1
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Toldo JM, do Casal MT, Ventura E, do Monte SA, Barbatti M. Surface hopping modeling of charge and energy transfer in active environments. Phys Chem Chem Phys 2023; 25:8293-8316. [PMID: 36916738 PMCID: PMC10034598 DOI: 10.1039/d3cp00247k] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 03/01/2023] [Indexed: 03/05/2023]
Abstract
An active environment is any atomic or molecular system changing a chromophore's nonadiabatic dynamics compared to the isolated molecule. The action of the environment on the chromophore occurs by changing the potential energy landscape and triggering new energy and charge flows unavailable in the vacuum. Surface hopping is a mixed quantum-classical approach whose extreme flexibility has made it the primary platform for implementing novel methodologies to investigate the nonadiabatic dynamics of a chromophore in active environments. This Perspective paper surveys the latest developments in the field, focusing on charge and energy transfer processes.
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Affiliation(s)
| | | | - Elizete Ventura
- Departamento de Química, CCEN, Universidade Federal da Paraíba, 58059-900, João Pessoa, Brazil.
| | - Silmar A do Monte
- Departamento de Química, CCEN, Universidade Federal da Paraíba, 58059-900, João Pessoa, Brazil.
| | - Mario Barbatti
- Aix-Marseille University, CNRS, ICR, Marseille, France.
- Institut Universitaire de France, 75231, Paris, France
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2
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Wang H, Zhou Z, Long R, Prezhdo OV. Passivation of Hematite by a Semiconducting Overlayer Reduces Charge Recombination: An Insight from Nonadiabatic Molecular Dynamics. J Phys Chem Lett 2023; 14:879-887. [PMID: 36661401 DOI: 10.1021/acs.jpclett.2c03643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Hematite (α-Fe2O3) is a promising photoanode material for photoelectrochemical water splitting. Surface-passivating layers are effective in improving water oxidation kinetics; however, the passivation mechanism is not fully understood due to the complexity of interfacial reactions. Focusing on the Fe-terminated Fe2O3 (0001) surface that exhibits surface states in the band gap, we perform ab initio quantum dynamics simulations to study the effect of an α-Ga2O3 overlayer on charge recombination. The overlayer eliminates surface states and suppresses charge recombination 4-fold. This explains in part the observed cathodic shift in the onset potential for water oxidation. The increased charge carrier lifetime is an outcome of two factors, energy gap and electron-vibrational coupling, with a positive contribution from the former but a negative contribution from the latter. This work presents an advance in the atomistic time-domain understanding of the influence of surface passivation on charge recombination dynamics and provides guidance for designing novel α-Fe2O3 photoanodes.
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Affiliation(s)
- Hua Wang
- Department of Chemical Engineering, School of Water and Environment, Chang'an University, Xi'an710064, China
| | - Zhaohui Zhou
- Department of Chemical Engineering, School of Water and Environment, Chang'an University, Xi'an710064, China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing100875, China
| | - Oleg V Prezhdo
- Deparment of Chemistry, University of Southern California, Los Angeles, California90089, United States
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3
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Excited-state proton transfer reaction of a pyrenylurea derivative in the ionic liquid 1-ethyl-3-methylimidazolium acetate. Chem Phys Lett 2023. [DOI: 10.1016/j.cplett.2023.140342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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4
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Khelladi I, Springborg M, Rahmouni A, Chadli R, Sekkal-Rahal M. Theoretical Study on Non-Linear Optics Properties of Polycyclic Aromatic Hydrocarbons and the Effect of Their Intercalation with Carbon Nanotubes. Molecules 2022; 28:110. [PMID: 36615304 PMCID: PMC9822052 DOI: 10.3390/molecules28010110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 12/17/2022] [Accepted: 12/21/2022] [Indexed: 12/24/2022] Open
Abstract
Results of a theoretical study devoted to comparing NLO (non-linear optics) responses of derivatives of tetracene, isochrysene, and pyrene are reported. The static hyperpolarizability β, the dipole moment μ, the HOMO and LUMO orbitals, and their energy gap were calculated using the CAM-B3LYP density functional combined with the cc-pVDZ basis set. The para-disubstituted NO2-tetracene-N(CH3)2 has the highest NLO response, which is related to a large intramolecular charge transfer. Adding vinyl groups to the para-disubstituted NO2-tetracene-N(CH3)2 results in an increase in the NLO responses. We further investigated the effect of the intercalation of various push-pull molecules inside an armchair single-walled carbon nanotube. The intercalation leads to increased NLO responses, something that depends critically on the position of the guest molecule and/or on functionalization of the nanotube by donor and attractor groups.
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Affiliation(s)
- Imane Khelladi
- Laboratoire de Chimie Théorique de Bio- et Nanosystemes, Faculty of Exact Sciences, University Djillali Liabes of Sidi Bel-Abbes, B.P. 89, Sidi Bel Abbes 22000, Algeria
- Modeling and Computational Methods Laboratory, University of Saida, B.P. 148, Cité En-Nasr, Route de Mascara, 2002, Saida 20000, Algeria
| | - Michael Springborg
- Laboratory of Theoretical Chemistry, Department of Chemistry, Namur Institute of Structured Matter (NISM), University of Namur, Rue de Bruxelles 61, 5000 Namur, Belgium
| | - Ali Rahmouni
- Modeling and Computational Methods Laboratory, University of Saida, B.P. 148, Cité En-Nasr, Route de Mascara, 2002, Saida 20000, Algeria
| | - Redouane Chadli
- Laboratoire de Chimie Théorique de Bio- et Nanosystemes, Faculty of Exact Sciences, University Djillali Liabes of Sidi Bel-Abbes, B.P. 89, Sidi Bel Abbes 22000, Algeria
| | - Majda Sekkal-Rahal
- Laboratoire de Chimie Théorique de Bio- et Nanosystemes, Faculty of Exact Sciences, University Djillali Liabes of Sidi Bel-Abbes, B.P. 89, Sidi Bel Abbes 22000, Algeria
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5
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Cheng C, Zhu Y, Fang WH, Long R, Prezhdo OV. CO Adsorbate Promotes Polaron Photoactivity on the Reduced Rutile TiO 2(110) Surface. JACS AU 2022; 2:234-245. [PMID: 35098240 PMCID: PMC8790733 DOI: 10.1021/jacsau.1c00508] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Indexed: 06/14/2023]
Abstract
Polarons play a major role in determining the chemical properties of transition-metal oxides. Recent experiments show that adsorbates can attract inner polarons to surface sites. These findings require an atomistic understanding of the adsorbate influence on polaron dynamics and lifetime. We consider reduced rutile TiO2(110) with an oxygen vacancy as a prototypical surface and a CO molecule as a classic probe and perform ab initio adiabatic molecular dynamics, time-domain density functional theory, and nonadiabatic molecular dynamics simulations. The simulations show that subsurface polarons have little influence on CO adsorption and CO can desorb easily. On the contrary, surface polarons strongly enhance CO adsorption. At the same time, the adsorbed CO attracts polarons to the surface, allowing them to participate in catalytic processes with CO. The CO interaction with polarons changes their orbital origin, suppresses polaron hopping, and stabilizes them at surface sites. Partial delocalization of polarons onto CO decouples them from free holes, decreasing the nonadiabatic coupling and shortening the quantum coherence time, thereby reducing charge recombination. The calculations demonstrate that CO prefers to adsorb at the next-nearest-neighbor five-coordinated Ti3+ surface electron polaron sites. The reported results provide a fundamental understanding of the influence of electron polarons on the initial stage of reactant adsorption and the effect of the adsorbate-polaron interaction on the polaron dynamics and lifetime. The study demonstrates how charge and polaron properties can be controlled by adsorbed species, allowing one to design high-performance transition-metal oxide catalysts.
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Affiliation(s)
- Cheng Cheng
- College
of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry
of Ministry of Education, Beijing Normal
University, Beijing 100875, P.R. China
| | - Yonghao Zhu
- College
of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry
of Ministry of Education, Beijing Normal
University, Beijing 100875, P.R. China
| | - Wei-Hai Fang
- College
of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry
of Ministry of Education, Beijing Normal
University, Beijing 100875, P.R. China
| | - Run Long
- College
of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry
of Ministry of Education, Beijing Normal
University, Beijing 100875, P.R. China
| | - Oleg V. Prezhdo
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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6
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Wu Y, Prezhdo N, Chu W. Increasing Efficiency of Nonadiabatic Molecular Dynamics by Hamiltonian Interpolation with Kernel Ridge Regression. J Phys Chem A 2021; 125:9191-9200. [PMID: 34636570 DOI: 10.1021/acs.jpca.1c05105] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nonadiabatic (NA) molecular dynamics (MD) goes beyond the adiabatic Born-Oppenheimer approximation to account for transitions between electronic states. Such processes are common in molecules and materials used in solar energy, optoelectronics, sensing, and many other fields. NA-MD simulations are much more expensive compared to adiabatic MD due to the need to compute excited state properties and NA couplings (NACs). Similarly, application of machine learning (ML) to NA-MD is more challenging compared with adiabatic MD. We develop an NA-MD simulation strategy in which an adiabatic MD trajectory, which can be generated with a ML force field, is used to sample excitation energies and NACs for a small fraction of geometries, while the properties for the remaining geometries are interpolated with kernel ridge regression (KRR). This ML strategy allows for one to perform NA-MD under the classical path approximation, increasing the computational efficiency by over an order of magnitude. Compared to neural networks, KRR requires little parameter tuning, saving efforts on model building. The developed strategy is demonstrated with two metal halide perovskites that exhibit complicated MD and are actively studied for various applications.
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Affiliation(s)
- Yifan Wu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Natalie Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Weibin Chu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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7
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Wu Y, Chu W, Vasenko AS, Prezhdo OV. Common Defects Accelerate Charge Carrier Recombination in CsSnI 3 without Creating Mid-Gap States. J Phys Chem Lett 2021; 12:8699-8705. [PMID: 34472876 DOI: 10.1021/acs.jpclett.1c02443] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Lead-free metal halide perovskites are environmentally friendly and have favorable electro-optical properties; however, their efficiencies are significantly below the theoretical limit. Using ab initio nonadiabatic molecular dynamics, we show that common intrinsic defects accelerate nonradiative charge recombination in CsSnI3 without creating midgap traps. This is in contrast to Pb-based perovskites, in which many defects have little influence on and even prolong carrier lifetimes. Sn-related defects, such as Sn vacancies and replacement of Sn with Cs are most detrimental, since Sn removal breaks the largest number of bonds and strongly perturbs the Sn-I lattice that supports the carriers. The defects increase the nonadiabatic electron-vibrational coupling and interact strongly with free carrier states. Point defects associated with I atoms are less detrimental, and therefore, CsSnI3 synthesis should be performed in Sn rich conditions. The study provides an atomistic rationalization of why lead-free CsSnI3 exhibits lower photovoltaic efficiency compared to some lead-based perovskites.
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Affiliation(s)
- Yifan Wu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Weibin Chu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Andrey S Vasenko
- HSE University, 101000 Moscow, Russia
- I.E. Tamm Department of Theoretical Physics, P.N. Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow, Russia
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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8
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Mangan SM, Zhou G, Chu W, Prezhdo OV. Dependence between Structural and Electronic Properties of CsPbI 3: Unsupervised Machine Learning of Nonadiabatic Molecular Dynamics. J Phys Chem Lett 2021; 12:8672-8678. [PMID: 34472856 DOI: 10.1021/acs.jpclett.1c02361] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Using unsupervised machine learning on the trajectories from a nonadiabatic molecular dynamics simulation with time-dependent Kohn-Sham density functional theory, we elucidated the structural parameters with the largest influence on nonradiative recombination of charge carriers in CsPbI3, which forms the basis for solar energy and optoelectronic applications. The I-I-I angles between PbI6 octahedra, followed by the Cs-I distance, have the strongest impact on the bandgap and the nonadiabatic coupling. The importance of the Cs-I distance is unexpected, because Cs does not contribute to electron and hole wave functions. The nonadiabatic coupling is most influenced by static properties, which is also surprising, given its explicit dependence on atomic velocities.
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Affiliation(s)
- Spencer M Mangan
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089, United States
| | - Guoqing Zhou
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
| | - Weibin Chu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Oleg V Prezhdo
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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9
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Wang B, Chu W, Tkatchenko A, Prezhdo OV. Interpolating Nonadiabatic Molecular Dynamics Hamiltonian with Artificial Neural Networks. J Phys Chem Lett 2021; 12:6070-6077. [PMID: 34170705 DOI: 10.1021/acs.jpclett.1c01645] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Nonadiabatic (NA) molecular dynamics (MD) allows one to study far-from-equilibrium processes involving excited electronic states coupled to atomic motions. While NAMD involves expensive calculations of excitation energies and NA couplings (NACs), ground-state properties require much less effort and can be obtained with machine learning (ML) at a fraction of the ab initio cost. Application of ML to excited states and NACs is more challenging, due to costly reference methods, many states, and complex geometry dependence. We developed a NAMD methodology that avoids time extrapolation of excitation energies and NACs. Instead, under the classical path approximation that employs a precomputed ground-state trajectory, we use a small fraction (2%) of the geometries to train neural networks and obtain excited-state energies and NACs for the remaining 98% of the geometries by interpolation. Demonstrated with metal halide perovskites that exhibit complex MD, the method provides nearly two orders of computational savings while generating accurate NAMD results.
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Affiliation(s)
- Bipeng Wang
- Department of Chemical Engineering, University of Southern California, Los Angeles, California 90089, United States
| | - Weibin Chu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Alexandre Tkatchenko
- Department of Physics and Materials Science, University of Luxembourg, L-1511 Luxembourg, Luxembourg
| | - Oleg V Prezhdo
- Department of Chemical Engineering, University of Southern California, Los Angeles, California 90089, United States
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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10
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Qiao L, Fang WH, Long R, Prezhdo OV. Elimination of Charge Recombination Centers in Metal Halide Perovskites by Strain. J Am Chem Soc 2021; 143:9982-9990. [PMID: 34155882 DOI: 10.1021/jacs.1c04442] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Metal halide perovskites exhibit enhanced photoluminescence and long-lived carriers in experiments under strain. Using ab initio nonadiabatic molecular dynamics, we demonstrate that compressive and tensile strain can eliminate charge recombination centers created by defect states, by shifting traps from bandgap into bands. A compressive strain enhances coupling of Pb-s and I-p orbitals, pushes the valence band (VB) up in energy, and moves the trap state due to iodine interstitial (Ii) into the VB. The strain distorts the system and breaks the I-dimer responsible for the Ii trap. A tensile strain increases Pb-Pb distance, weakens overlap of Pb-p orbitals, and pushes the conduction band (CB) down in energy. The trap state created by replacement of iodine with methylammonium (MAI) is moved into the CB. Application of strain to the defective systems not only eliminates midgap traps but also creates moderate disorder that reduces overlap of electron and hole wave functions, activates phonon modes accelerating coherence loss within the electronic subsystem, and extends carrier lifetimes even beyond those in pristine MAPbI3. Our investigation rationalizes the high performance of perovskites solar cells under strain and reveals how strain passivates Ii and MAI defects in MAPbI3, providing a new nonchemical strategy for defect control and engineering.
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Affiliation(s)
- Lu Qiao
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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11
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Cheng C, Fang WH, Long R, Prezhdo OV. Water Splitting with a Single-Atom Cu/TiO 2 Photocatalyst: Atomistic Origin of High Efficiency and Proposed Enhancement by Spin Selection. JACS AU 2021; 1:550-559. [PMID: 34467318 PMCID: PMC8395698 DOI: 10.1021/jacsau.1c00004] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Indexed: 05/26/2023]
Abstract
Anatase TiO2 is an intensely investigated photocatalytic material due to its abundance and chemical stability. However, it suffers from weak light harvesting and low photocatalytic efficiency. Experiments show that light absorption and photocatalytic properties can be enhanced simultaneously by TiO2 doping with well-dispersed Cu atoms, forming a single-atom catalyst (Cu/TiO2) that can be used for solar water splitting and other applications. By performing ab initio nonadiabatic molecular dynamics simulations, we demonstrate that Cu/TiO2 is inactive before light irradiation due to rapid electron-hole recombination via both shallow and deep traps. Surprisingly, the shallow trap is more detrimental to the Cu/TiO2 performance than the deep trap because it couples better to free carriers. After light irradiation, leading to electron transfer and Cu/TiO2 protonation, the shallow trap is eliminated, and a local distortion around the Cu atom stabilizes the deep trap state on the Cu d-orbital, decoupling it from free charges and giving rise to high photocatalytic hydrogen generation activity. We further demonstrate that the photocatalytic performance of Cu/TiO2 can be enhanced by spin selection, achievable experimentally via optical intersite spin transfer or chiral semiconductor coating. Both H adsorption and spin selection enhance charge carrier lifetimes by an order of magnitude. The spin selection mechanism does not require formation of the H species, which necessitates concurrent sources of electrons and protons and which is intrinsically unstable because water splitting involves frequent proton shuffling. Our results rationalize the experimental observations at the atomistic level, provide mechanistic insights into operation of single atom photocatalysis, and demonstrate that spin selection can be used to develop advanced and efficient systems for solar energy conversion.
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Affiliation(s)
- Cheng Cheng
- College
of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry
of Ministry of Education, Beijing Normal
University, Beijing 100875, P.R. China
| | - Wei-Hai Fang
- College
of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry
of Ministry of Education, Beijing Normal
University, Beijing 100875, P.R. China
| | - Run Long
- College
of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry
of Ministry of Education, Beijing Normal
University, Beijing 100875, P.R. China
| | - Oleg V. Prezhdo
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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12
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Shi R, Vasenko AS, Long R, Prezhdo OV. Edge Influence on Charge Carrier Localization and Lifetime in CH 3NH 3PbBr 3 Perovskite: Ab Initio Quantum Dynamics Simulation. J Phys Chem Lett 2020; 11:9100-9109. [PMID: 33048554 DOI: 10.1021/acs.jpclett.0c02800] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The distribution of charge carriers in metal halide perovskites draws strong interest from the solar cell community, with experiments demonstrating that edges of various microstructures can improve material performance. This is rather surprising because edges and grain boundaries are often viewed as the main source of charge traps. We demonstrate by ab initio quantum dynamics simulations that edges of the CH3NH3PbBr3 perovskite create shallow trap states that mix well with the valence and conduction bands of the bulk and therefore support mobile charge carriers. Charges are steered to the edges energetically, facilitating dissociation of photo-generated excitons into free carriers. The edge-driven charge separation extends carrier lifetimes because of decreased overlap of the electron and hole wave functions, which leads to reduction of the nonadiabatic coupling responsible for nonradiative electron-hole recombination. Reduction of spatial symmetry near the edges activates additional vibrational modes that accelerate coherence loss within the electronic subsystem, further extending carrier lifetimes. Enhanced atomic motions at edges increase fluctuations of edge energy levels, enhancing mixing with band states and improving charge mobility. The simulations contribute to the atomistic understanding of the unusual properties of metal halide perovskites, generating the fundamental knowledge needed to design high-performance optoelectronic devices.
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Affiliation(s)
- Ran Shi
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Andrey S Vasenko
- National Research University Higher School of Economics, 101000 Moscow, Russia
- I.E. Tamm Department of Theoretical Physics, P.N. Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow, Russia
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Oleg V Prezhdo
- Departments of Chemistry, and Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
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13
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Agrawal S, Lin W, Prezhdo OV, Trivedi DJ. Ab initio quantum dynamics of charge carriers in graphitic carbon nitride nanosheets. J Chem Phys 2020; 153:054701. [PMID: 32770911 DOI: 10.1063/5.0010628] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Graphitic carbon nitride (g-C3N4), a metal-free and visible light responsive photocatalyst, has garnered much attention due to its wide range of applications. In order to elucidate the role of dimensionality on the properties of photo-generated charge carriers, we apply nonadiabatic (NA) molecular dynamics combined with time-domain density functional theory to investigate nonradiative relaxation of hot electrons and holes, and electron-hole recombination in monolayer and bulk g-C3N4. The nonradiative charge recombination occurs on a nanosecond timescale and is faster in bulk than the nanosheet, in agreement with the experiment. The difference arises due to the smaller energy gap and participation of additional vibrations in the bulk system. The long carrier lifetimes are favored by small NA coupling and rapid phonon-induced loss of quantum coherence between the excited and ground electronic states. Decoherence is fast because g-C3N4 is soft and undergoes large scale vibrations. The NA coupling is small since electrons and holes are localized on different atoms, and the electron-hole overlap is relatively small. Phonon-driven relaxation of hot electrons and holes takes 100-200 fs and is slightly slower at higher initial energies due to participation of fewer vibrational modes. This feature of two-dimensional g-C3N4 contrasts traditional three-dimensional semiconductors, which exhibit faster relaxation at higher energies due to larger density of states, and can be used to extract hot carriers to perform useful functions. The ab initio quantum dynamics simulations present a comprehensive picture of the photo-induced charge carrier dynamics in g-C3N4, guiding design of photovoltaic and photocatalytic devices.
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Affiliation(s)
- Sraddha Agrawal
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Wei Lin
- State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou 350108, People's Republic of China
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Dhara J Trivedi
- Department of Physics, Clarkson University, Potsdam, New York 13699, USA
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14
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He J, Fang WH, Long R, Prezhdo OV. Why Oxygen Increases Carrier Lifetimes but Accelerates Degradation of CH3NH3PbI3 under Light Irradiation: Time-Domain Ab Initio Analysis. J Am Chem Soc 2020; 142:14664-14673. [DOI: 10.1021/jacs.0c06769] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Jinlu He
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
| | - Oleg V. Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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15
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Wei Y, Tokina MV, Benderskii AV, Zhou Z, Long R, Prezhdo OV. Quantum dynamics origin of high photocatalytic activity of mixed-phase anatase/rutile TiO2. J Chem Phys 2020; 153:044706. [DOI: 10.1063/5.0014179] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Yaqing Wei
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People’s Republic of China
| | - Marina V. Tokina
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Alexander V. Benderskii
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Zhaohui Zhou
- Chemical Engineering and Technology, School of Environmental Science and Engineering, Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region, Ministry of Education, Chang’an University, Xi’an 710064, China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People’s Republic of China
| | - Oleg V. Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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16
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He J, Casanova D, Fang WH, Long R, Prezhdo OV. MAI Termination Favors Efficient Hole Extraction and Slow Charge Recombination at the MAPbI 3/CuSCN Heterojunction. J Phys Chem Lett 2020; 11:4481-4489. [PMID: 32423207 DOI: 10.1021/acs.jpclett.0c01467] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Photoinduced charge separation is the key step determining the efficiency of photon-to-electron conversion in solar cells, while charge carrier lifetimes govern the overall solar cell performance. Experiments report that copper(I) thiocyanate (CuSCN) is a very promising hole extraction layer for perovskite solar cells. Using nonadiabatic molecular dynamics combined with ab initio time-domain density functional theory, we show that termination of CH3NH3PbI3 (MAPbI3) at MAPbI3/CuSCN heterojunctions has a strong influence on both charge separation and recombination. Both processes are favored by MAI termination, compared to PbI2 termination. Because the MAPbI3 valence band originates from iodine orbitals while the conduction band arises from Pb orbitals, MAI termination places holes close to CuSCN, favoring extraction, and creates an MAI barrier for recombination of electrons in MAPbI3 and holes in CuSCN. The opposite is true for PbI2 termination. The origin of these effects is attributed solely to the properties of the MAPbI3 surfaces, and therefore, the conclusions should apply to other hole-transporting materials and can be generalized to other perovskites. Importantly, the simulations show that the injected hole remains hot for several hundreds of femtoseconds, allowing it to escape the interfacial region and prevent formation of bound excitons. This study suggests that metal halide perovskites should be treated with an organic precursor, such as MAI, prior to the formation of their interfaces with hole-transporting materials. The reported results advance the fundamental understanding of the highly unusual properties of metal halide perovskites and provide specific guidelines for optimizing the performance of perovskite solar cells and other devices.
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Affiliation(s)
- Jinlu He
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
| | - David Casanova
- Donostia International Physics Center (DIPC), 20018 Donostia, Euskadi, Spain
- IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Euskadi, Spain
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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17
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Zhang Z, Qiao L, Mora-Perez C, Long R, Prezhdo OV. Pb dimerization greatly accelerates charge losses in MAPbI3: Time-domain ab initio analysis. J Chem Phys 2020; 152:064707. [DOI: 10.1063/1.5131342] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Zhaosheng Zhang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People’s Republic of China
| | - Lu Qiao
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People’s Republic of China
| | - Carlos Mora-Perez
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People’s Republic of China
| | - Oleg V. Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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18
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Yang Y, Fang WH, Benderskii A, Long R, Prezhdo OV. Strain Controls Charge Carrier Lifetimes in Monolayer WSe 2: Ab Initio Time Domain Analysis. J Phys Chem Lett 2019; 10:7732-7739. [PMID: 31755714 DOI: 10.1021/acs.jpclett.9b03105] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Mono- and few-layer transition metal dichalcogenides (TMDs) are among the most appealing candidates for electronic and optoelectronic devices. During synthesis, TMDs actively interact with substrates, which induce notable strain and influence significantly charge carriers in TMDs. By performing time-domain ab initio simulations on monolayer WSe2, we demonstrate that charge carrier lifetimes vary by a factor of 3 within a typical 1% strain range, the bandgap changes by 0.2 eV, and electron-phonon interactions vary by 60%. Fortuitously, the most common tensile strain extends the lifetimes. The changes arise because of modifications in interatomic interactions. Further, compared to the optimized structure, at ambient temperature the bandgap drops by 0.1 eV and fluctuates by 0.1 eV. WSe2 obeys linear response within 1% strain; however, further strain leads to nonlinear qualitative changes in WSe2 electronic properties. The conduction band is affected more strongly than the valence band. Charges couple to phonons within a 100-400 cm-1 frequency range, with the strongest coupling to in-plane and out-of-plane modes at 250 cm-1. The reported findings agree with the available experiments and should be generic to other 2D materials. The strain effects need to be considered during TMD synthesis and provide means to control and tune TMD properties for 2D device applications.
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Affiliation(s)
- Yating Yang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , P.R. China
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , P.R. China
| | - Alex Benderskii
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , P.R. China
| | - Oleg V Prezhdo
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
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19
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Zhou X, Tokina MV, Tomko JA, Braun JL, Hopkins PE, Prezhdo OV. Thin Ti adhesion layer breaks bottleneck to hot hole relaxation in Au films. J Chem Phys 2019; 150:184701. [DOI: 10.1063/1.5096901] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- Xin Zhou
- College of Environment and Chemical Engineering, Dalian University, Dalian 116622, People’s Republic of China
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Marina V. Tokina
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - John A. Tomko
- Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22903, USA
| | - Jeffrey L. Braun
- Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 22903, USA
| | - Patrick E. Hopkins
- Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22903, USA
- Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 22903, USA
- Department of Physics, University of Virginia, Charlottesville, Virginia 22903, USA
| | - Oleg V. Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, USA
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20
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He J, Fang WH, Long R, Prezhdo OV. Superoxide/Peroxide Chemistry Extends Charge Carriers’ Lifetime but Undermines Chemical Stability of CH3NH3PbI3 Exposed to Oxygen: Time-Domain ab Initio Analysis. J Am Chem Soc 2019; 141:5798-5807. [DOI: 10.1021/jacs.8b13392] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Jinlu He
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing, 100875, People’s Republic of China
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing, 100875, People’s Republic of China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing, 100875, People’s Republic of China
| | - Oleg V. Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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21
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Kar M, Rajbanshi B, Sarkar R, Pal S, Sarkar P. Periodically-ordered one and two dimensional CdTe QD superstructures: a path forward in photovoltaics. Phys Chem Chem Phys 2019; 21:19391-19402. [DOI: 10.1039/c9cp03529j] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
By using the state-of-the-art theoretical method, we herein explore the potentiality of covalently linked periodically-ordered 1D chain, 2D hexagonal and square ordered superstructures of CdTe QDs in photovoltaics.
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Affiliation(s)
- Moumita Kar
- Department of Chemistry
- Visva-Bharati University
- Santiniketan-731235
- India
| | - Biplab Rajbanshi
- Department of Chemistry
- Visva-Bharati University
- Santiniketan-731235
- India
| | - Ritabrata Sarkar
- Department of Chemistry
- University of Gour Banga
- Malda-732103
- India
| | - Sougata Pal
- Department of Chemistry
- University of Gour Banga
- Malda-732103
- India
| | - Pranab Sarkar
- Department of Chemistry
- Visva-Bharati University
- Santiniketan-731235
- India
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22
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Li W, Sun YY, Li L, Zhou Z, Tang J, Prezhdo OV. Control of Charge Recombination in Perovskites by Oxidation State of Halide Vacancy. J Am Chem Soc 2018; 140:15753-15763. [DOI: 10.1021/jacs.8b08448] [Citation(s) in RCA: 99] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Wei Li
- College of Science, Hunan Agricultural University, Changsha 410128, People’s Republic of China
| | - Yi-Yang Sun
- State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899, People’s Republic of China
| | - Linqiu Li
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Zhaohui Zhou
- Chemical Engineering and Technology, School of Environmental Science and Engineering, and Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region, Ministry of Education, Chang’an University, Xi’an 710064, People’s Republic of China
| | - Jianfeng Tang
- College of Science, Hunan Agricultural University, Changsha 410128, People’s Republic of China
| | - Oleg V. Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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23
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Sarkar R, Habib M, Pal S, Prezhdo OV. Ultrafast, asymmetric charge transfer and slow charge recombination in porphyrin/CNT composites demonstrated by time-domain atomistic simulation. NANOSCALE 2018; 10:12683-12694. [PMID: 29946626 DOI: 10.1039/c8nr02544d] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The versatile photochemical properties of porphyrin molecules make them excellent candidates for solar energy applications. Carbon nanotubes (CNTs) exhibit superior charge conductivity and have been combined with porphyrins to achieve efficient and ultrafast charge separation. Experiments show that the charge separated state lives less than 10 ps, which is too short for applications. Using real-time time-dependent tight binding density functional theory (DFTB) combined with non-adiabatic molecular dynamics (NAMD), we model photo-induced charge separation and recombination in two porphyrin/CNT composites. Having achieved excellent agreement with the experiment for the electron transfer from the porphyrins to the CNT, we demonstrate that hole transfer can be achieved upon CNT excitation, although in a less efficient way. By exciting the CNT one can extend light harvesting into lower energies of the solar spectrum and increase solar light conversion efficiency. We also show that the charge separated state can live over 1 ns. The two orders of magnitude difference from the experimental lifetime could arise due to the presence of defects or metallic tubes in the samples. The charge separated state is long-lived because the non-adiabatic electron-phonon coupling is very small, less than 1 meV, and the quantum coherence is short, 15-20 fs. The excited states in the isolated porphyrins and CNT live around 100 ps, in agreement with experiments as well. The porphyrin/CNT interaction occurs through the π-electron systems of the two species. The non-radiative relaxation is promoted by both high and low frequency phonons, with higher frequency phonons playing more important roles in electron relaxation than in hole relaxation. Low frequency phonons contribute significantly to the decay of the charge separated state, because they modulate the relative positions of the porphyrins and the CNT. The time-domain atomistic simulations provide a detailed understanding of the charge separation and recombination mechanisms, and generate valuable guidelines for the optimization of photovoltaic efficiency in modern nanoscale materials.
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Affiliation(s)
- Ritabrata Sarkar
- Department of Chemistry, University of Gour Banga, Malda, 732103, India.
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24
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Righetto M, Privitera A, Carraro F, Bolzonello L, Ferrante C, Franco L, Bozio R. Engineering interactions in QDs-PCBM blends: a surface chemistry approach. NANOSCALE 2018; 10:11913-11922. [PMID: 29901055 DOI: 10.1039/c8nr03520b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Here we present a comprehensive study on the photophysics of QDs-fullerene blends, aiming to elucidate the impact of ligands on the extraction of carriers from QDs. We investigated how three different ligands (oleylamine, octadecanethiol and propanethiol) influence the dynamics of charge generation, separation, and recombination in blends of CdSe/CdS core/shell QDs and PCBM. We accessed each relevant process directly by combining the results from both optical and magnetic spectroscopies. Transient absorption measurements revealed a faster interaction dynamics in thiol-capped ligands. Through phenomenological modeling of the interaction processes, i.e., energy transfer and electron transfer, we estimated the suppression of exciton migration and the enhancement of electron transfer processes when alkyl-thiols are employed as ligands. Contextually, we report the profound impact of the ligands' alkyl chain length, leading to strengthened interactions with PCBM acceptors. Quantitatively, we measured a 10-fold increase in the electron transfer rate when oleylamine ligands were exchanged with propanethiol ligands. EPR spectroscopy gave access to subtle details regarding both the enhanced charge generation and lower binding energy of charge-transfer states in blends compared to PCBM alone. Moreover, through pulsed EPR techniques, we inferred the localization of deep electron traps in localized sites close to QDs in the blends. Therefore, our thorough characterization evidenced the essential role of ligands in determining QD interactions. We believe that these discoveries will contribute to the efficient incorporation of QDs in existing organic PV technologies.
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Affiliation(s)
- Marcello Righetto
- Department of Chemical Science and U.R. INSTM, University of Padova, Via Marzolo 1, I-35131, Padova, Italy.
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25
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Li L, Long R, Prezhdo OV. Why Chemical Vapor Deposition Grown MoS 2 Samples Outperform Physical Vapor Deposition Samples: Time-Domain ab Initio Analysis. NANO LETTERS 2018; 18:4008-4014. [PMID: 29772904 DOI: 10.1021/acs.nanolett.8b01501] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Two-dimensional transition metal dichalcogenides (TMDs) have drawn strong attention due to their unique properties and diverse applications. However, TMD performance depends strongly on material quality and defect morphology. Experiments show that samples grown by chemical vapor deposition (CVD) outperform those obtained by physical vapor deposition (PVD). Experiments also show that CVD samples exhibit vacancy defects, while antisite defects are frequently observed in PVD samples. Our time-domain ab initio study demonstrates that both antisites and vacancies accelerate trapping and nonradiative recombination of charge carriers, but antisites are much more detrimental than vacancies. Antisites create deep traps for both electrons and holes, reducing energy gaps for recombination, while vacancies trap primarily holes. Antisites also perturb band-edge states, creating significant overlap with the trap states. In comparison, vacancy defects overlap much less with the band-edge states. Finally, antisites can create pairs of electron and hole traps close to the Fermi energy, allowing trapping by thermal activation from the ground state and strongly contributing to charge scattering. As a result, antisites accelerate charge recombination by more than a factor of 8, while vacancies enhance the recombination by less than a factor of 2. Our simulations demonstrate a general principle that missing atoms are significantly more benign than misplaced atoms, such as antisites and adatoms. The study rationalizes the existing experimental data, provides theoretical insights into the diverse behavior of different classes of defects, and generates guidelines for defect engineering to achieve high-performance electronic, optoelectronic, and solar-cell devices.
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Affiliation(s)
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , PR China
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26
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He J, Vasenko AS, Long R, Prezhdo OV. Halide Composition Controls Electron-Hole Recombination in Cesium-Lead Halide Perovskite Quantum Dots: A Time Domain Ab Initio Study. J Phys Chem Lett 2018; 9:1872-1879. [PMID: 29595268 DOI: 10.1021/acs.jpclett.8b00446] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We demonstrate that halide content strongly affects nonradiative electron-hole recombination in all-inorganic perovskite quantum dots (QDs). Using time domain density functional theory and nonadiabatic molecular dynamics, we show that replacing half of the bromines with iodines in a CsPbBr3 QD extends the charge carrier lifetime by a factor of 5, while complete replacement extends the lifetime by a factor of 8. Doping with iodines decreases the nonadiabatic charge-phonon coupling because iodines are heavier and slower than bromines and because the overlap between the electron and hole wave functions is reduced. In general, the nonradiative electron-hole recombination proceeds slowly, on a nanosecond time scale, due to small sub-1 meV nonadiabatic coupling and short sub-10 fs coherence times. The obtained recombination times and their dependence on the halogen content show excellent agreement with experiments. Our study suggests that the power conversion efficiencies of solar cells can be controlled by changing the halide composition in all-inorganic perovskite QDs.
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Affiliation(s)
- Jinlu He
- College of Chemistry , Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing 100875 , People's Republic of China
| | - Andrey S Vasenko
- National Research University Higher School of Economics , 101000 Moscow , Russia
| | - Run Long
- College of Chemistry , Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing 100875 , People's Republic of China
| | - Oleg V Prezhdo
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
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27
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Zhang Z, Fang WH, Tokina MV, Long R, Prezhdo OV. Rapid Decoherence Suppresses Charge Recombination in Multi-Layer 2D Halide Perovskites: Time-Domain Ab Initio Analysis. NANO LETTERS 2018. [PMID: 29533630 DOI: 10.1021/acs.nanolett.8b00035] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Two-dimensional (2D) Ruddlesden-Popper halide perovskites are appealing candidates for optoelectronics and photovoltaics. Nonradiative electron-hole recombination constitutes a major pathway for charge and energy losses in these materials. Surprisingly, experimental recombination is slower in multilayers than a monolayer, even though multilayer systems have smaller energy gaps and higher frequency phonons that should accelerate the recombination. Focusing on (BA)2(MA) n-1Pb nI3 n+1 with n = 1 and 3, BA = CH3(CH2)3NH3, and MA = CH3NH3, we show that it is the enhancement of elastic electron-phonon scattering that suppresses charge recombination for n = 3, by causing rapid loss of electronic coherence. The scattering is enhanced in the multilayer 2D perovskites because, in contrast to the monolayer, they contain MA cations embedded into the inorganic Pb-I lattice. Although MAs do not contribute directly to electron and hole wave functions, they perturb the Pb-I lattice and create strong electric fields that interact with the charges. The rapid loss of coherence explains long excited state lifetimes that extend into nanoseconds. Both electron-hole recombination and coherence times show excellent agreement with the corresponding lifetime and line width measurements. The simulations rationalize the observed dependence of excited state lifetime in 2D layered halide perovskites on layer thickness and advance our understanding of the atomistic mechanisms underlying charge-phonon dynamics in nanoscale materials.
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Affiliation(s)
- Zhaosheng Zhang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing , 100875 , P. R. China
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing , 100875 , P. R. China
| | - Marina V Tokina
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing , 100875 , P. R. China
| | - Oleg V Prezhdo
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
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28
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Liu L, Fang WH, Long R, Prezhdo OV. Lewis Base Passivation of Hybrid Halide Perovskites Slows Electron-Hole Recombination: Time-Domain Ab Initio Analysis. J Phys Chem Lett 2018; 9:1164-1171. [PMID: 29461842 DOI: 10.1021/acs.jpclett.8b00177] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Nonradiative electron-hole recombination plays a key role in determining photon conversion efficiencies in solar cells. Experiments demonstrate significant reduction in the recombination rate upon passivation of methylammonium lead iodide perovskite with Lewis base molecules. Using nonadiabatic molecular dynamics combined with time-domain density functional theory, we find that the nonradiative charge recombination is decelerated by an order of magnitude upon adsorption of the molecules. Thiophene acts by the traditional passivation mechanism, forcing electron density away from the surface. In contrast, pyridine localizes the electron at the surface while leaving it energetically near the conduction band edge. This is because pyridine creates a stronger coordinative bond with a lead atom of the perovskite and has a lower energy unoccupied orbital compared with thiophene due to the more electronegative nitrogen atom relative to thiophene's sulfur. Both molecules reduce two-fold the nonadiabatic coupling and electronic coherence time. A broad range of vibrational modes couple to the electronic subsystem, arising from inorganic and organic components. The simulations reveal the atomistic mechanisms underlying the enhancement of the excited-state lifetime achieved by the perovskite passivation, rationalize the experimental results, and advance our understanding of charge-phonon dynamics in perovskite solar cells.
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Affiliation(s)
- Lihong Liu
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China
| | - Wei-Hai Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China
| | - Run Long
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
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29
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Nijamudheen A, Akimov AV. Criticality of Symmetry in Rational Design of Chalcogenide Perovskites. J Phys Chem Lett 2018; 9:248-257. [PMID: 29275636 DOI: 10.1021/acs.jpclett.7b02589] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Chalcogenide perovskites constitute an emerging class of promising photovoltaic materials that are stable and less toxic than popular lead-halide perovskites. Transition-metal and chalcogenide doping are the possible strategies for improving the photovoltaic properties of these materials via the band gap engineering. At the same time, doping can facilitate nonradiative charge-carrier recombination in these materials, adversely affecting their photovoltaic properties. We report a systematic study of electronic structure and nonadiabatic dynamics in transition-metal- and chalcogenide-doped barium-zirconium-sulfide-based perovskites. The potential of these doping strategies to modulate the performance of photovoltaic materials is explored. Through the detailed analysis of the factors affecting the dynamics, we illustrate how symmetry (both structural and orbital) and decoherence can be critical to furnishing the most favorable properties. The noted factors of symmetry and decoherence may provide new rational design principles for efficient photovoltaics.
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Affiliation(s)
- A Nijamudheen
- Department of Chemistry, University at Buffalo, The State University of New York , Buffalo, New York 14260-3000, United States
| | - Alexey V Akimov
- Department of Chemistry, University at Buffalo, The State University of New York , Buffalo, New York 14260-3000, United States
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30
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Zhou X, Jankowska J, Li L, Giri A, Hopkins PE, Prezhdo OV. Strong Influence of Ti Adhesion Layer on Electron-Phonon Relaxation in Thin Gold Films: Ab Initio Nonadiabatic Molecular Dynamics. ACS APPLIED MATERIALS & INTERFACES 2017; 9:43343-43351. [PMID: 29135220 DOI: 10.1021/acsami.7b12535] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Electron-phonon relaxation in thin metal films is an important consideration for many ultrasmall devices and ultrafast applications. Recent time-resolved experiments demonstrate a significant, more than a factor of five, increase in the electron-phonon coupling and acceleration in the electron-phonon relaxation rate when a narrow Ti adhesion layer is introduced between an Au film and a nonmetal substrate. Using nonadiabatic molecular dynamics combined with real-time time-dependent density functional theory, we identify the reasons that give rise to this strong effect. First, the Ti layer greatly enhances the density of states (DOS) in the energy region starting at 1 eV below the Fermi level and extending several electronvolts above it. Second, Ti atoms are four times lighter than Au atoms and therefore generate larger nonadiabatic (NA) electron-phonon coupling. Because the transition rates depend on coupling and DOS, both the factors accelerate the dynamics. Showing good agreement with the experiments, the time-domain atomistic simulations provide a detailed mechanistic understanding of the electron-phonon relaxation dynamics in thin gold films and related nanomaterials.
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Affiliation(s)
- Xin Zhou
- College of Environment and Chemical Engineering, Dalian University , Dalian 116622, P. R. China
| | - Joanna Jankowska
- Institute of Physics, Polish Academy of Sciences , 02-668 Warsaw, Poland
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31
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Li L, Long R, Bertolini T, Prezhdo OV. Sulfur Adatom and Vacancy Accelerate Charge Recombination in MoS 2 but by Different Mechanisms: Time-Domain Ab Initio Analysis. NANO LETTERS 2017; 17:7962-7967. [PMID: 29172545 DOI: 10.1021/acs.nanolett.7b04374] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Two-dimensional transition metal dichalcogenides (TMDs) have appeared on the horizon of materials science and solid-state physics due to their unique properties and diverse applications. TMD performance depends strongly on material quality and defect morphology. Calculations predict that sulfur adatom and vacancy are among the most energetically favorable defects in MoS2 with vacancies frequently observed during chemical vapor deposition. By performing ab initio quantum dynamics calculations we demonstrate that both adatom and vacancy accelerate nonradiative charge carrier recombination but this happens through different mechanisms. Surprisingly, holes never significantly populate the shallow trap state created by the sulfur adatom because the trap is strongly localized and decoupled from free charges. Charge recombination bypasses the hole trap. Instead, it occurs directly between free electron and hole. The recombination is faster than in pristine MoS2 because the adatom strongly perturbs the MoS2 layer, breaks its symmetry, and allows more phonon modes to couple to the electronic subsystem. In contrast, the sulfur vacancy accelerates charge recombination by the traditional mechanism involving charge trapping, followed by recombination. This is because the hole and electron traps created by the vacancy are much less localized than the hole trap created by the adatom. Because the sulfur adatom accelerates charge recombination by a factor of 7.9, compared to 1.7 due to vacancy, sulfur adatoms should be strongly avoided. The generated insights highlight the diverse behavior of different types of defects, reveal unexpected features, and provide the mechanistic understanding of charge dynamics needed for tailoring TMD properties and building high-performance devices.
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Affiliation(s)
- Linqiu Li
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing, 100875, People's Republic of China
| | - Thomas Bertolini
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
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Tkachenko NV. Photoinduced Charge Separation in Semiconductor-Quantum-Dot/Organic-Molecule Hybrids. CHEMPHOTOCHEM 2017. [DOI: 10.1002/cptc.201700161] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Nikolai V. Tkachenko
- Laboratory of Chemistry and Bioengineering; Tampere University of Technology; P.O.Box 541 33101 Tampere Finland
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Rajbanshi B, Kar M, Sarkar P, Sarkar P. Phosphorene quantum dot-fullerene nanocomposites for solar energy conversion: An unexplored inorganic-organic nanohybrid with novel photovoltaic properties. Chem Phys Lett 2017. [DOI: 10.1016/j.cplett.2017.07.033] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Wei Y, Li L, Fang W, Long R, Prezhdo OV. Weak Donor-Acceptor Interaction and Interface Polarization Define Photoexcitation Dynamics in the MoS 2/TiO 2 Composite: Time-Domain Ab Initio Simulation. NANO LETTERS 2017; 17:4038-4046. [PMID: 28586230 DOI: 10.1021/acs.nanolett.7b00167] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
To realize the full potential of transition metal dichalcogenides interfaced with bulk semiconductors for solar energy applications, fast photoinduced charge separation, and slow electron-hole recombination are needed. Using a combination of time-domain density functional theory with nonadiabatic molecular dynamics, we demonstrate that the key features of the electron transfer (ET), energy relaxation and electron-hole recombination in a MoS2-TiO2 system are governed by the weak van der Waals interfacial interaction and interface polarization. Electric fields formed at the interface allow charge separation to happen already during the photoexcitation process. Those electrons that still reside inside MoS2, transfer into TiO2 slowly and by the nonadiabatic mechanism, due to weak donor-acceptor coupling. The ET time depends on excitation energy, because the TiO2 state density grows with energy, increasing the nonadiabatic transfer rate, and because MoS2 sulfur atoms start to contribute to the photoexcited state at higher energies, increasing the coupling. The ET is slower than electron-phonon energy relaxation because the donor-acceptor coupling is weak, rationalizing the experimentally observed injection of primarily hot electrons. The weak van der Waals MoS2-TiO2 interaction ensures a long-lived charge separated state and a short electron-hole coherence time. The injection is promoted primarily by phonons within the 200-800 cm-1 range. Higher frequency modes are particularly important for the electron-hole recombinations, because they are able to accept large amounts of electronic energy. The predicted time scales for the forward and backward ET, and energy relaxation can be measured by time-resolved spectroscopies. The reported simulations generate a detailed time-domain atomistic description of the complex interplay of the charge and energy transfer processes at the MoS2/TiO2 interface that are of fundamental importance to photovoltaic and photocatalytic applications. The results suggest that even though the photogenerated charge-separated state is long-lived, the slower charge separation, compared to the electron-phonon energy relaxation, can present problems in practical applications.
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Affiliation(s)
- Yaqing Wei
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing, 100875, People's Republic of China
| | - Linqiu Li
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Weihai Fang
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing, 100875, People's Republic of China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing, 100875, People's Republic of China
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
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Long R, Prezhdo OV, Fang W. Nonadiabatic charge dynamics in novel solar cell materials. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2017. [DOI: 10.1002/wcms.1305] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education Beijing Normal University Beijing P.R. China
| | - Oleg V. Prezhdo
- Department of Chemistry University of Southern California Los Angeles CA USA
| | - Weihai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education Beijing Normal University Beijing P.R. China
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Long R, Casanova D, Fang WH, Prezhdo OV. Donor–Acceptor Interaction Determines the Mechanism of Photoinduced Electron Injection from Graphene Quantum Dots into TiO2: π-Stacking Supersedes Covalent Bonding. J Am Chem Soc 2017; 139:2619-2629. [DOI: 10.1021/jacs.6b09598] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing, 100875, P. R. China
| | - David Casanova
- Kimika Fakultatea,
Euskal Herriko Unibertsitatea and Donostia International Physics Center, 20018 Donostia, Euskadi, Spain
- IKERBASQUE, Basque
Foundation for Science, 48013 Bilbao, Euskadi, Spain
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing, 100875, P. R. China
| | - Oleg V. Prezhdo
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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Arvani M, Virkki K, Abou-Chahine F, Efimov A, Schramm A, Tkachenko NV, Lupo D. Photoinduced hole transfer in QD-phthalocyanine hybrids. Phys Chem Chem Phys 2016; 18:27414-27421. [PMID: 27722635 DOI: 10.1039/c6cp04374g] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A series of CdSe quantum dot (QD)-phthalocyanine (Pc) hybrids were synthesized and their photophysics was studied using steady state and time-resolved spectroscopic methods. Emission of QDs was progressively quenched upon increasing the concentration of Pc in the hybrids. A detailed transient absorption study of the hybrids revealed that the mechanism of quenching is charge separation, resulting in the formation of hybrids with negatively charged QDs and the Pc cation. Direct photo-excitation of Pc did not show any detectable interaction between the excited state of Pc and the QD to which it is attached. An explanation is proposed, based on the suggestion that the energy of the lowest unoccupied molecular orbital (LUMO) of Pc is lower than the lower edge of the QD conduction band, while the energy of the highest occupied molecular orbital (HOMO) of Pc is sufficiently higher than the high energy edge of the QD valence band (VB), thus permitting hole transfer from the QD VB to the Pc HOMO after photo-excitation of QDs.
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Affiliation(s)
- M Arvani
- Department of Electronics and Communications Engineering, Tampere University of Technology, 33720 Tampere, Finland.
| | - K Virkki
- Department of Chemistry and Bioengineering, Tampere University of Technology, 33720 Tampere, Finland.
| | - F Abou-Chahine
- Department of Chemistry and Bioengineering, Tampere University of Technology, 33720 Tampere, Finland.
| | - A Efimov
- Department of Chemistry and Bioengineering, Tampere University of Technology, 33720 Tampere, Finland.
| | - A Schramm
- Department of Electronics and Communications Engineering, Tampere University of Technology, 33720 Tampere, Finland.
| | - N V Tkachenko
- Department of Chemistry and Bioengineering, Tampere University of Technology, 33720 Tampere, Finland.
| | - D Lupo
- Department of Electronics and Communications Engineering, Tampere University of Technology, 33720 Tampere, Finland.
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Long R, Guo M, Liu L, Fang W. Nonradiative Relaxation of Photoexcited Black Phosphorus Is Reduced by Stacking with MoS2: A Time Domain ab Initio Study. J Phys Chem Lett 2016; 7:1830-1835. [PMID: 27132486 DOI: 10.1021/acs.jpclett.6b00757] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Black phosphorus (BP) is an appealing material for applications in electronics and optoelectronics because of its tunable direct band gap and high charge carrier mobility. For real optoelectronic device utilization, nonradiative electron-hole recombination should be slow because it constitutes a major pathway for charge and energy losses. Using time-domain density functional theory combined with nonadiabatic (NA) molecular dynamics, we show that nonradiative electron-hole recombination occurs within several tens of picoseconds in bilayer BP, agreeing well with experimental data. When a single layer of BP is stacked with monolayer MoS2, the recombination is reduced because of the increased band gap and reduced electron-phonon NA coupling compared to bilayer BP. The slow electron-phonon energy losses in BP-MoS2 van der Waals heterojunction relative to bilayer BP indicate that rationally stacking BP with other two-dimensional materials is an attractive route for designing novel and efficient photovoltaic materials.
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Affiliation(s)
- Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing, 100875, P. R. China
| | - Meng Guo
- Shandong Computer Science Center (National Supercomputer Center in Jinan) , Jinan, Shandong Province P. R. China , 250101
| | - Lihong Liu
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing, 100875, P. R. China
| | - Weihai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing, 100875, P. R. China
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Long R, Prezhdo OV. Quantum Coherence Facilitates Efficient Charge Separation at a MoS2/MoSe2 van der Waals Junction. NANO LETTERS 2016; 16:1996-2003. [PMID: 26882202 DOI: 10.1021/acs.nanolett.5b05264] [Citation(s) in RCA: 128] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Two-dimensional transition metal dichalcogenides (MX2, M = Mo, W; X = S, Se) hold great potential in optoelectronics and photovoltaics. To achieve efficient light-to-electricity conversion, electron-hole pairs must dissociate into free charges. Coulomb interaction in MX2 often exceeds the charge transfer driving force, leading one to expect inefficient charge separation at a MX2 heterojunction. Experiments defy the expectation. Using time-domain density functional theory and nonadiabatic (NA) molecular dynamics, we show that quantum coherence and donor-acceptor delocalization facilitate rapid charge transfer at a MoS2/MoSe2 interface. The delocalization is larger for electron than hole, resulting in longer coherence and faster transfer. Stronger NA coupling and higher acceptor state density accelerate electron transfer further. Both electron and hole transfers are subpicosecond, which is in agreement with experiments. The transfers are promoted primarily by the out-of-plane Mo-X modes of the acceptors. Lighter S atoms, compared to Se, create larger NA coupling for electrons than holes. The relatively slow relaxation of the "hot" hole suggests long-distance bandlike transport, observed in organic photovoltaics. The electron-hole recombination is notably longer across the MoS2/MoSe2 interface than in isolated MoS2 and MoSe2, favoring long-lived charge separation. The atomistic, time-domain studies provide valuable insights into excitation dynamics in two-dimensional transition metal dichalcogenides.
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Affiliation(s)
- Run Long
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing, 100875, People's Republic of China
- School of Physics and Complex and Adaptive Systems Lab, University College Dublin , Dublin 4, Ireland
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
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Long R, Prezhdo OV. Dopants Control Electron-Hole Recombination at Perovskite-TiO₂ Interfaces: Ab Initio Time-Domain Study. ACS NANO 2015; 9:11143-11155. [PMID: 26456384 DOI: 10.1021/acsnano.5b05843] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
TiO2 sensitized with organohalide perovskites gives rise to solar-to-electricity conversion efficiencies reaching close to 20%. Nonradiative electron-hole recombination across the perovskite/TiO2 interface constitutes a major pathway of energy losses, limiting quantum yield of the photoinduced charge. In order to establish the fundamental mechanisms of the energy losses and to propose practical means for controlling the interfacial electron-hole recombination, we applied ab initio nonadiabatic (NA) molecular dynamics to pristine and doped CH3NH3PbI3(100)/TiO2 anatase(001) interfaces. We show that doping by substitution of iodide with chlorine or bromine reduces charge recombination, while replacing lead with tin enhances the recombination. Generally, lighter and faster atoms increase the NA coupling. Since the dopants are lighter than the atoms they replace, one expects a priori that all three dopants should accelerate the recombination. We rationalize the unexpected behavior of chlorine and bromine by three effects. First, the Pb-Cl and Pb-Br bonds are shorter than the Pb-I bond. As a result, Cl and Br atoms are farther away from the TiO2 surface, decreasing the donor-acceptor coupling. In contrast, some iodines form chemical bonds with Ti atoms, increasing the coupling. Second, chlorine and bromine reduce the NA electron-vibrational coupling, because they contribute little to the electron and hole wave functions. Tin increases the coupling, since it is lighter than lead and contributes to the hole wave function. Third, higher frequency modes introduced by chlorine and bromine shorten quantum coherence, thereby decreasing the transition rate. The recombination occurs due to coupling of the electronic subsystem to low-frequency perovskite and TiO2 modes. The simulation shows excellent agreement with the available experimental data and advances our understanding of electronic and vibrational dynamics in perovskite solar cells. The study provides design principles for optimizing solar cell performance and increasing photon-to-electron conversion efficiency through creative choice of dopants.
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Affiliation(s)
- Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing, 100875, People's Republic of China
- School of Physics, Complex & Adaptive Systems Lab, University College Dublin , Dublin, Ireland
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
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Long R, Prezhdo OV. Time-Domain Ab Initio Analysis of Excitation Dynamics in a Quantum Dot/Polymer Hybrid: Atomistic Description Rationalizes Experiment. NANO LETTERS 2015; 15:4274-4281. [PMID: 26061416 DOI: 10.1021/nl5046268] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Hybrid organic/inorganic polymer/quantum dot (QD) solar cells are an attractive alternative to the traditional cells. The original, simple models postulate that one-dimensional polymers have continuous energy levels, while zero-dimensional QDs exhibit atom-like electronic structure. A realistic, atomistic viewpoint provides an alternative description. Electronic states in polymers are molecule-like: finite in size and discrete in energy. QDs are composed of many atoms and have high, bulk-like densities of states. We employ ab initio time-domain simulation to model the experimentally observed ultrafast photoinduced dynamics in a QD/polymer hybrid and show that an atomistic description is essential for understanding the time-resolved experimental data. Both electron and hole transfers across the interface exhibit subpicosecond time scales. The interfacial processes are fast due to strong electronic donor-acceptor, as evidenced by the densities of the photoexcited states which are delocalized between the donor and the acceptor. The nonadiabatic charge-phonon coupling is also strong, especially in the polymer, resulting in rapid energy losses. The electron transfer from the polymer is notably faster than the hole transfer from the QD, due to a significantly higher density of acceptor states. The stronger molecule-like electronic and charge-phonon coupling in the polymer rationalizes why the electron-hole recombination inside the polymer is several orders of magnitude faster than in the QD. As a result, experiments exhibit multiple transfer times for the long-lived hole inside the QD, ranging from subpicoseconds to nanoseconds. In contrast, transfer of the short-lived electron inside the polymer does not occur beyond the first picosecond. The energy lost by the hole on its transit into the polymer is accommodated by polymer's high-frequency vibrations. The energy lost by the electron injected into the QD is accommodated primarily by much lower-frequency collective and QD modes. The electron dynamics is exponential, whereas evolution of the injected hole through the low density manifold of states of the polymer is highly nonexponential. The time scale of the electron-hole recombination at the interface is intermediate between those in pristine polymer and QD and is closer to that in the polymer. The detailed atomistic insights into the photoinduced charge and energy dynamics at the polymer/QD interface provide valuable guidelines for optimization of solar light harvesting and photovoltaic efficiency in modern nanoscale materials.
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Affiliation(s)
| | - Oleg V Prezhdo
- §Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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Wang L, Long R, Prezhdo OV. Time-Domain Ab Initio Modeling of Photoinduced Dynamics at Nanoscale Interfaces. Annu Rev Phys Chem 2015; 66:549-79. [DOI: 10.1146/annurev-physchem-040214-121359] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Linjun Wang
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482;
- Department of Chemistry, University of Rochester, Rochester, New York 14627
| | - Run Long
- School of Physics and Complex & Adaptive Systems Laboratory, University College Dublin, Belfield, Dublin 4, Ireland
| | - Oleg V. Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482;
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Ding TX, Olshansky JH, Leone SR, Alivisatos AP. Efficiency of Hole Transfer from Photoexcited Quantum Dots to Covalently Linked Molecular Species. J Am Chem Soc 2015; 137:2021-9. [DOI: 10.1021/ja512278a] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Tina X. Ding
- Kavli Energy Nanosciences Institute, Berkeley, California 94720, United States
| | - Jacob H. Olshansky
- Kavli Energy Nanosciences Institute, Berkeley, California 94720, United States
| | | | - A. Paul Alivisatos
- Kavli Energy Nanosciences Institute, Berkeley, California 94720, United States
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Chaban VV, Fileti EE. Strong electronic polarization of the C60 fullerene by imidazolium-based ionic liquids: accurate insights from Born–Oppenheimer molecular dynamic simulations. Phys Chem Chem Phys 2015; 17:15739-45. [DOI: 10.1039/c5cp00350d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Fullerenes are known to be polarizable due to their strained carbon–carbon bonds and high surface curvature.
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Affiliation(s)
- Vitaly V. Chaban
- Instituto de Ciência e Tecnologia
- Universidade Federal de São Paulo
- São José dos Campos
- Brazil
| | - Eudes Eterno Fileti
- Instituto de Ciência e Tecnologia
- Universidade Federal de São Paulo
- São José dos Campos
- Brazil
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Long R, English NJ, Prezhdo OV. Minimizing Electron-Hole Recombination on TiO2 Sensitized with PbSe Quantum Dots: Time-Domain Ab Initio Analysis. J Phys Chem Lett 2014; 5:2941-6. [PMID: 26278240 DOI: 10.1021/jz5013627] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
TiO2 sensitized with quantum dots (QDs) gives efficient photovoltaic and photocatalytic systems due to high stability and large absorption cross sections of QDs and rapid photoinduced charge separation at the interface. The yields of the light-induced processes are limited by electron-hole recombination that also occurs at the interface. We combine ab initio nonadiabatic molecular dynamics with analytic theory to investigate the experimentally studied charge recombination at the PbSe QD-TiO2 interface. The time-domain atomistic simulation directly mimics the laser experiment and generates important details of the recombination mechanism. The process occurs due to coupling of the electronic subsystem to polar optical modes of the TiO2 surface. The inelastic electron-phonon scattering happens on a picosecond time scale, while the elastic scattering takes 40 fs. Counter to expectations, the donor-acceptor bonding strengthens at an elevated temperature. An analytic theory extends the simulation results to larger QDs and longer QD-TiO2 bridges. It shows that the electron-hole recombination rate decreases significantly for longer bridges and larger dots and that the main effect arises due to reduced donor-acceptor coupling rather than changes in the donor-acceptor energy gap. The study indicates that by varying QD size or ligands one can reduce charge losses while still maintaining efficient charge separation, providing design principles for optimizing solar cell design and increasing photon-to-electron conversion efficiencies.
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Affiliation(s)
- Run Long
- ‡Department of Chemistry, University of Southern California, 3620 McClintock Avenue, Los Angeles, California 90089, United States
| | | | - Oleg V Prezhdo
- ‡Department of Chemistry, University of Southern California, 3620 McClintock Avenue, Los Angeles, California 90089, United States
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Long R, Prezhdo OV. Asymmetry in the electron and hole transfer at a polymer-carbon nanotube heterojunction. NANO LETTERS 2014; 14:3335-3341. [PMID: 24841921 DOI: 10.1021/nl500792a] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
To achieve a high photon-to-charge conversion efficiency, the electron-hole pair generated by photon absorption in organic photovoltaic systems must overcome the Coulomb attraction, which often results in voltage loss. Bearing this in mind, we performed ab initio time-domain simulations of the charge separation and energy relaxation across an interface formed by poly(3-hexylthiophene) (P3HT) and a single-walled carbon nanotube (CNT). The dynamics of the positive and negative charges showed strong asymmetry. Photoexcitation of the polymer leads to a 100 fs electron transfer, in agreement with the experiment, followed by a loss of 0.6 eV of energy within 0.5 ps. Photoexcitation of the CNT leads to hole transfer, which requires nearly 2 ps, but loses only 0.3 eV of energy. The strong disparity arises due to the differences in the localization of the photoexcited donor states, the number densities of the acceptor states, and the phonon modes involved. Used as a chromophore, P3HT produces faster charge separation but leads to larger energy losses and cannot harvest light in the red region of the solar spectrum. In contrast, CNT absorbs a broader range of photons and reduces energy losses but gives a less efficient charge separation. The complementary properties of the two chromophores can be utilized to improve the performance of solar cells by optimizing simultaneously light harvesting, charge separation, and energy relaxation, which affect the photovoltaic yield, current, and voltage.
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Affiliation(s)
- Run Long
- School of Physics, Complex & Adaptive Systems Laboratory, University College Dublin , Belfield, Dublin 4, Ireland
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Rasmussen AM, Ramakrishna S, Weiss EA, Seideman T. Theory of ultrafast photoinduced electron transfer from a bulk semiconductor to a quantum dot. J Chem Phys 2014; 140:144102. [DOI: 10.1063/1.4870335] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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Tafen DN, Long R, Prezhdo OV. Dimensionality of nanoscale TiO2 determines the mechanism of photoinduced electron injection from a CdSe nanoparticle. NANO LETTERS 2014; 14:1790-1796. [PMID: 24611556 DOI: 10.1021/nl404352a] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Assumptions about electron transfer (ET) mechanisms guide design of catalytic, photovoltaic, and electronic systems. We demonstrate that the mechanism of ET from a CdSe quantum dot (QD) into nanoscale TiO2 depends on TiO2 dimensionality. The injection into a TiO2 QD is adiabatic due to strong donor-acceptor coupling, arising from unsaturated chemical bonds on the QD surface, and low density of acceptor states. In contrast, the injection into a TiO2 nanobelt (NB) is nonadiabatic, because the state density is high, the donor-acceptor coupling is weak, and multiple phonons accommodate changes in the electronic energy. The CdSe adsorbant breaks symmetry of delocalized TiO2 NB states, relaxing coupling selection rules, and generating more ET channels. Both mechanisms can give efficient ultrafast injection. However, the dependence on system properties is very different for the two mechanisms, demonstrating that the fundamental principles leading to efficient charge separation depend strongly on the type of nanoscale material.
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Affiliation(s)
- De Nyago Tafen
- National Energy Technology Laboratory, 1450 Queen Avenue SW, Albany, Oregon 97321, United States
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