C(t) is the unnormalized ACF (eq 2). Fitting the functions to a Gaussian, exp[−0.5(t/τ)]2 gives the pure dephasing times τ, as reported in Table 2. The short 10 fs coherence times contribute to the long-lived excited-state lifetime in perovskites, as exemplified by the quantum Zeno effect,74 according to which quantum dynamics stops in the limit of infinitely fast decoherence. The coherence times are short because the electrons and holes are weakly correlated. They are localized on different atoms, Pb and I, and couple to a broad range of anharmonic76,77 vibrations (Figure 4). The disorder introduced by the pseudohalide dopants slightly shortens the coherence times. The pure dephasing times can be correlated to the ACF initial values (insert in Figure 5), which are equal to the square root of the electronic bandgap fluctuation. Generally, greater unnormalized ACF initial values lead to faster pure dephasing times.35 Thus, the initial ACF value is the largest for IBF4, and the corresponding pure dephasing time is the shortest. The pure dephasing time is the longest for pristine FAPbI3, but the corresponding initial ACF value is not the smallest. Coherence is the longest for pristine FAPbI3 because the ACF shows the most regular oscillation among the four systems, and the positive and negative ACF contributions to the integral in eq 4 cancel the most.

Figure 5.

Figure 5

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Pure dephasing functions for electron–hole recombination in FAPbI3, IBF4, IPF6, and ISCN. The inset shows the unnormalized autocorrelation functions, whose initial values are the bandgap fluctuations squared.

Nonradiative charge carrier recombination depends primarily on the NAC, which is governed by the relative localization of the initial and final (electron and hole) wave functions, the energy gap, and the atomic velocity (eq 1). The pure dephasing times also influence the recombination; however, they were very similar (Table 2). The bandgaps were similar as well. All of the systems were considered at the same temperature, and therefore, the atomic velocity was smaller for lower-frequency motions (Figure 4). The overlap of the electron and hole wave functions depends on structural disorder. The pseudohalide doping increased the disorder and shifted the spectral density to lower frequencies, which both contributed to the observed longer recombination times. The evolution of the excited-state populations during the nonradiative electron–hole recombination dynamics are shown in Figure 6. The nonradiative decay times, reported in Table 2, were obtained by fitting the data to the short-time linear approximation of the exponential decay: P(t) = exp(−t/τ) ≈ 1 – t/τ. The results confirm the expectation based on the above analysis. All of the pseudohalides slowed the charge carrier recombination, with the longest lifetime observed for PF6–. Its lifetime increased by a factor of 2.5 relative to that of pristine FAPbI3. PF6– created the largest local lattice distortion (Table 1), breaking the lattice symmetry and reducing the electron–hole overlap the most. The overall recombination was slow because the NA coupling was small (4 meV) and the pure dephasing time was short (10 fs).

Figure 6.

Figure 6

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Electron–hole recombination dynamics in FAPbI3, IBF4, IPF6, and ISCN.

In conclusion, we performed NAMD simulations combined with real-time TD-DFT to investigate nonradiative charge carrier recombination in FAPbI3 doped with three pseudohalide anions: SCN–, BF4–, and PF6–. Using these anions as a substitute for an iodide in FAPbI3 created a local structural distortion and shifted the relevant vibrations to lower frequencies. Consequently, the electrons and holes became partially localized and overlapped less, while at the same time, the atomic motions driving the nonradiative charge recombination became slower. Both of these factors reduced the NAC responsible for the recombination, and the excited-state lifetime became longer. The lifetime correlated directly with the pseudohalide-induced local structural distortion and increased in the order of FAPbI3 < SCN– < BF4– < PF6–. The bandgap and the pure dephasing times, which also influence the charge carrier lifetime, changed little upon pseudohalide doping. Overall, the nonradiative processes were slow because they were driven by low-frequency anharmonic motions of the heavy Pb–I inorganic lattice and because the electrons and holes were localized on different widely spaced atoms, Pb and I, and overlapped little. The NAC coupling was weak, being only a few meV, and the quantum coherence was short (10 fs); both of these factors favor long lifetimes. The low-frequency anharmonic motions created dynamic disorder, which was enhanced by the dopants, further decreasing the electron–hole overlap. The atomistic analysis of the mechanisms of charge and energy losses in metal halide perovskites provided by the current study contributes to the fundamental understanding of perovskite properties, which is needed for the rational design of efficient solar energy and optoelectronic materials.

Acknowledgments

O.V.P. acknowledges the support from the U.S. Department of Energy, Grant DE-SC0014429. T.-F.L. acknowledges the support from the Dalian Science and Technology Innovation Fund, Grant 2023RQ039.

The authors declare no competing financial interest.

References

  1. Boyd C. C.; Cheacharoen R.; Leijtens T.; McGehee M. D. Understanding Degradation Mechanisms and Improving Stability of Perovskite Photovoltaics. Chem. Rev. 2019, 119, 3418–3451. 10.1021/acs.chemrev.8b00336. [DOI] [PubMed] [Google Scholar]
  2. Jena A. K.; Kulkarni A.; Miyasaka T. Halide Perovskite Photovoltaics: Background, Status, and Future Prospects. Chem. Rev. 2019, 119, 3036–3103. 10.1021/acs.chemrev.8b00539. [DOI] [PubMed] [Google Scholar]
  3. Kim J. Y.; Lee J. W.; Jung H. S.; Shin H.; Park N. G. High-Efficiency Perovskite Solar Cells. Chem. Rev. 2020, 120, 7867–7918. 10.1021/acs.chemrev.0c00107. [DOI] [PubMed] [Google Scholar]
  4. Duan L. P.; Walter D.; Chang N. T.; Bullock J.; Kang D.; Phang S. P.; Weber K.; White T.; Macdonald D.; Catchpole K.; Shen H. P. Stability Challenges for the Commercialization of Perovskite-Silicon Tandem Solar Cells. Nat. Rev. Mater. 2023, 8, 261–281. 10.1038/s41578-022-00521-1. [DOI] [Google Scholar]
  5. Saliba M.; Wood S. M.; Patel J. B.; Nayak P. K.; Huang J.; Alexander-Webber J. A.; Wenger B.; Stranks S. D.; Horantner M. T.; Wang J. T.; Nicholas R. J.; Herz L. M.; Johnston M. B.; Morris S. M.; Snaith H. J.; Riede M. K. Structured Organic-Inorganic Perovskite toward a Distributed Feedback Laser. Adv. Mater. 2016, 28, 923. 10.1002/adma.201502608. [DOI] [PubMed] [Google Scholar]
  6. Kao T. S.; Chou Y. H.; Hong K. B.; Huang J. F.; Chou C. H.; Kuo H. C.; Chen F. C.; Lu T. C. Controllable Lasing Performance in Solution-Processed Organic-Inorganic Hybrid Perovskites. Nanoscale 2016, 8, 18483–18488. 10.1039/C6NR05561C. [DOI] [PubMed] [Google Scholar]
  7. Li Z. Q.; Hong E. L.; Zhang X. Y.; Deng M.; Fang X. S. Perovskite-Type 2D Materials for High-Performance Photodetectors. J. Phys. Chem. Lett. 2022, 13, 1215–1225. 10.1021/acs.jpclett.1c04225. [DOI] [PubMed] [Google Scholar]
  8. Park Y. J.; Lee J. S. Metal Halide Perovskite-Based Memristors for Emerging Memory Applications. J. Phys. Chem. Lett. 2022, 13, 5638–5647. 10.1021/acs.jpclett.2c01303. [DOI] [PubMed] [Google Scholar]
  9. Guner T.; Demir M. M. A Review on Halide Perovskites as Color Conversion Layers in White Light Emitting Diode Applications. Phys. Status Solidi A 2018, 215, 1800120. 10.1002/pssa.201800120. [DOI] [Google Scholar]
  10. Wang C.; Sun M. J.; Wang H.; Zhao G. J. Cubic Halide Double Perovskite Nanocrystals with Anisotropic Free Excitons and Self-Trapped Exciton Photoluminescence. J. Phys. Chem. Lett. 2023, 14, 164–169. 10.1021/acs.jpclett.2c03482. [DOI] [PubMed] [Google Scholar]
  11. Aamir M.; Khan M. D.; Sher M.; Bhosale S. V.; Malik M. A.; Akhtar J.; Revaprasadu N. A Facile Route to Cesium Lead Bromoiodide Perovskite Microcrystals and Their Potential Application as Sensors for Nitrophenol Explosives. Eur. J. Inorg. Chem. 2017, 2017, 3755–3760. 10.1002/ejic.201700660. [DOI] [Google Scholar]
  12. Xie M. Y.; Tian J. J. Operational Stability Issues and Challenges in Metal Halide Perovskite Light-Emitting Diodes. J. Phys. Chem. Lett. 2022, 13, 1962–1971. 10.1021/acs.jpclett.1c04210. [DOI] [PubMed] [Google Scholar]
  13. Kojima A.; Teshima K.; Shirai Y.; Miyasaka T. Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc. 2009, 131, 6050. 10.1021/ja809598r. [DOI] [PubMed] [Google Scholar]
  14. Jeong J.; Kim M.; Seo J.; Lu H.; Ahlawat P.; Mishra A.; Yang Y.; Hope M. A.; Eickemeyer F. T.; Kim M.; Yoon Y. J.; Choi I. W.; Darwich B. P.; Choi S. J.; Jo Y.; Lee J. H.; Walker B.; Zakeeruddin S. M.; Emsley L.; Rothlisberger U.; Hagfeldt A.; Kim D. S.; Gratzel M.; Kim J. Y. Pseudo-Halide Anion Engineering for Alpha-FAPbI3 Perovskite Solar Cells. Nature 2021, 592, 381–385. 10.1038/s41586-021-03406-5. [DOI] [PubMed] [Google Scholar]
  15. Shockley W.; Queisser H. J. Detailed Balance Limit of Efficiency of P-N Junction Solar Cells. J. Appl. Phys. 1961, 32, 510–519. 10.1063/1.1736034. [DOI] [Google Scholar]
  16. Qiu L.; He S.; Ono L. K.; Qi Y. Progress of Surface Science Studies on ABX3– Based Metal Halide Perovskite Solar Cells. Adv. Energy Mater. 2020, 10, 1902726. 10.1002/aenm.201902726. [DOI] [Google Scholar]
  17. Wang X.; Wang Y.; Zhang T.; Liu X.; Zhao Y. Steric Mixed-Cation 2D Perovskite as a Methylammonium Locker to Stabilize MAPbI3. Angew. Chem. 2020, 132, 1485–1489. 10.1002/ange.201911518. [DOI] [PubMed] [Google Scholar]
  18. Min H.; Kim M.; Lee S. U.; Kim H.; Kim G.; Choi K.; Lee J. H.; Seok S. I. Efficient, Stable Solar Cells by Using Inherent Bandgap of Alpha-Phase Formamidinium Lead Iodide. Science 2019, 366, 749–753. 10.1126/science.aay7044. [DOI] [PubMed] [Google Scholar]
  19. Akin S.; Akman E.; Sonmezoglu S. FAPbI3 Based Perovskite Solar Cells Employing Hexyl-Based Ionic Liquid with an Efficiency Over 20% and Excellent Long-Term Stability. Adv. Funct. Mater. 2020, 30, 2002964. 10.1002/adfm.202002964. [DOI] [Google Scholar]
  20. Masi S.; Gualdrón-Reyes A. F.; Mora-Seró I. Stabilization of Black Perovskite Phase in FAPbI3 and CsPbI3. ACS Energy Lett. 2020, 5, 1974–1985. 10.1021/acsenergylett.0c00801. [DOI] [Google Scholar]
  21. Roy P.; Kumar Sinha N.; Tiwari S.; Khare A. A Review on Perovskite Solar Cells: Evolution of Architecture, Fabrication Techniques, Commercialization Issues and Status. Sol. Energy 2020, 198, 665–688. 10.1016/j.solener.2020.01.080. [DOI] [Google Scholar]
  22. Yu B.-B.; Liao M.; Zhu Y.; Zhang X.; Du Z.; Jin Z.; Liu D.; Wang Y.; Gatti T.; Ageev O.; He Z. Oriented Crystallization of Mixed-Cation Tin Halides for Highly Efficient and Stable Lead-Free Perovskite Solar Cells. Adv. Funct. Mater. 2020, 30, 2002230. 10.1002/adfm.202002230. [DOI] [Google Scholar]
  23. Yang J.; Wang Y.; Wu T.; Li S. Correlating the Composition-Dependent Structural and Electronic Dynamics of Inorganic Mixed Halide Perovskites. Chem. Mater. 2020, 32, 2470–2481. 10.1021/acs.chemmater.9b04995. [DOI] [Google Scholar]
  24. Lu H.; Krishna A.; Zakeeruddin S. M.; Gratzel M.; Hagfeldt A. Compositional and Interface Engineering of Organic-Inorganic Lead Halide Perovskite Solar Cells. iScience 2020, 23, 101359. 10.1016/j.isci.2020.101359. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Qiao L.; Fang W. H.; Long R.; Prezhdo O. V. Extending Carrier Lifetimes in Lead Halide Perovskites with Alkali Metals by Passivating and Eliminating Halide Interstitial Defects. Angew. Chem. 2020, 132, 4714–4720. 10.1002/ange.201911615. [DOI] [PubMed] [Google Scholar]
  26. Walker B.; Kim G.-H.; Kim J. Y. Pseudohalides in Lead-Based Perovskite Semiconductors. Adv. Mater. 2019, 31, 1807029. 10.1002/adma.201807029. [DOI] [PubMed] [Google Scholar]
  27. Zhang J.; Wu S.; Liu T.; Zhu Z.; Jen A. K.-Y. Boosting Photovoltaic Performance for Lead Halide Perovskites Solar Cells with BF4– Anion Substitutions. Adv. Funct. Mater. 2019, 29, 1808833. 10.1002/adfm.201808833. [DOI] [Google Scholar]
  28. Hendon C. H.; Yang R. X.; Burton L. A.; Walsh A. Assessment of Polyanion (BF4–and PF6–) Substitutions in Hybrid Halide Perovskites. J. Mater. Chem. A 2015, 3, 9067–9070. 10.1039/C4TA05284F. [DOI] [Google Scholar]
  29. Tai Q.; You P.; Sang H.; Liu Z.; Hu C.; Chan H. L.; Yan F. Efficient and Stable Perovskite Solar Cells Prepared in Ambient Air Irrespective of the Humidity. Nat. Commun. 2016, 7, 11105. 10.1038/ncomms11105. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Craig C. F.; Duncan W. R.; Prezhdo O. V. Trajectory Surface Hopping in the Time-Dependent Kohn-Sham Approach for Electron-Nuclear Dynamics. Phys. Rev. Lett. 2005, 95, 163001. 10.1103/PhysRevLett.95.163001. [DOI] [PubMed] [Google Scholar]
  31. Fischer S. A.; Habenicht B. F.; Madrid A. B.; Duncan W. R.; Prezhdo O. V. Regarding the Validity of the Time-Dependent Kohn-Sham Approach for Electron-Nuclear Dynamics Via Trajectory Surface Hopping. J. Chem. Phys. 2011, 134, 024102. 10.1063/1.3526297. [DOI] [PubMed] [Google Scholar]
  32. Prezhdo O. V. Modeling Non-adiabatic Dynamics in Nanoscale and Condensed Matter Systems. Acc. Chem. Res. 2021, 54, 4239–4249. 10.1021/acs.accounts.1c00525. [DOI] [PubMed] [Google Scholar]
  33. Akimov A. V.; Prezhdo O. V. Advanced Capabilities of the PYXAID Program: Integration Schemes,Decoherence Effects, Multiexcitonic States, and Field-Matter Interaction. J. Chem. Theory Comput. 2014, 10, 789–804. 10.1021/ct400934c. [DOI] [PubMed] [Google Scholar]
  34. Jaeger H. M.; Fischer S.; Prezhdo O. V. Decoherence-Induced Surface Hopping. J. Chem. Phys. 2012, 137, 22A545. 10.1063/1.4757100. [DOI] [PubMed] [Google Scholar]
  35. Akimov A. V.; Prezhdo O. V. Persistent Electronic Coherence Despite Rapid Loss of Electron-Nuclear Correlation. J. Phys. Chem. Lett. 2013, 4, 3857–3864. 10.1021/jz402035z. [DOI] [Google Scholar]
  36. Kamisaka H.; Kilina S. V.; Yamashita K.; Prezhdo O. V. Ultrafast Vibrationally-Induced Dephasing of Electronic Excitations in PbSe Quantum Dot. Nano Lett. 2006, 6, 2295–2300. 10.1021/nl0617383. [DOI] [PubMed] [Google Scholar]
  37. Akimov A. V.; Prezhdo O. V. The PYXAID Program for Non-Adiabatic Molecular Dynamics in Condensed Matter Systems. J. Chem. Theory Comput. 2013, 9, 4959. 10.1021/ct400641n. [DOI] [PubMed] [Google Scholar]
  38. Prezhdo O. V.; Rossky P. J. Solvent Mode Participation in the Nonradiative Relaxation of the Hydrated Electron. J. Chem. Phys. 1996, 100, 17094–17102. 10.1021/jp9611232. [DOI] [Google Scholar]
  39. Stier W.; Duncan W. R.; Prezhdo O. V. Thermally Assisted Sub-10 fs Electron Transfer in Dye-Sensitized Nanocrystalline TiO2 Solar Cells. Adv. Mater. 2004, 16, 240. 10.1002/adma.200306027. [DOI] [Google Scholar]
  40. Wang L. J.; Prezhdo O. V.; Beljonne D. Mixed Quantum-Classical Dynamics for Charge Transport in Organics. Phys. Chem. Chem. Phys. 2015, 17, 12395–12406. 10.1039/C5CP00485C. [DOI] [PubMed] [Google Scholar]
  41. Li L. Q.; Long R.; Prezhdo O. V. Why Chemical Vapor Deposition Grown MoS2 Samples Outperform Physical Vapor Deposition Samples: Time-Domain ab Initio Analysis. Nano Lett. 2018, 18, 4008–4014. 10.1021/acs.nanolett.8b01501. [DOI] [PubMed] [Google Scholar]
  42. Liu L. H.; Fang W. H.; Long R.; Prezhdo O. V. Lewis Base Passivation of Hybrid Halide Perovskites Slows Electron-Hole Recombination: Time-Domain Ab lnitio Analysis. J. Phys. Chem. Lett. 2018, 9, 1164–1171. 10.1021/acs.jpclett.8b00177. [DOI] [PubMed] [Google Scholar]
  43. Zhang L. L.; Vasenko A. S.; Zhao J.; Prezhdo O. V. Mono-Elemental Properties of 2D Black Phosphorus Ensure Extended Charge Carrier Lifetimes under Oxidation: Time-Domain Ab Initio Analysis. J. Phys. Chem. Lett. 2019, 10, 1083. 10.1021/acs.jpclett.9b00042. [DOI] [PubMed] [Google Scholar]
  44. Zhang Z. S.; Fang W. H.; Long R.; Prezhdo O. V. Exciton Dissociation and Suppressed Charge Recombination at 2D Perovskite Edges: Key Roles of Unsaturated Halide Bonds and Thermal Disorder. J. Am. Chem. Soc. 2019, 141, 15557–15566. 10.1021/jacs.9b06046. [DOI] [PubMed] [Google Scholar]
  45. Lu T. F.; Wang Y. S.; Tomko J. A.; Hopkins P. E.; Zhang H. X.; Prezhdo O. V. Control of Charge Carrier Dynamics in Plasmonic Au Films by TiOx Substrate Stoichiometry. J. Phys. Chem. Lett. 2020, 11, 1419–1427. 10.1021/acs.jpclett.9b03884. [DOI] [PubMed] [Google Scholar]
  46. Chu W.; Saidi W. A.; Prezhdo O. V. Long-Lived Hot Electron in a Metallic Particle for Plasmonics and Catalysis: Ab Initio Nonadiabatic Molecular Dynamics with Machine Learning. ACS Nano 2020, 14, 10608–10615. 10.1021/acsnano.0c04736. [DOI] [PubMed] [Google Scholar]
  47. Zhou G.; Lu G.; Prezhdo O. V. Modeling Auger Processes with Nonadiabatic Molecular Dynamics. Nano Lett. 2021, 21, 756–761. 10.1021/acs.nanolett.0c04442. [DOI] [PubMed] [Google Scholar]
  48. Lu T. F.; Gumber S.; Tokina M. V.; Tomko J. A.; Hopkins P. E.; Prezhdo O. V. Electron-Phonon Relaxation at the Au/WSe2 Interface is Significantly Accelerated by a Ti Adhesion Layer: Time-Domain Ab Initio Analysis. Nanoscale 2022, 14, 10514–10523. 10.1039/D2NR00728B. [DOI] [PubMed] [Google Scholar]
  49. Agrawal S.; Vasenko A. S.; Trivedi D. J.; Prezhdo O. V. Charge Carrier Nonadiabatic Dynamics in Non-Metal Doped Graphitic Carbon Nitride. J. Chem. Phys. 2022, 156, 094702. 10.1063/5.0079085. [DOI] [PubMed] [Google Scholar]
  50. Liu D. Y.; Wu Y. F.; Vasenko A. S.; Prezhdo O. V. Grain Boundary Dliding and Distortion on a Nanosecond Timescale Induce Trap States in CsPbBr3: Ab Initio Investigation with Machine Learning Force Field. Nanoscale 2022, 15, 285–293. 10.1039/D2NR05918E. [DOI] [PubMed] [Google Scholar]
  51. Shi R.; Fang W. H.; Vasenko A. S.; Long R.; Prezhdo O. V. Efficient Passivation of DY Center in CH3NH3PbBr3 by Chlorine: Quantum Molecular Dynamics. Nano Res. 2022, 15, 2112–2122. 10.1007/s12274-021-3840-y. [DOI] [Google Scholar]
  52. Zhu Y. H.; Fang W. H.; Rubio A.; Long R.; Prezhdo O. V. The Twist Angle has Weak Influence on Charge Separation and Strong Influence on Recombination in the MoS2/WS2 Bilayer: Ab Initio Quantum Dynamics. J. Mater. Chem. A 2022, 10, 8324–8333. 10.1039/D1TA10788G. [DOI] [Google Scholar]
  53. Liu D. Y.; Perez C. M.; Vasenko A. S.; Prezhdo O. V. Ag-Bi Charge Redistribution Creates Deep Traps in Defective Cs2AgBiBr6: Machine Learning Analysis of Density Functional Theory. J. Phys. Chem. Lett. 2022, 13, 3645–3651. 10.1021/acs.jpclett.2c00869. [DOI] [PubMed] [Google Scholar]
  54. Prezhdo O. V.; Wu Y. F.; Liu D. Y.; Chu W. B.; Wang B. P.; Vasenko A. S. Fluctuations at Metal Halide Perovskite Grain Boundaries Create Transient Trap States: Machine Learning Assisted Ab Initio Analysis. ACS Appl. Mater. Interfaces 2022, 14, 55753–55761. 10.1021/acsami.2c16203. [DOI] [PubMed] [Google Scholar]
  55. Zhou Z. B.; Zheng Z. F.; He J. J.; Wang J. L.; Prezhdo O. V.; Frauenheim T. Ultrafast Laser Control of Antiferromagnetic-Ferrimagnetic Switching in Two-Dimensional Ferromagnetic Semiconductor Heterostructures. Nano Lett. 2023, 23, 5688–5695. 10.1021/acs.nanolett.3c01350. [DOI] [PubMed] [Google Scholar]
  56. Xu C.; Zhou G. Q.; Alexeev E. M.; Cadore A. R.; Paradisanos I.; Ott A. K.; Soavi G.; Tongay S.; Cerullo G.; Ferrari A. C.; Prezhdo O. V.; Loh Z. H. Ultrafast Electronic Relaxation Dynamics of Atomically Thin MoS2 is Accelerated by Wrinkling. Acs Nano 2023, 17, 16682–16694. 10.1021/acsnano.3c02917. [DOI] [PubMed] [Google Scholar]
  57. Zhu Y. H.; Prezhdo O. V.; Long R.; Fang W. H. Twist Angle-Dependent Intervalley Charge Carrier Transfer and Recombination in Bilayer WS2. J. Am. Chem. Soc. 2023, 145, 22826–22835. 10.1021/jacs.3c09170. [DOI] [PubMed] [Google Scholar]
  58. Li W.; Xue T.; Mora-Perez C.; Prezhdo O. V. Ab Initio qQuantum Dynamics of Plasmonic Charge Carriers. Trends Chem. 2023, 5, 634–645. 10.1016/j.trechm.2023.02.010. [DOI] [Google Scholar]
  59. Lu T.-F.; Agrawal S.; Tokina M.; Chu W.; Hirt D.; Hopkins P. E.; Prezhdo O. V. Control of Charge Carrier Relaxation at the Au/WSe2 Interface by Ti and TiO2 Adhesion Layers: Ab Initio Quantum Dynamics. ACS Appl. Mater. Interfaces 2022, 14, 57197–57205. 10.1021/acsami.2c18793. [DOI] [PubMed] [Google Scholar]
  60. Kresse G.; Hafner J. Ab Initio Molecular Dynamics for Liquid Metals. Phys. Rev. B: Condens. Matter 1993, 47, 558–561. 10.1103/PhysRevB.47.558. [DOI] [PubMed] [Google Scholar]
  61. Blochl P. E. Projector Augmented-Wave Method. Phys. Rev. B: Condens. Matter 1994, 50, 17953–17979. 10.1103/PhysRevB.50.17953. [DOI] [PubMed] [Google Scholar]
  62. Perdew J. P.; Burke K.; Ernzerhof M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865–3868. 10.1103/PhysRevLett.77.3865. [DOI] [PubMed] [Google Scholar]
  63. Grimme S.; Antony J.; Ehrlich S.; Krieg H. A Consistent and Accurate Ab Initio Parametrization of Density Functional Dispersion Correction (DFT-D) for the 94 Elements H-Pu. J. Chem. Phys. 2010, 132, 154104. 10.1063/1.3382344. [DOI] [PubMed] [Google Scholar]
  64. Monkhorst H. J.; Pack J. D. Special Points for Brillouin-Zone Integrations. Phys. Rev. B 1976, 13, 5188–5192. 10.1103/PhysRevB.13.5188. [DOI] [Google Scholar]
  65. He J.; Long R. Lead Vacancy Can Explain the Suppressed Nonradiative Electron-Hole Recombination in FAPbI3 Perovskite under Iodine-Rich Conditions: A Time-Domain Ab Initio Study. J. Phys. Chem. Lett. 2018, 9, 6489–6495. 10.1021/acs.jpclett.8b03095. [DOI] [PubMed] [Google Scholar]
  66. He J. L.; Fang W. H.; Long R.; Prezhdo O. V. Increased Lattice Stiffness Suppresses Nonradiative Charge Recombination in MAPbl3 Doped with Larger Cations: Time Domain Ab Initio Analysis. ACS Energy Lett. 2018, 3, 2070. 10.1021/acsenergylett.8b01191. [DOI] [Google Scholar]
  67. Zhao X.; Vasenko A. S.; Prezhdo O. V.; Long R. Anion Doping Delays Nonradiative Electron-Hole Recombination in Cs-Based All-Inorganic Perovskites: Time Domain ab Initio Analysis. J. Phys. Chem. Lett. 2022, 13, 11375–11382. 10.1021/acs.jpclett.2c03072. [DOI] [PubMed] [Google Scholar]
  68. Ghosh D.; Perez C. M.; Prezhdo O.; Nie W.; Tretiak S.; Neukirch A. J. Impact of Composition Engineering on Charge Carrier Cooling in Hybrid Perovskites: Computational Insights. J. Mater. Chem. C 2022, 10, 9563–9572. 10.1039/D2TC01413K. [DOI] [Google Scholar]
  69. Chu W.; Prezhdo O. V. Concentric Approximation for Fast and Accurate Numerical Evaluation of Nonadiabatic Coupling with Projector Augmented-Wave Pseudopotentials. J. Phys. Chem. Lett. 2021, 12, 3082–3089. 10.1021/acs.jpclett.0c03853. [DOI] [PubMed] [Google Scholar]
  70. Chu W.; Zheng Q.; Akimov A. V.; Zhao J.; Saidi W. A.; Prezhdo O. V. Accurate Computation of Nonadiabatic Coupling with Projector Augmented-Wave Pseudopotentials. J. Phys. Chem. Lett. 2020, 11, 10073–10080. 10.1021/acs.jpclett.0c03080. [DOI] [PubMed] [Google Scholar]
  71. Mangan S. M.; Zhou G. Q.; Chu W. B.; Prezhdo O. V. Dependence between Structural and Electronic Properties of CsPbI3: Unsupervised Machine Learning of Nonadiabatic Molecular Dynamics. J. Phys. Chem. Lett. 2021, 12, 8672–8678. 10.1021/acs.jpclett.1c02361. [DOI] [PubMed] [Google Scholar]
  72. Zhou G.; Chu W.; Prezhdo O. V. Structural Deformation Controls Charge Losses in MAPbI3: Unsupervised Machine Learning of Nonadiabatic Molecular Dynamics. ACS Energy Lett. 2020, 5, 1930–1938. 10.1021/acsenergylett.0c00899. [DOI] [Google Scholar]
  73. Long R.; Fang Q.; Vasenko A. S.; Shi R.; Fang W. H.; Prezhdo O. V. Structural Disorder in Higher-Temperature Phases Increases Charge Carrier Lifetimes in Metal Halide Perovskites. J. Am. Chem. Soc. 2022, 144, 19137–19149. 10.1021/jacs.2c08627. [DOI] [PubMed] [Google Scholar]
  74. Kilina S. V.; Neukirch A. J.; Habenicht B. F.; Kilin D. S.; Prezhdo O. V. Quantum Zeno Effect Rationalizes the Phonon Bottleneck in Semiconductor Quantum Dots. Phys. Rev. Lett. 2013, 110, 180404. 10.1103/PhysRevLett.110.180404. [DOI] [PubMed] [Google Scholar]
  75. Gumber S.; Prezhdo O. V. Zeno and Anti-Zeno Effects in Nonadiabatic Molecular Dynamics. J. Phys. Chem. Lett. 2023, 14, 7274–7282. 10.1021/acs.jpclett.3c01831. [DOI] [PMC free article] [PubMed] [Google Scholar]
  76. Chu W.; Saidi W. A.; Zhao J.; Prezhdo O. V. Soft Lattice and Defect Covalency Rationalize Tolerance of beta-CsPbI3 Perovskite Solar Cells to Native Defects. Angew. Chem., Int. Ed. 2020, 59, 6435–6441. 10.1002/anie.201915702. [DOI] [PubMed] [Google Scholar]
  77. Li W.; Vasenko A. S.; Tang J. F.; Prezhdo O. V. Anharmonicity Extends Carrier Lifetimes in Lead Halide Perovskites at Elevated Temperatures. J. Phys. Chem. Lett. 2019, 10, 6219–6226. 10.1021/acs.jpclett.9b02553. [DOI] [PubMed] [Google Scholar]

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