1
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Wang CI, Maier JC, Jackson NE. Accessing the electronic structure of liquid crystalline semiconductors with bottom-up electronic coarse-graining. Chem Sci 2024; 15:8390-8403. [PMID: 38846409 PMCID: PMC11151863 DOI: 10.1039/d3sc06749a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 05/01/2024] [Indexed: 06/09/2024] Open
Abstract
Understanding the relationship between multiscale morphology and electronic structure is a grand challenge for semiconducting soft materials. Computational studies aimed at characterizing these relationships require the complex integration of quantum-chemical (QC) calculations, all-atom and coarse-grained (CG) molecular dynamics simulations, and back-mapping approaches. However, these methods pose substantial computational challenges that limit their application to the requisite length scales of soft material morphologies. Here, we demonstrate the bottom-up electronic coarse-graining (ECG) of morphology-dependent electronic structure in the liquid-crystal-forming semiconductor, 2-(4-methoxyphenyl)-7-octyl-benzothienobenzothiophene (BTBT). ECG is applied to construct density functional theory (DFT)-accurate valence band Hamiltonians of the isotropic and smectic liquid crystal (LC) phases using only the CG representation of BTBT. By bypassing the atomistic resolution and its prohibitive computational costs, ECG enables the first calculations of the morphology dependence of the electronic structure of charge carriers across LC phases at the ∼20 nm length scale, with robust statistical sampling. Kinetic Monte Carlo (kMC) simulations reveal a strong morphology dependence on zero-field charge mobility among different LC phases as well as the presence of two-molecule charge carriers that act as traps and hinder charge transport. We leverage these results to further evaluate the feasibility of developing mesoscopic, field-based ECG models in future works. The fully CG approach to electronic property predictions in LC semiconductors opens a new computational direction for designing electronic processes in soft materials at their characteristic length scales.
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Affiliation(s)
- Chun-I Wang
- Department of Chemistry, University of Illinois at Urbana-Champaign 505 S Mathews Avenue Urbana Illinois 61801 USA
| | - J Charlie Maier
- Department of Chemistry, University of Illinois at Urbana-Champaign 505 S Mathews Avenue Urbana Illinois 61801 USA
| | - Nicholas E Jackson
- Department of Chemistry, University of Illinois at Urbana-Champaign 505 S Mathews Avenue Urbana Illinois 61801 USA
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2
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Logrado AL, Cassiano TDSA, da Cunha WF, Gargano R, E Silva GM, de Oliveira Neto PH. Width effects on bilayer graphene nanoribbon polarons. Phys Chem Chem Phys 2024; 26:14948-14959. [PMID: 38739011 DOI: 10.1039/d4cp00760c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
Recent progress in nanoelectronics suggests that stacking armchair graphene nanoribbons (AGNRs) into bilayer systems can generate materials with emergent quasiparticle properties. In this context, the impact of width changes is especially relevant. However, its effect on charged carriers remains elusive. In this work, we investigate the effect of width and interlayer interaction changes on polaron states via a hybrid Hamiltonian that couples the electronic and lattice interactions. Results show the rising of two interlayer polarons: the non-symmetric and the symmetric. The coupling strength needed to induce the transition between states depends on the nanoribbon width, being at the most extreme case of ≈174 meV. Electronic properties such as the coupling strength threshold, carrier size, and gap are shown to respect the AGNR width family 3p, 3p + 1, and 3p + 2 rule. The findings demonstrate that strong interlayer interaction simultaneously delocalizes the carriers and reduces the gap up to 0.6 eV. Additionally, it is found that some layers are more prone to share charge, indicating a potential heterogeneous stacking where a particular electronic pathway is favored. The results present an encouraging prospect for integrating AGNR bilayers in future flexible electronics.
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Affiliation(s)
- André Lima Logrado
- Institute of Physics, University of Brasília, 70919-970, Brasília, Brazil.
| | | | | | - Ricardo Gargano
- Institute of Physics, University of Brasília, 70919-970, Brasília, Brazil.
| | | | - Pedro Henrique de Oliveira Neto
- Institute of Physics, University of Brasília, 70919-970, Brasília, Brazil.
- International Center of Physics, University of Brasília, 70919-970, Brazil
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3
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Cassiano TSA, Pereira ML, E Silva GM, de Oliveira Neto PH, Ribeiro LA. Large polarons in two-dimensional fullerene networks: the crucial role of anisotropy in charge transport. NANOSCALE 2024; 16:2337-2346. [PMID: 38086667 DOI: 10.1039/d3nr04920e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2024]
Abstract
The recent synthesis of a two-dimensional quasi-hexagonal-phase monolayer network of C60 molecules, known as qHPC60, holds significant promise for future semiconductor applications. However, the mechanism behind charge transport in these networks remains unknown. In this study, we developed a Holstein-Peierls Hamiltonian model to investigate charge transport in qHPC60, incorporating both local and non-local electron-phonon couplings. Our computational approach involved identifying suitable semi-empirical parameters to realize the formation of stable polarons in this material. The results unveiled the formation of stable large polarons as the primary carriers in the charge transport throughout qHPC60. To explore polaron transport properties, we conducted dynamic simulations within the picosecond time scale while subjecting the system to an external electric field. Our analysis emphasized the substantial influence of anisotropy on shaping mobile polarons, with an anisotropy coefficient of at least 50%. The polarons exhibited velocities within the acoustic regime ranging from 0.5-1.5 nm ps-1. While these velocities are comparable to those observed in high-end organic molecular crystals, they are considerably lower than those in graphene and conducting polymers. With qHPC60 possessing a semiconducting band gap of approximately 1.6 eV, our findings shed light on its potential application in flat electronics, overcoming the null-gap predicament of graphene.
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Affiliation(s)
- T S A Cassiano
- University of Brasília, Institute of Physics, 70.910-900, Brasília, Brazil.
| | - M L Pereira
- International Center of Physics, Institute of Physics, University of Brasília, Faculty of Technology, Department of Electrical Engineering, 70910-900, Brasília, Brazil
| | - G M E Silva
- University of Brasília, Institute of Physics, 70.910-900, Brasília, Brazil.
| | | | - L A Ribeiro
- University of Brasília, Institute of Physics, 70.910-900, Brasília, Brazil.
- Computational Materials Laboratory, LCCMat, Institute of Physics, University of Brasília, 70910-900, Brasília, Brazil
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4
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Lin HH, Wang CI, Yang CH, Secario MK, Hsu CP. Two-Step Machine Learning Approach for Charge-Transfer Coupling with Structurally Diverse Data. J Phys Chem A 2024; 128:271-280. [PMID: 38157315 DOI: 10.1021/acs.jpca.3c04524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
Electronic coupling is important in determining charge-transfer rates and dynamics. Coupling strength is sensitive to both intermolecular, e.g., orientation or distance, and intramolecular degrees of freedom. Hence, it is challenging to build an accurate machine learning model to predict electronic coupling of molecular pairs, especially for those derived from the amorphous phase, for which intermolecular configurations are much more diverse than those derived from crystals. In this work, we devise a new prediction algorithm that employs two consecutive KRR models. The first model predicts molecular orbitals (MOs) from structural variation for each fragment, and coupling is further predicted by using the overlap integral included in a second model. With our two-step procedure, we achieved mean absolute errors of 0.27 meV for an ethylene dimer and 1.99 meV for a naphthalene pair, much improved accuracy amounting to 14-fold and 3-fold error reductions, respectively. In addition, MOs from the first model can also be the starting point to obtain other quantum chemical properties from atomistic structures. This approach is also compatible with a MO predictor with sufficient accuracy.
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Affiliation(s)
- Hung-Hsuan Lin
- Institute of Chemistry, Academia Sinica, 128 Section 2 Academia Road, Nankang, Taipei 115, Taiwan
- Molecular Science and Digital Innovation Center, Genetics Generation Advancement Corp, No. 28, Ln. 36, Xinhu First Rd., Neihu, Taipei 114, Taiwan
| | - Chun-I Wang
- Institute of Chemistry, Academia Sinica, 128 Section 2 Academia Road, Nankang, Taipei 115, Taiwan
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Chou-Hsun Yang
- Institute of Chemistry, Academia Sinica, 128 Section 2 Academia Road, Nankang, Taipei 115, Taiwan
| | - Muhammad Khari Secario
- Institute of Chemistry, Academia Sinica, 128 Section 2 Academia Road, Nankang, Taipei 115, Taiwan
- Taiwan International Graduate Program on Sustainable Chemical Science & Technology, Academia Sinica Institute of Chemistry, 128 Academia Road Sec.2, Nankang, Taipei 115, Taiwan
- Department of Applied Chemistry, National Yang Ming Chiao Tung University, 1001 University Road, Hsinchu 300, Taiwan
| | - Chao-Ping Hsu
- Institute of Chemistry, Academia Sinica, 128 Section 2 Academia Road, Nankang, Taipei 115, Taiwan
- Division of Physics, National Center for Theoretical Sciences, 1, Section 4, Roosevelt Road, Taipei 106, Taiwan
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5
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Taouali W, Alimi K, Sindhoo Nangraj A, Casida ME. Density-functional theory (DFT) and time-dependent DFT study of the chemical and physical origins of key photoproperties of end-group derivatives of a nonfullerene acceptor molecule for bulk heterojunction organic solar cells. J Comput Chem 2023; 44:2130-2148. [PMID: 37452478 DOI: 10.1002/jcc.27186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 06/18/2023] [Accepted: 06/22/2023] [Indexed: 07/18/2023]
Abstract
As emphasized in a recent review article (Chem. Rev. 2022, 122, 14180), organic solar cell (OSC) photoconversion efficiency has been rapidly evolving with results increasingly comparable to those of traditional inorganic solar cells. Historically, OSC performance improvement focused first on the morphology of P3HT:PC 61 BM solar cells then went through different stages to shift lately interest towards nonfullerene acceptors (NFAs) as a replacement ofPC 61 BM acceptor (ACC) molecule. Here, we use density-functional theory (DFT) and time-dependent DFT to investigate four novel NFAs of A-D-A (acceptor-donor-acceptor) form derived from the recently synthesized IDIC-4Cl (Dyes Pigm. 2019, 166, 196). Our level of theory is carefully evaluated for IDIC-4Cl and then applied to the four novel NFAs in order to understand how chemical modifications lead to physical changes in cyclic voltammetry (CV) frontier molecular orbital energies and absorption spectra in solution. Finally we design and apply a new type of Scharber plot for NFAs based upon some simple but we think reasonable assumptions. Unlike the original Scharber plots where a larger DON band gap favors a larger PCE, our modified Scharber plot reflects the fact that a smaller ACC band gap may favor PCE by filling in gaps in the DON acceptor spectrum. We predict that only the candidate molecule with the least good acceptor A, with the highest frontier molecular orbital energies, and one of the larger CV lowest unoccupied molecular orbital (LUMO) - highest unoccupied molecular orbital (HOMO) gaps, will yield a PM6:ACC PCE exceeding that of the parent IDIC-4Cl ACC. This candidate also shows the largest oscillator strength for the primary1 (HOMO, LUMO) charge- transfer transition and the largest degree of delocalization of charge transfer of any of the ACC molecules investigated here.
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Affiliation(s)
- Walid Taouali
- Laboratoire de Recherche (LR18ES19), Synthèse Asymétrique et Ingénierie Moléculaire de Matériaux Organiques pour l'Électroniques Organiques, Faculté des Sciences de Monastir, Université de Monastir, Monastir, Tunisia
| | - Kamel Alimi
- Laboratoire de Recherche (LR18ES19), Synthèse Asymétrique et Ingénierie Moléculaire de Matériaux Organiques pour l'Électroniques Organiques, Faculté des Sciences de Monastir, Université de Monastir, Monastir, Tunisia
- Institut National de Recherche et d'Analyse Physicochimique (INRAP) pole technologique Sidi Thabet, Ariana, Tunisia
| | - Asma Sindhoo Nangraj
- State Key Laboratory of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai, China
| | - Mark E Casida
- Laboratoire de Spectrométrie, Interactions et Chimie théorique (SITh), Département de Chimie Moléculaire (DCM, UMR CNRS/UGA 5250), Institut de Chimie Moléculaire de Grenoble (ICMG, FR2607), Université Grenoble Alpes (UGA), Grenoble, France
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6
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Müller K, Schellhammer KS, Gräßler N, Debnath B, Liu F, Krupskaya Y, Leo K, Knupfer M, Ortmann F. Directed exciton transport highways in organic semiconductors. Nat Commun 2023; 14:5599. [PMID: 37699907 PMCID: PMC10497625 DOI: 10.1038/s41467-023-41044-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 08/21/2023] [Indexed: 09/14/2023] Open
Abstract
Exciton bandwidths and exciton transport are difficult to control by material design. We showcase the intriguing excitonic properties in an organic semiconductor material with specifically tailored functional groups, in which extremely broad exciton bands in the near-infrared-visible part of the electromagnetic spectrum are observed by electron energy loss spectroscopy and theoretically explained by a close contact between tightly packing molecules and by their strong interactions. This is induced by the donor-acceptor type molecular structure and its resulting crystal packing, which induces a remarkable anisotropy that should lead to a strongly directed transport of excitons. The observations and detailed understanding of the results yield blueprints for the design of molecular structures in which similar molecular features might be used to further explore the tunability of excitonic bands and pave a way for organic materials with strongly enhanced transport and built-in control of the propagation direction.
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Affiliation(s)
- Kai Müller
- Center for Advancing Electronics Dresden, Technische Universität Dresden, 01062, Dresden, Germany
- Institut für Theoretische Physik, Technische Universität Dresden, 01062, Dresden, Germany
| | - Karl S Schellhammer
- Center for Advancing Electronics Dresden, Technische Universität Dresden, 01062, Dresden, Germany
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01062, Dresden, Germany
| | - Nico Gräßler
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01062, Dresden, Germany
- Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstr. 20, 01069, Dresden, Germany
| | - Bipasha Debnath
- Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstr. 20, 01069, Dresden, Germany
| | - Fupin Liu
- Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstr. 20, 01069, Dresden, Germany
| | - Yulia Krupskaya
- Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstr. 20, 01069, Dresden, Germany
| | - Karl Leo
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01062, Dresden, Germany
| | - Martin Knupfer
- Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstr. 20, 01069, Dresden, Germany
| | - Frank Ortmann
- Center for Advancing Electronics Dresden, Technische Universität Dresden, 01062, Dresden, Germany.
- Department of Chemistry, TUM School of Natural Sciences, Technische Universität München, Lichtenbergstr. 4, 85748, Garching b. München, Germany.
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7
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Knepp ZJ, Masso GB, Fredin LA. Efficiently predicting directional carrier mobilities in organic materials with the Boltzmann transport equation. J Chem Phys 2023; 158:064704. [PMID: 36792516 DOI: 10.1063/5.0128125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Describing charge carrier anisotropy in crystalline organic semiconductors with ab initio methods is challenging because of the weak intermolecular interactions that lead to both localized and delocalized charge transport mechanisms. Small polaron hopping models (localized) are generally used to describe materials with small charge carrier mobilities, while periodic band models (delocalized) are used to describe materials with high charge carrier mobilities. Here, we prove the advantage of applying the constant relaxation time approximation of the Boltzmann transport equation (BTE) to efficiently predict the anisotropic hole mobilities of several unsubstituted (anthracene, tetracene, pentacene, and hexacene) and substituted (2,6-diphenylanthracene, rubrene, and TIPS-pentacene) high-mobility n-acene single crystals. Several density functionals are used to optimize the crystals, and the composite density functional PBEsol0-3c/sol-def2-mSVP predicts the most experimentally similar geometries, adequate indirect bandgaps, and the theoretically consistent n-acene charge transport mobility trend. Similarities between BTE and Marcus mobilities are presented for each crystal. BTE and Marcus charge carrier mobilities computed at the same geometry result in similar mobility trends, differing mostly in materials with more substitutions or structurally complex substituents. By using a reduced number of calculations, BTE is able to predict anisotropic carrier mobilities efficiently and effectively for a range of high-mobility organic semiconductors.
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Affiliation(s)
- Zachary J Knepp
- Department of Chemistry, Lehigh University, 6 E. Packer Ave., Bethlehem, Pennsylvania 18015, USA
| | - Gabriel B Masso
- Department of Chemistry, Lehigh University, 6 E. Packer Ave., Bethlehem, Pennsylvania 18015, USA
| | - Lisa A Fredin
- Department of Chemistry, Lehigh University, 6 E. Packer Ave., Bethlehem, Pennsylvania 18015, USA
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8
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Balzer D, Kassal I. Even a little delocalization produces large kinetic enhancements of charge-separation efficiency in organic photovoltaics. SCIENCE ADVANCES 2022; 8:eabl9692. [PMID: 35960797 PMCID: PMC9374333 DOI: 10.1126/sciadv.abl9692] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 06/28/2022] [Indexed: 05/25/2023]
Abstract
In organic photovoltaics, charges can separate efficiently even if their Coulomb attraction is an order of magnitude greater than the available thermal energy. Delocalization has been suggested to explain this fact, because it could increase the initial separation of charges in the charge-transfer (CT) state, reducing their attraction. However, understanding the mechanism requires a kinetic model of delocalized charge separation, which has proven difficult because it involves tracking the correlated quantum-mechanical motion of the electron and the hole in large simulation boxes required for disordered materials. Here, we report the first three-dimensional simulations of charge-separation dynamics in the presence of disorder, delocalization, and polaron formation, finding that even slight delocalization, across less than two molecules, can substantially enhance the charge-separation efficiency, even starting with thermalized CT states. Delocalization does not enhance efficiency by reducing the Coulomb attraction; instead, the enhancement is a kinetic effect produced by the increased overlap of electronic states.
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9
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Peng WT, Brey D, Giannini S, Dell’Angelo D, Burghardt I, Blumberger J. Exciton Dissociation in a Model Organic Interface: Excitonic State-Based Surface Hopping versus Multiconfigurational Time-Dependent Hartree. J Phys Chem Lett 2022; 13:7105-7112. [PMID: 35900333 PMCID: PMC9376959 DOI: 10.1021/acs.jpclett.2c01928] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 07/19/2022] [Indexed: 05/20/2023]
Abstract
Quantum dynamical simulations are essential for a molecular-level understanding of light-induced processes in optoelectronic materials, but they tend to be computationally demanding. We introduce an efficient mixed quantum-classical nonadiabatic molecular dynamics method termed eXcitonic state-based Surface Hopping (X-SH), which propagates the electronic Schrödinger equation in the space of local excitonic and charge-transfer electronic states, coupled to the thermal motion of the nuclear degrees of freedom. The method is applied to exciton decay in a 1D model of a fullerene-oligothiophene junction, and the results are compared to the ones from a fully quantum dynamical treatment at the level of the Multilayer Multiconfigurational Time-Dependent Hartree (ML-MCTDH) approach. Both methods predict that charge-separated states are formed on the 10-100 fs time scale via multiple "hot-exciton dissociation" pathways. The results demonstrate that X-SH is a promising tool advancing the simulation of photoexcited processes from the molecular to the true nanomaterials scale.
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Affiliation(s)
- Wei-Tao Peng
- Department
of Physics and Astronomy and Thomas Young Centre, University College London, London WC1E 6BT, United Kingdom
| | - Dominik Brey
- Institute
of Physical and Theoretical Chemistry, Goethe
University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | - Samuele Giannini
- Department
of Physics and Astronomy and Thomas Young Centre, University College London, London WC1E 6BT, United Kingdom
| | - David Dell’Angelo
- Department
of Physics and Astronomy and Thomas Young Centre, University College London, London WC1E 6BT, United Kingdom
| | - Irene Burghardt
- Institute
of Physical and Theoretical Chemistry, Goethe
University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | - Jochen Blumberger
- Department
of Physics and Astronomy and Thomas Young Centre, University College London, London WC1E 6BT, United Kingdom
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10
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Sneyd A, Beljonne D, Rao A. A New Frontier in Exciton Transport: Transient Delocalization. J Phys Chem Lett 2022; 13:6820-6830. [PMID: 35857739 PMCID: PMC9340810 DOI: 10.1021/acs.jpclett.2c01133] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 07/18/2022] [Indexed: 05/20/2023]
Abstract
Efficient exciton transport is crucial to the application of organic semiconductors (OSCs) in light-harvesting devices. While the physics of exciton transport in highly disordered media is well-explored, the description of transport in structurally and energetically ordered OSCs is less established, despite such materials being favorable for devices. In this Perspective we describe and highlight recent research pointing toward a highly efficient exciton transport mechanism which occurs in ordered OSCs, transient delocalization. Here, exciton-phonon couplings play a critical role in allowing localized exciton states to temporarily access higher-energy delocalized states whereupon they move large distances. The mechanism shows great promise for facilitating long-range exciton transport and may allow for improved device efficiencies and new device architectures. However, many fundamental questions on transient delocalization remain to be answered. These questions and suggested next steps are summarized.
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Affiliation(s)
- Alexander
J. Sneyd
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - David Beljonne
- Laboratory
for Chemistry of Novel Materials, University
of Mons, Mons 7000, Belgium
| | - Akshay Rao
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, Cambridge CB3 0HE, United Kingdom
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11
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Giannini S, Peng WT, Cupellini L, Padula D, Carof A, Blumberger J. Exciton transport in molecular organic semiconductors boosted by transient quantum delocalization. Nat Commun 2022; 13:2755. [PMID: 35589694 PMCID: PMC9120088 DOI: 10.1038/s41467-022-30308-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 04/26/2022] [Indexed: 11/09/2022] Open
Abstract
Designing molecular materials with very large exciton diffusion lengths would remove some of the intrinsic limitations of present-day organic optoelectronic devices. Yet, the nature of excitons in these materials is still not sufficiently well understood. Here we present Frenkel exciton surface hopping, an efficient method to propagate excitons through truly nano-scale materials by solving the time-dependent Schrödinger equation coupled to nuclear motion. We find a clear correlation between diffusion constant and quantum delocalization of the exciton. In materials featuring some of the highest diffusion lengths to date, e.g. the non-fullerene acceptor Y6, the exciton propagates via a transient delocalization mechanism, reminiscent to what was recently proposed for charge transport. Yet, the extent of delocalization is rather modest, even in Y6, and found to be limited by the relatively large exciton reorganization energy. On this basis we chart out a path for rationally improving exciton transport in organic optoelectronic materials.
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Affiliation(s)
- Samuele Giannini
- Department of Physics and Astronomy and Thomas Young Centre, University College London, WC1E 6BT, London, UK.
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, 7000, Mons, Belgium.
| | - Wei-Tao Peng
- Department of Physics and Astronomy and Thomas Young Centre, University College London, WC1E 6BT, London, UK
| | - Lorenzo Cupellini
- Dipartimento di Chimica e Chimica Industriale, Universitá di Pisa, Via G. Moruzzi 13, 56124, Pisa, Italy
| | - Daniele Padula
- Dipartimento di Biotecnologie, Chimica e Farmacia, Universitá di Siena, Via A. Moro 2, 53100, Siena, Italy
| | - Antoine Carof
- Laboratoire de Physique et Chimie Théoriques, CNRS, UMR No. 7019, Université de Lorraine, BP 239, 54506, Vandoeuvre-lés-Nancy Cedex, France
| | - Jochen Blumberger
- Department of Physics and Astronomy and Thomas Young Centre, University College London, WC1E 6BT, London, UK.
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12
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Giannini S, Blumberger J. Charge Transport in Organic Semiconductors: The Perspective from Nonadiabatic Molecular Dynamics. Acc Chem Res 2022; 55:819-830. [PMID: 35196456 PMCID: PMC8928466 DOI: 10.1021/acs.accounts.1c00675] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
![]()
Organic semiconductors (OSs) are an exciting
class of materials
that have enabled disruptive technologies in this century including
large-area electronics, flexible displays, and inexpensive solar cells.
All of these technologies rely on the motion of electrical charges
within the material and the diffusivity of these charges critically
determines their performance. In this respect, it is remarkable that
the nature of the charge transport in these materials has puzzled
the community for so many years, even for apparently simple systems
such as molecular single crystals: some experiments would better fit
an interpretation in terms of a localized particle picture, akin to
molecular or biological electron transfer, while others are in better
agreement with a wave-like interpretation, more akin to band transport
in metals. Exciting recent progress in the theory and simulation
of charge
carrier transport in OSs has now led to a unified understanding of
these disparate findings, and this Account will review one of these
tools developed in our laboratory in some detail: direct charge carrier
propagation by quantum-classical nonadiabatic molecular dynamics.
One finds that even in defect-free crystals the charge carrier can
either localize on a single molecule or substantially delocalize over
a large number of molecules depending on the relative strength of
electronic couplings between the molecules, reorganization, or charge
trapping energy of the molecule and thermal fluctuations of electronic
couplings and site energies, also known as electron–phonon
couplings. Our simulations predict that in molecular OSs exhibiting
some of
the highest measured charge mobilities to date, the charge carrier
forms “flickering” polarons, objects that are delocalized
over 10–20 molecules on average and that constantly change
their shape and extension under the influence of thermal disorder.
The flickering polarons propagate through the OS by short (≈10
fs long) bursts of the wave function that lead to an expansion of
the polaron to about twice its size, resulting in spatial displacement,
carrier diffusion, charge mobility, and electrical conductivity. Arguably
best termed “transient delocalization”, this mechanistic
scenario is very similar to the one assumed in transient localization
theory and supports its assertions. We also review recent applications
of our methodology to charge transport in disordered and nanocrystalline
samples, which allows us to understand the influence of defects and
grain boundaries on the charge propagation. Unfortunately, the
energetically favorable packing structures of
typical OSs, whether molecular or polymeric, places fundamental constraints
on charge mobilities/electronic conductivity compared to inorganic
semiconductors, which limits their range of applications. In this
Account, we review the design rules that could pave the way for new
very high-mobility OS materials and we argue that 2D covalent organic
frameworks are one of the most promising candidates to satisfy them. We conclude that our nonadiabatic dynamics method is a powerful
approach for predicting charge carrier transport in crystalline and
disordered materials. We close with a brief outlook on extensions
of the method to exciton transport, dissociation, and recombination.
This will bring us a step closer to an understanding of the birth,
survival, and annihiliation of charges at interfaces of optoelectronic
devices.
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Affiliation(s)
- Samuele Giannini
- Department of Physics and Astronomy and Thomas Young Centre, University College London, London WC1E 6BT, United Kingdom
| | - Jochen Blumberger
- Department of Physics and Astronomy and Thomas Young Centre, University College London, London WC1E 6BT, United Kingdom
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13
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Ziogos OG, Blumberger J. Ultrafast estimation of electronic couplings for electron transfer between pi-conjugated organic molecules. II. J Chem Phys 2021; 155:244110. [PMID: 34972358 DOI: 10.1063/5.0076555] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The development of highly efficient methods for the calculation of electronic coupling matrix elements between the electron donor and acceptor is an important goal in theoretical organic semiconductor research. In Paper I [F. Gajdos, S. Valner, F. Hoffmann, J. Spencer, M. Breuer, A. Kubas, M. Dupuis, and J. Blumberger, J. Chem. Theory Comput. 10, 4653 (2014)], we introduced the analytic overlap method (AOM) for this purpose, which is an ultrafast electronic coupling estimator parameterized to and orders of magnitude faster than density functional theory (DFT) calculations at a reasonably small loss in accuracy. In this work, we reparameterize and extend the AOM to molecules containing nitrogen, oxygen, fluorine, and sulfur heteroatoms using 921 dimer configurations from the recently introduced HAB79 dataset. We find again a very good linear correlation between the frontier orbital overlap, calculated ultrafast in an optimized minimum Slater basis, and DFT reference electronic couplings. The new parameterization scheme is shown to be transferable to sulfur-containing polyaromatic hydrocarbons in experimentally resolved dimeric configurations. Our extension of the AOM enables high-throughput screening of very large databases of chemically diverse organic crystal structures and the application of computationally intense non-adiabatic molecular dynamics methods to charge transport in state-of-the-art organic semiconductors, e.g., non-fullerene acceptors.
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Affiliation(s)
- Orestis George Ziogos
- Department of Physics and Astronomy and Thomas Young Centre, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Jochen Blumberger
- Department of Physics and Astronomy and Thomas Young Centre, University College London, Gower Street, London WC1E 6BT, United Kingdom
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14
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Ellis M, Yang H, Giannini S, Ziogos OG, Blumberger J. Impact of Nanoscale Morphology on Charge Carrier Delocalization and Mobility in an Organic Semiconductor. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2104852. [PMID: 34558126 DOI: 10.1002/adma.202104852] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 08/11/2021] [Indexed: 06/13/2023]
Abstract
A central challenge of organic semiconductor research is to make cheap, disordered materials that exhibit high electrical conductivity. Unfortunately, this endeavor is hampered by the poor fundamental understanding of the relationship between molecular packing structure and charge carrier mobility. Here a novel computational methodology is presented that fills this gap. Using a melt-quench procedure it is shown that amorphous pentacene spontaneously self-assembles to nanocrystalline structures that, at long quench times, form the characteristic herringbone layer of the single crystal. Quantum dynamical simulations of electron hole transport show a clear correlation between the crystallinity of the sample, the quantum delocalization, and the mobility of the charge carrier. Surprisingly, the long-held belief that charge carriers form relatively localized polarons in disordered OS is only valid for fully amorphous structures-for nanocrystalline and crystalline samples, significant charge carrier delocalization over several nanometers occurs that underpins their improved conductivities. The good agreement with experimentally available data makes the presented methodology a robust computational tool for the predictive engineering of disordered organic materials.
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Affiliation(s)
- Matthew Ellis
- Department of Physics and Astronomy and Thomas Young Centre London, University College London, Gower Street, London, WC1E 6BT, UK
| | - Hui Yang
- Department of Physics and Astronomy and Thomas Young Centre London, University College London, Gower Street, London, WC1E 6BT, UK
| | - Samuele Giannini
- Department of Physics and Astronomy and Thomas Young Centre London, University College London, Gower Street, London, WC1E 6BT, UK
| | - Orestis G Ziogos
- Department of Physics and Astronomy and Thomas Young Centre London, University College London, Gower Street, London, WC1E 6BT, UK
| | - Jochen Blumberger
- Department of Physics and Astronomy and Thomas Young Centre London, University College London, Gower Street, London, WC1E 6BT, UK
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15
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Elsner J, Giannini S, Blumberger J. Mechanoelectric Response of Single-Crystal Rubrene from Ab Initio Molecular Dynamics. J Phys Chem Lett 2021; 12:5857-5863. [PMID: 34139118 PMCID: PMC8256417 DOI: 10.1021/acs.jpclett.1c01385] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/11/2021] [Indexed: 06/12/2023]
Abstract
A robust understanding of the mechanoelectric response of organic semiconductors is crucial for the development of materials for flexible electronics. In particular, the prospect of using external mechanical strain to induce a controlled modulation in the charge mobility of the material is appealing. Here we develop an accurate computational protocol for the prediction of the mechanical strain dependence of charge mobility. Ab initio molecular dynamics simulations with a van der Waals density functional are carried out to quantify the off-diagonal electronic disorder in the system as a function of strain by the explicit calculation of the thermal distributions of electronic coupling matrix elements. The approach is applied to a representative molecular organic semiconductor, single-crystal rubrene. We find that charge mobility along the high-mobility direction a⃗ increases with compressive strain, as one might expect. However, the increase is larger when compressive strain is applied in the perpendicular direction than in the parallel direction with respect to a⃗, in agreement with experimental reports. We show that this seemingly counterintuitive result is a consequence of a significantly greater suppression of electronic coupling fluctuations in the range of 50-150 cm-1, when strain is applied in the perpendicular direction. Thus our study highlights the importance of considering off-diagonal electron-phonon coupling in understanding the mechanoelectric response of organic semiconducting crystals. The computational approach developed here is well suited for the accurate prediction of strain-charge mobility relations and should provide a useful tool for the emerging field of molecular strain engineering.
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16
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Pandya R, Alvertis AM, Gu Q, Sung J, Legrand L, Kréher D, Barisien T, Chin AW, Schnedermann C, Rao A. Exciton Diffusion in Highly-Ordered One Dimensional Conjugated Polymers: Effects of Back-Bone Torsion, Electronic Symmetry, Phonons and Annihilation. J Phys Chem Lett 2021; 12:3669-3678. [PMID: 33829788 PMCID: PMC8154834 DOI: 10.1021/acs.jpclett.1c00193] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 03/23/2021] [Indexed: 06/12/2023]
Abstract
Many optoelectronic devices based on organic materials require rapid and long-range singlet exciton transport. Key factors controlling exciton transport include material structure, exciton-phonon coupling and electronic state symmetry. Here, we employ femtosecond transient absorption microscopy to study the influence of these parameters on exciton transport in one-dimensional conjugated polymers. We find that excitons with 21Ag- symmetry and a planar backbone exhibit a significantly higher diffusion coefficient (34 ± 10 cm2 s-1) compared to excitons with 11Bu+ symmetry (7 ± 6 cm2 s-1) with a twisted backbone. We also find that exciton transport in the 21Ag- state occurs without exciton-exciton annihilation. Both 21Ag- and 11Bu+ states are found to exhibit subdiffusive behavior. Ab initio GW-BSE calculations reveal that this is due to the comparable strengths of the exciton-phonon interaction and exciton coupling. Our results demonstrate the link between electronic state symmetry, backbone torsion and phonons in exciton transport in π-conjugated polymers.
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Affiliation(s)
- Raj Pandya
- Cavendish
Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Antonios M. Alvertis
- Cavendish
Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Qifei Gu
- Cavendish
Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Jooyoung Sung
- Cavendish
Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Laurent Legrand
- Sorbonne
Université, CNRS, Institut
des NanoSciences de Paris, INSP, 4 place Jussieu, F-75005 Paris, France
| | - David Kréher
- Sorbonne
Université, CNRS, Institut
Parisien de Chimie Moléculaire (IPCM) UMR 8232, Chimie des
Polymères, 4 Place
Jussieu, 75005 Paris, France
| | - Thierry Barisien
- Sorbonne
Université, CNRS, Institut
des NanoSciences de Paris, INSP, 4 place Jussieu, F-75005 Paris, France
| | - Alex W. Chin
- Sorbonne
Université, CNRS, Institut
des NanoSciences de Paris, INSP, 4 place Jussieu, F-75005 Paris, France
| | - Christoph Schnedermann
- Cavendish
Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Akshay Rao
- Cavendish
Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
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17
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Darghouth AAMHM, Casida ME, Zhu X, Natarajan B, Su H, Humeniuk A, Titov E, Miao X, Mitrić R. Effect of varying the TD-lc-DFTB range-separation parameter on charge and energy transfer in a model pentacene/buckminsterfullerene heterojunction. J Chem Phys 2021; 154:054102. [PMID: 33557554 DOI: 10.1063/5.0024559] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Atomistic modeling of energy and charge transfer at the heterojunction of organic solar cells is an active field with many remaining outstanding questions owing, in part, to the difficulties in performing reliable photodynamics calculations on very large systems. One approach to being able to overcome these difficulties is to design and apply an appropriate simplified method. Density-functional tight binding (DFTB) has become a popular form of approximate density-functional theory based on a minimal valence basis set and neglect of all but two center integrals. We report the results of our tests of a recent long-range correction (lc) [A. Humeniuk and R. Mitrić, J. Chem. Phys. 143, 134120 (2015)] for time-dependent (TD) lc-DFTB by carrying out TD-lc-DFTB fewest switches surface hopping calculations of energy and charge transfer times using the relatively new DFTBABY [A. Humeniuk and R. Mitrić, Comput. Phys. Commun. 221, 174 (2017)] program. An advantage of this method is the ability to run enough trajectories to get meaningful ensemble averages. Our interest in the present work is less in determining exact energy and charge transfer rates than in understanding how the results of these calculations vary with the value of the range-separation parameter (Rlc = 1/μ) for a model organic solar cell heterojunction consisting of a gas-phase van der Waals complex P/F made up of a single pentacene (P) molecule together with a single buckminsterfullerene (F) molecule. The default value of Rlc = 3.03 a0 is found to be much too small as neither energy nor charge transfer is observed until Rlc ≈ 10 a0. Tests at a single geometry show that the best agreement with high-quality ab initio spectra is obtained in the limit of no lc (i.e., very large Rlc). A plot of energy and charge transfer rates as a function of Rlc is provided, which suggests that a value of Rlc ≈ 15 a0 yields the typical literature (condensed-phase) charge transfer time of about 100 fs. However, energy and charge transfer times become as high as ∼300 fs for Rlc ≈ 25 a0. A closer examination of the charge transfer process P*/F → P+/F- shows that the initial electron transfer is accompanied by a partial delocalization of the P hole onto F, which then relocalizes back onto P, consistent with a polaron-like picture in which the nuclei relax to stabilize the resultant redistribution of charges.
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Affiliation(s)
| | - Mark E Casida
- Laboratoire de Spectrométrie, Interactions et Chimie Théorique (SITh), Département de Chimie Moléculaire (DCM), Institut de Chimie Moléculaire de Grenoble (ICMG), Université Grenoble-Alpes, 301 rue de la Chimie, CS 40700, 38058 Grenoble Cedex 9, France
| | - Xi Zhu
- Institute of Advanced Studies, Nanyang Technological University, 60 Nanyang View, 639673, Singapore
| | - Bhaarathi Natarajan
- Institute of Advanced Studies, Nanyang Technological University, 60 Nanyang View, 639673, Singapore
| | - Haibin Su
- Institute of Advanced Studies, Nanyang Technological University, 60 Nanyang View, 639673, Singapore
| | - Alexander Humeniuk
- Institut für Physikalische und Theoretische Chemie, Julius-Maximilians-Universität Würzburg, Emil-Fischer-Straße 42, D-97074 Würzburg, Germany
| | - Evgenii Titov
- Institut für Physikalische und Theoretische Chemie, Julius-Maximilians-Universität Würzburg, Emil-Fischer-Straße 42, D-97074 Würzburg, Germany
| | - Xincheng Miao
- Institut für Physikalische und Theoretische Chemie, Julius-Maximilians-Universität Würzburg, Emil-Fischer-Straße 42, D-97074 Würzburg, Germany
| | - Roland Mitrić
- Institut für Physikalische und Theoretische Chemie, Julius-Maximilians-Universität Würzburg, Emil-Fischer-Straße 42, D-97074 Würzburg, Germany
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18
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Balzer D, Smolders TJAM, Blyth D, Hood SN, Kassal I. Delocalised kinetic Monte Carlo for simulating delocalisation-enhanced charge and exciton transport in disordered materials. Chem Sci 2020; 12:2276-2285. [PMID: 34163994 PMCID: PMC8179315 DOI: 10.1039/d0sc04116e] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Charge transport is well understood in both highly ordered materials (band conduction) or highly disordered ones (hopping conduction). In moderately disordered materials—including many organic semiconductors—the approximations valid in either extreme break down, making it difficult to accurately model the conduction. In particular, describing wavefunction delocalisation requires a quantum treatment, which is difficult in disordered materials that lack periodicity. Here, we present the first three-dimensional model of partially delocalised charge and exciton transport in materials in the intermediate disorder regime. Our approach is based on polaron-transformed Redfield theory, but overcomes several computational roadblocks by mapping the quantum-mechanical techniques onto kinetic Monte Carlo. Our theory, delocalised kinetic Monte Carlo (dKMC), shows that the fundamental physics of transport in moderately disordered materials is that of charges hopping between partially delocalised electronic states. Our results reveal why standard kinetic Monte Carlo can dramatically underestimate mobilities even in disordered organic semiconductors, where even a little delocalisation can substantially enhance mobilities, as well as showing that three-dimensional calculations capture important delocalisation effects neglected in lower-dimensional approximations. The first three-dimensional model of transport in moderately disordered materials shows that a little delocalisation can dramatically enhance mobilities.![]()
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Affiliation(s)
- Daniel Balzer
- School of Chemistry and University of Sydney Nano Institute, University of Sydney NSW 2006 Australia
| | - Thijs J A M Smolders
- School of Chemistry and University of Sydney Nano Institute, University of Sydney NSW 2006 Australia .,Institute for Molecules and Materials, Radboud University 6525 AJ Nijmegen The Netherlands
| | - David Blyth
- School of Mathematics and Physics, University of Queensland St. Lucia QLD 4072 Australia
| | - Samantha N Hood
- School of Mathematics and Physics, University of Queensland St. Lucia QLD 4072 Australia
| | - Ivan Kassal
- School of Chemistry and University of Sydney Nano Institute, University of Sydney NSW 2006 Australia
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