1
|
Gierster L, Turkina O, Deinert JC, Vempati S, Baeta E, Garmshausen Y, Hecht S, Draxl C, Stähler J. Right On Time: Ultrafast Charge Separation Before Hybrid Exciton Formation. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024:e2403765. [PMID: 38874072 DOI: 10.1002/advs.202403765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Indexed: 06/15/2024]
Abstract
Organic/inorganic hybrid systems offer great potential for novel solar cell design combining the tunability of organic chromophore absorption properties with high charge carrier mobilities of inorganic semiconductors. However, often such material combinations do not show the expected performance: while ZnO, for example, basically exhibits all necessary properties for a successful application in light-harvesting, it was clearly outpaced by TiO2 in terms of charge separation efficiency. The origin of this deficiency has long been debated. This study employs femtosecond time-resolved photoelectron spectroscopy and many-body ab initio calculations to identify and quantify all elementary steps leading to the suppression of charge separation at an exemplary organic/ZnO interface. It is demonstrated that charge separation indeed occurs efficiently on ultrafast (350 fs) timescales, but that electrons are recaptured at the interface on a 100 ps timescale and subsequently trapped in a strongly bound (0.7 eV) hybrid exciton state with a lifetime exceeding 5 µs. Thus, initially successful charge separation is followed by delayed electron capture at the interface, leading to apparently low charge separation efficiencies. This finding provides a sufficiently large time frame for counter-measures in device design to successfully implement specifically ZnO and, moreover, invites material scientists to revisit charge separation in various kinds of previously discarded hybrid systems.
Collapse
Affiliation(s)
- Lukas Gierster
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany
- Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Olga Turkina
- Department of Physics, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489, Berlin, Germany
| | - Jan-Christoph Deinert
- Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Sesha Vempati
- Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Elsie Baeta
- Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Yves Garmshausen
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany
| | - Stefan Hecht
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany
- Center for the Science of Materials Berlin, Humboldt-Universität zu Berlin, Zum Großen Windkanal 2, 12489, Berlin, Germany
| | - Claudia Draxl
- Department of Physics, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489, Berlin, Germany
- Center for the Science of Materials Berlin, Humboldt-Universität zu Berlin, Zum Großen Windkanal 2, 12489, Berlin, Germany
| | - Julia Stähler
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany
- Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| |
Collapse
|
2
|
Rijal K, Fuller N, Rudayni F, Zhang N, Zuo X, Berrie CL, Yip HL, Chan WL. Endothermic Charge Separation Occurs Spontaneously in Non-Fullerene Acceptor/Polymer Bulk Heterojunction. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2400578. [PMID: 38762779 DOI: 10.1002/adma.202400578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 04/22/2024] [Indexed: 05/20/2024]
Abstract
Organic photovoltaics (OPVs) based on non-fullerene acceptors (NFAs) have achieved a power conversion efficiency close to 20%. These NFA OPVs can generate free carriers efficiently despite a very small energy level offset at the donor/acceptor interface. Why these NFAs can enable efficient charge separation (CS) with low energy losses remains an open question. Here, the CS process in the PM6:Y6 bulk heterojunction is probed by time-resolved two-photon photoemission spectroscopy. It is found that the CS, the conversion from bound charge transfer (CT) excitons to free carriers, is an endothermic process with an enthalpy barrier of 0.15 eV. The CS can occur spontaneously despite being an endothermic process, which implies that it is driven by entropy. It is further argued that the morphology of the PM6:Y6 film and the anisotropic electron delocalization restrict the electron and hole wavefunctions within the CT exciton such that they can primarily contact each other through point-like junctions. This configuration can maximize the entropic driving force.
Collapse
Affiliation(s)
- Kushal Rijal
- Department of Physics and Astronomy, University of Kansas, Lawrence, KS, 66045, USA
| | - Neno Fuller
- Department of Physics and Astronomy, University of Kansas, Lawrence, KS, 66045, USA
| | - Fatimah Rudayni
- Department of Physics and Astronomy, University of Kansas, Lawrence, KS, 66045, USA
- Department of Physics, Jazan University, Jazan, 45142, Saudi Arabia
| | - Nan Zhang
- Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, 999077, Hong Kong
| | - Xiaobing Zuo
- X-ray Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Cindy L Berrie
- Department of Chemistry, University of Kansas, Lawrence, KS, 66045, USA
| | - Hin-Lap Yip
- Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, 999077, Hong Kong
- School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon, 999077, Hong Kong
- Hong Kong Institute for Clean Energy, City University of Hong Kong, Tat Chee Avenue, Kowloon, 999077, Hong Kong
- Center of Super-Diamond and Advanced Films, City University of Hong Kong, Tat Chee Avenue, Kowloon, 999077, Hong Kong
| | - Wai-Lun Chan
- Department of Physics and Astronomy, University of Kansas, Lawrence, KS, 66045, USA
| |
Collapse
|
3
|
Rudayni F, Rijal K, Fuller N, Chan WL. Enthalpy-uphill exciton dissociation in organic/2D heterostructures promotes free carrier generation. MATERIALS HORIZONS 2024; 11:813-821. [PMID: 38018228 DOI: 10.1039/d3mh01522j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2023]
Abstract
Despite the large binding energy of charge transfer (CT) excitons in type-II organic/2D heterostructures, it has been demonstrated that free carriers can be generated from CT excitons with a long lifetime. Using a model fluorinated zine phthalocyanine (F8ZnPc)/monolayer-WS2 interface, we find that CT excitons can dissociate spontaneously into free carriers despite it being an enthalpy-uphill process. Specifically, it is observed that CT excitons can gain an energy of 250 meV in 50 ps and dissociate into free carriers without any applied electric field. This observation is surprising because excited electrons typically lose energy to the environment and relax to lower energy states. We hypothesize that this abnormal enthalpy-uphill CT exciton dissociation process is driven by entropy gain. Kinetically, the entropic driving force can also reduce the rate for the reverse process - the conversion of free electron-hole pairs back to CT excitons. Hence, this mechanism can potentially explain the very long carrier lifetime observed in organic/2D heterostructures.
Collapse
Affiliation(s)
- Fatimah Rudayni
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, US.
- Department of Physics, Jazan University, Jazan 45142, Saudi Arabia
| | - Kushal Rijal
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, US.
| | - Neno Fuller
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, US.
| | - Wai-Lun Chan
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, US.
| |
Collapse
|
4
|
Liu XY, Chen WK, Fang WH, Cui G. Nonadiabatic Dynamics Simulations for Photoinduced Processes in Molecules and Semiconductors: Methodologies and Applications. J Chem Theory Comput 2023. [PMID: 37984502 DOI: 10.1021/acs.jctc.3c00960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Nonadiabatic dynamics (NAMD) simulations have become powerful tools for elucidating complicated photoinduced processes in various systems from molecules to semiconductor materials. In this review, we present an overview of our recent research on photophysics of molecular systems and periodic semiconductor materials with the aid of ab initio NAMD simulation methods implemented in the generalized trajectory surface-hopping (GTSH) package. Both theoretical backgrounds and applications of the developed NAMD methods are presented in detail. For molecular systems, the linear-response time-dependent density functional theory (LR-TDDFT) method is primarily used to model electronic structures in NAMD simulations owing to its balanced efficiency and accuracy. Moreover, the efficient algorithms for calculating nonadiabatic coupling terms (NACTs) and spin-orbit couplings (SOCs) have been coded into the package to increase the simulation efficiency. In combination with various analysis techniques, we can explore the mechanistic details of the photoinduced dynamics of a range of molecular systems, including charge separation and energy transfer processes in organic donor-acceptor structures, ultrafast intersystem crossing (ISC) processes in transition metal complexes (TMCs), and exciton dynamics in molecular aggregates. For semiconductor materials, we developed the NAMD methods for simulating the photoinduced carrier dynamics within the framework of the Kohn-Sham density functional theory (KS-DFT), in which SOC effects are explicitly accounted for using the two-component, noncollinear DFT method. Using this method, we have investigated the photoinduced carrier dynamics at the interface of a variety of van der Waals (vdW) heterojunctions, such as two-dimensional transition metal dichalcogenides (TMDs), carbon nanotubes (CNTs), and perovskites-related systems. Recently, we extended the LR-TDDFT-based NAMD method for semiconductor materials, allowing us to study the excitonic effects in the photoinduced energy transfer process. These results demonstrate that the NAMD simulations are powerful tools for exploring the photodynamics of molecular systems and semiconductor materials. In future studies, the NAMD simulation methods can be employed to elucidate experimental phenomena and reveal microscopic details as well as rationally design novel photofunctional materials with desired properties.
Collapse
Affiliation(s)
- Xiang-Yang Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610068, P. R. China
| | - Wen-Kai Chen
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Wei-Hai Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
- Hefei National Laboratory, Hefei 230088, P. R. China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
- Hefei National Laboratory, Hefei 230088, P. R. China
| |
Collapse
|
5
|
Liu S, Liu SS, Tang XM, Liu XY, Yang JJ, Cui G, Li L. Solvent effects on the photoinduced charge separation dynamics of directly linked zinc phthalocyanine-perylenediimide dyads: a nonadiabatic dynamics simulation with an optimally tuned screened range-separated hybrid functional. Phys Chem Chem Phys 2023; 25:28452-28464. [PMID: 37846460 DOI: 10.1039/d3cp03517d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2023]
Abstract
Herein, we have employed a combination of the optimally tuned screened range-separated hybrid (OT-SRSH) functional, the polarizable continuum model (PCM), and nonadiabatic dynamics (NAMD) simulations to investigate the photoinduced dynamics of directly linked donor-acceptor dyads formed using zinc phthalocyanine (ZnPc) and perylenediimide (PDI), in which ZnPc is the donor while PDI is the acceptor. Our simulations aim to analyze the behavior of these dyads upon local excitation of the ZnPc moiety in the gas phase and in benzonitrile. Our findings indicate that the presence of a solvent can significantly influence the excited state dynamics of ZnPc-PDI dyads. Specifically, the polar solvent benzonitrile effectively lowers the vertical excitation energies of the charge transfer (CT) state from ZnPc to PDI. As a result, the energetic order of the locally excited (LE) states of ZnPc and the CT states is reversed compared to the gas phase. Consequently, the photoinduced electron transfer (PET) dynamics from ZnPc to PDI, which is absent in the gas phase, takes place in benzonitrile with a time constant of 10.4 ps. Importantly, our present work not only qualitatively agrees with experimental results but also provides in-depth insights into the underlying mechanisms responsible for the photoinduced dynamics of ZnPc-PDI. Moreover, this study emphasizes the importance of appropriately considering solvent effects in NAMD simulation of organic donor-acceptor systems, taking into account the distinct excited state dynamics observed in the gas phase and benzonitrile. Furthermore, the combination of the OT-SRSH functional, the PCM solvent model, and nonadiabatic dynamics simulations shows promise as a strategy for investigating the complex excited state dynamics of organic donor-acceptor systems in solvents. These findings will be valuable for the future design of novel organic donor-acceptor structures with improved performance.
Collapse
Affiliation(s)
- Shuai Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610068, China.
| | - Sha-Sha Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610068, China.
| | - Xiao-Mei Tang
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610068, China.
| | - Xiang-Yang Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610068, China.
| | - Jia-Jia Yang
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610068, China.
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
- Hefei National Laboratory, Hefei 230088, China
| | - Laicai Li
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610068, China.
| |
Collapse
|
6
|
Rijal K, Amos S, Valencia-Acuna P, Rudayni F, Fuller N, Zhao H, Peelaers H, Chan WL. Nanoscale Periodic Trapping Sites for Interlayer Excitons Built by Deformable Molecular Crystal on 2D Crystal. ACS NANO 2023; 17:7775-7786. [PMID: 37042658 DOI: 10.1021/acsnano.3c00541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The nanoscale moiré pattern formed at 2D transition-metal dichalcogenide crystal (TMDC) heterostructures provides periodic trapping sites for excitons, which is essential for realizing various exotic phases such as artificial exciton lattices, Bose-Einstein condensates, and exciton insulators. At organic molecule/TMDC heterostructures, similar periodic potentials can be formed via other degrees of freedom. Here, we utilize the structure deformability of a 2D molecular crystal as a degree of freedom to create a periodic nanoscale potential that can trap interlayer excitons (IXs). Specifically, two semiconducting molecules, PTCDI and PTCDA, which possess similar band gaps and ionization potentials but form different lattice structures on MoS2, are investigated. The PTCDI lattice on MoS2 is distorted geometrically, which lifts the degeneracy of the two molecules within the crystal's unit cell. The degeneracy lifting results in a spatial variation of the molecular orbital energy, with an amplitude and periodicity of ∼0.2 eV and ∼2 nm, respectively. On the other hand, no such energy variation is observed in PTCDA/MoS2, where the PTCDA lattice is much less distorted. The periodic variation in molecular orbital energies provides effective trapping sites for IXs. For IXs formed at PTCDI/MoS2, rapid spatial localization of the electron in the organic layer toward the interface is observed, which demonstrates the effectiveness of these interfacial IX traps.
Collapse
Affiliation(s)
- Kushal Rijal
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Stephanie Amos
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Pavel Valencia-Acuna
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Fatimah Rudayni
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
- Department of Physics, Jazan University, Jazan 45142, Saudi Arabia
| | - Neno Fuller
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Hui Zhao
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Hartwin Peelaers
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Wai-Lun Chan
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| |
Collapse
|
7
|
Chen WK, Cui G, Liu XY. Solvent effects on excited-state relaxation dynamics of paddle-wheel BODIPY-Hexaoxatriphenylene conjugates: Insights from non-adiabatic dynamics simulations. CHINESE J CHEM PHYS 2022. [DOI: 10.1063/1674-0068/cjcp2110214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Understanding the excited state dynamics of donor-acceptor (D-A) complexes is of fundamental importance both experimentally and theoretically. Herein, we have first explored the photoinduced dynamics of a recently synthesized paddle-wheel BODIPY-hexaoxatriphenylene (BODIPY is the abbreviation for BF2-chelated dipyrromethenes) conjugates D-A complexes with the combination of both electronic structure calculations and non-adiabatic dynamics simulations. On the basis of computational results, we concluded that the BODIPY-hexaoxatriphenylene (BH) conjugates will be promoted to the local excited (LE) states of the BODIPY fragments upon excitation, which is followed by the ultrafast exciton transfer from LE state to charge transfer (CT). Instead of the photoinduced electron transfer process proposed in previous experimental work, such a exciton transfer process is accompanied with the photoinduced hole transfer from BODIPY to hexaoxatriphenylene. Additionally, solvent effects are found to play an important role in the photoinduced dynamics. Specifically, the hole transfer dynamics is accelerated by the acetonitrile solvent, which can be ascribed to significant influences of the solvents on the charge transfer states, i.e. the energy gaps between LE and CT excitons are reduced greatly and the non-adiabatic couplings are increased in the meantime. Our present work not only provides valuable insights into the underlying photoinduced mechanism of BH, but also can be helpful for the future design of novel donor-acceptor conjugates with better optoelectronic performance.
Collapse
Affiliation(s)
- Wen-Kai Chen
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Xiang-Yang Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610068, China
| |
Collapse
|
8
|
Mao D, Chen XR, Li DH, Liu XY, Cui G, Li L. Ultrafast charge transfer in a nonfullerene all-small-molecule organic solar cell: a nonadiabatic dynamics simulation with optimally tuned range-separated functional. Phys Chem Chem Phys 2022; 24:27173-27183. [DOI: 10.1039/d2cp03822f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The combination of nonadiabatic dynamics simulation and optimally tuned range-separated functional might be a powerful tool for elucidating the ultrafast charge transfer in nonfullerene all-small-molecule organic solar cells.
Collapse
Affiliation(s)
- Dan Mao
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, 610068, China
| | - Xin-Rui Chen
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, 610068, China
| | - Dong-Heng Li
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, 610068, China
| | - Xiang-Yang Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, 610068, China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Laicai Li
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, 610068, China
| |
Collapse
|
9
|
Chen WK, Sun XW, Fang Q, Liu XY, Cui GL. GW/BSE nonadiabatic dynamics simulations on excited-state relaxation processes of zinc phthalocyanine-fullerene dyads: Roles of bridging chemical bonds. CHINESE J CHEM PHYS 2021. [DOI: 10.1063/1674-0068/cjcp2109162] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Wen-kai Chen
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Xin-wei Sun
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Qiu Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Xiang-yang Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610068, China
| | - Gang-long Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| |
Collapse
|
10
|
Wanigasekara S, Kattel B, Rudayni F, Chan WL. Extracting Electrons from Delocalized Excitons by Flattening the Energetic Pathway for Charge Separation. J Phys Chem Lett 2021; 12:9047-9054. [PMID: 34516118 DOI: 10.1021/acs.jpclett.1c02228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
At organic donor-acceptor (D-A) interfaces, electron and hole are bound together to form charge transfer (CT) excitons. The electron and hole wave functions in these CT excitons can spatially delocalize. The electron delocalization opens up possibilities of extracting free charges from bound excitons by manipulating the potential energy landscape on the nanoscale. Using a prototype trilayer structure that has a cascade band structure, we show that the yield of charge separation can be doubled as compared to the bilayer counterpart when the thickness of the intermediate layer is around 3 nm. This thickness coincides with the electron delocalization size of CT excitons typically found in these organic films. Tight-binding calculation for the CT states in the trilayer structure further demonstrates that electron delocalization, together with the energy level cascade, can effectively flatten the energetic pathway for charge separation. Hence, it is possible to add nanometer-thick layers between the donor and the acceptor to significantly enhance the charge separation yield.
Collapse
Affiliation(s)
- Shanika Wanigasekara
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Bhupal Kattel
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Fatimah Rudayni
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Wai-Lun Chan
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| |
Collapse
|
11
|
Díaz FR, Duan HG, Miller RJD, Thorwart M. Ultrafast Charge Transfer and Relaxation at a Donor-Acceptor Interface. J Phys Chem B 2021; 125:8869-8875. [PMID: 34319718 DOI: 10.1021/acs.jpcb.1c03595] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The efficiency of charge separation in organic photovoltaic materials is crucially determined by the underlying dynamics of the charge transfer (CT) excitons and their dissociation into free electrons and holes. To unravel the main principles of the underlying mechanism on a molecular level, we construct a toy model of electronically coupled donors interacting with a manifold of CT exciton states. In particular, we set up a ladder of CT site energies to model the exciton dissociation. To mimic the complexity of the exciton dynamics at the donor-acceptor interface, the electronic CT manifold is designed to include two vibrational modes that are vibronically coupled to the excitons. We examine the impact of the electronic and vibrational coherences and the structure of the vibronic manifold on the transfer efficiency and charge recombination. Optimal configurations of the vibronic CT manifold are revealed. In particular, the rate of charge recombination can be minimized when the transient dynamics are carefully explored. Such a toy model can be used as a guide for the design of organic materials for efficient photovoltaic devices.
Collapse
Affiliation(s)
- Fernando Rodríguez Díaz
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2A, 12489 Berlin, Germany.,Nanosystems Institute, Universidad Nacional de San Martín, Av.ËIJ 25 de Mayo 1021, San Martín, Buenos Aires, Argentina
| | - Hong-Guang Duan
- I. Institut für Theoretische Physik, Universität Hamburg, Notkestraße 9, 22607 Hamburg, Germany.,The Hamburg Center for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - R J Dwayne Miller
- Departments of Chemistry and Physics, University of Toronto, 80 St. George Street, Toronto, ON, Canada M5S 3H6
| | - Michael Thorwart
- I. Institut für Theoretische Physik, Universität Hamburg, Notkestraße 9, 22607 Hamburg, Germany.,The Hamburg Center for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
| |
Collapse
|
12
|
Madhu M, Ramakrishnan R, Vijay V, Hariharan M. Free Charge Carriers in Homo-Sorted π-Stacks of Donor-Acceptor Conjugates. Chem Rev 2021; 121:8234-8284. [PMID: 34133137 DOI: 10.1021/acs.chemrev.1c00078] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Inspired by the high photoconversion efficiency observed in natural light-harvesting systems, the hierarchical organization of molecular building blocks has gained impetus in the past few decades. Particularly, the molecular arrangement and packing in the active layer of organic solar cells (OSCs) have garnered significant attention due to the decisive role of the nature of donor/acceptor (D/A) heterojunctions in charge carrier generation and ultimately the power conversion efficiency. This review focuses on the recent developments in emergent optoelectronic properties exhibited by self-sorted donor-on-donor/acceptor-on-acceptor arrangement of covalently linked D-A systems, highlighting the ultrafast excited state dynamics of charge transfer and transport. Segregated organization of donors and acceptors promotes the delocalization of photoinduced charges among the stacks, engendering an enhanced charge separation lifetime and percolation pathways with ambipolar conductivity and charge carrier yield. Covalently linking donors and acceptors ensure a sufficient D-A interface and interchromophoric electronic coupling as required for faster charge separation while providing better control over their supramolecular assemblies. The design strategies to attain D-A conjugate assemblies with optimal charge carrier generation efficiency, the scope of their application compared to state-of-the-art OSCs, current challenges, and future opportunities are discussed in the review. An integrated overview of rational design approaches derived from the comprehension of underlying photoinduced processes can pave the way toward superior optoelectronic devices and bring in new possibilities to the avenue of functional supramolecular architectures.
Collapse
Affiliation(s)
- Meera Madhu
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Vithura, Thiruvananthapuram, Kerala, India 695551
| | - Remya Ramakrishnan
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Vithura, Thiruvananthapuram, Kerala, India 695551
| | - Vishnu Vijay
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Vithura, Thiruvananthapuram, Kerala, India 695551
| | - Mahesh Hariharan
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Vithura, Thiruvananthapuram, Kerala, India 695551
| |
Collapse
|
13
|
Li ZW, Yang JJ, Liu XY, Fang WH, Wang H, Cui G. Chemical Bonding as a New Avenue for Controlling Excited-State Properties and Excitation Energy-Transfer Processes in Zinc Phthalocyanine-Fullerene Dyads. Chemistry 2021; 27:4159-4167. [PMID: 33372312 DOI: 10.1002/chem.202004850] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Indexed: 11/08/2022]
Abstract
Whether chemical bonding can regulate the excited-state and optoelectronic properties of donor-acceptor dyads has been largely elusive. In this work, we used electronic structure and nonadiabatic dynamics methods to explore the excited-state properties of covalently bonded zinc phthalocyanine (ZnPc)-fullerene (C60 ) dyads with a 6-6 (or 5-6) bonding configuration in which ZnPc is bonded to two carbon atoms shared by the two hexagonal rings (or a pentagonal and a hexagonal ring) in C60 . In both cases, the locally excited (LE) states on ZnPc are spectroscopically bright. However, their different chemical bonding differentiates the electronic interactions between ZnPc and C60 . In the 5-6 bonding configuration, the LE states on ZnPc are much higher in energy than the LE states on C60 . Thus, the excitation energy transfer from ZnPc to C60 is thermodynamically favorable. On the other hand, in the 6-6 bonding configuration, such a process is inhibited because the LE states on ZnPc are the lowest ones. More detailed mechanisms are elucidated from nonadiabatic dynamics simulations. In the 6-6 bonding configuration, no excitation energy transfer was observed. In contrast, in the 5-6 bonding configuration, several LE and charge-transfer (CT) excitons were shown to participate in the energy-transfer process. Further analysis reveals that the photoinduced energy transfer is mediated by a CT exciton, such that electron- and hole-transfer processes take place in a concerted but asynchronous manner in the excitation energy transfer. It is also found that high-level electronic structure methods including exciton effects are indispensable to accurately describe photoinduced energy- and electron-transfer processes. Furthermore, this work opens up new avenues for regulating the excited-state properties of molecular donor-acceptor dyads by means of chemical bonding.
Collapse
Affiliation(s)
- Zi-Wen Li
- College of Chemistry, Beijing Normal University, Beijing, 100875, P. R. China
| | - Jia-Jia Yang
- College of Chemistry, Beijing Normal University, Beijing, 100875, P. R. China
| | - Xiang-Yang Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, 610068, P. R. China
| | - Wei-Hai Fang
- College of Chemistry, Beijing Normal University, Beijing, 100875, P. R. China
| | - Haobin Wang
- Department of Chemistry, University of Colorado Denver, Denver, Colorado, 80217-3364, USA
| | - Ganglong Cui
- College of Chemistry, Beijing Normal University, Beijing, 100875, P. R. China
| |
Collapse
|
14
|
Lo MF, Ng TW, Shen D, Lee CS. Charge Energetics and Electronic Level Changes At the Copper(II) Phthalocyanine/Fullerene Junction Upon Photoexcitation. ACS APPLIED MATERIALS & INTERFACES 2020; 12:42992-42996. [PMID: 32845116 DOI: 10.1021/acsami.0c08497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Energy offset at the donor (D)/acceptor (A) interface plays an important role in charge separation in organic photovoltaics. Its magnitude determines the charge separation process under illumination. Extensive studies have been carried out for elucidating the charge transfer (CT) process at different D/A junctions. These works lead to two different views: upon photoexcitation, energies would be (1) consumed in molecular polarization and orientation such that those opposite charges would overcome mutual Coulombic attractive potential at the interface and (2) spent on promoting charges to high-lying delocalized energy states (i.e., hot states), which is necessarily important prior to charge separation. Under these two scheme of studies, the electronic structures and the charge behaviors at the D/A interface should be different under photoexcitation, yet there is so far no direct experimental approach for probing the changes in electronics structures (i.e., Fermi level, vacuum level, frontier molecular orbitals, etc.) upon photoexcitation. Herein, a modified photoelectron spectroscopy (PES) system with an additional solar simulator is used to study the charge distributions and electronic interactions for a standard D/A heterojunction (i.e., copper phthalocyanine (CuPc)/ fullerene (C60)) under photoexcitation. CT states formed as a result of photon energy transfer at the CuPc/C60 junction. Subsequent superpositions of charge transfer and electron polarization effects increase the D/A energy level offsets from 0.75 (ground state measured in the dark) to 1.07 eV (high-lying state measured upon illumination). We showed that there is excess energy consumed for a subtle change in the energy level alignment of the CuPc/C60 junction under illumination, suggesting a new insight for the energy loss mechanism during the photocharge generation processes.
Collapse
Affiliation(s)
- Ming-Fai Lo
- Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, Hong Kong SAR, P. R. China
- City University of Hong Kong Shenzhen Research Institute, Shenzhen 518000, P. R. China
| | - Tsz-Wai Ng
- Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, Hong Kong SAR, P. R. China
- City University of Hong Kong Shenzhen Research Institute, Shenzhen 518000, P. R. China
| | - Dong Shen
- Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, Hong Kong SAR, P. R. China
| | - Chun-Sing Lee
- Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, Hong Kong SAR, P. R. China
- City University of Hong Kong Shenzhen Research Institute, Shenzhen 518000, P. R. China
| |
Collapse
|
15
|
Rijal K, Rudayni F, Kafle TR, Chan WL. Collective Effects of Band Offset and Wave Function Dimensionality on Impeding Electron Transfer from 2D to Organic Crystals. J Phys Chem Lett 2020; 11:7495-7501. [PMID: 32812767 DOI: 10.1021/acs.jpclett.0c01796] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Excited-state electron transfer (ET) across molecules/transition metal dichalcogenide crystal (TMDC) interfaces is a critical process for the functioning of various organic/TMDC hybrid optoelectronic devices. Therefore, it is important to understand the fundamental factors that can facilitate or limit the ET rate. Here it is found that an undesirable combination of the interfacial band offset and the spatial dimensionality of the delocalized electron wave function can significantly slow down the ET process. Specifically, it is found that whereas the ET rate from TMDCs (MoS2 and WSe2) to fullerenes is relative insensitive to the band offset, the ET rate from TMDCs to perylene molecules can be reduced by an order of magnitude when the band offset is large. For the perylene crystal, the sensitivity of the ET rate on the band offset is explained by the 1D nature of the electronic wave function, which limits the availability of states with the appropriate energy to accept the electron.
Collapse
Affiliation(s)
- Kushal Rijal
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Fatimah Rudayni
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Tika R Kafle
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Wai-Lun Chan
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| |
Collapse
|
16
|
Liu XY, Li ZW, Fang WH, Cui G. Nonadiabatic Exciton and Charge Separation Dynamics at Interfaces of Zinc Phthalocyanine and Fullerene: Orientation Does Matter. J Phys Chem A 2020; 124:7388-7398. [DOI: 10.1021/acs.jpca.0c05865] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xiang-Yang Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610068, P. R. China
| | - Zi-Wen Li
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Wei-Hai Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| |
Collapse
|
17
|
|
18
|
Kafle TR, Kattel B, Yao P, Zereshki P, Zhao H, Chan WL. Effect of the Interfacial Energy Landscape on Photoinduced Charge Generation at the ZnPc/MoS 2 Interface. J Am Chem Soc 2019; 141:11328-11336. [PMID: 31259543 DOI: 10.1021/jacs.9b05893] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Monolayer transition-metal dichalcogenide crystals (TMDC) can be combined with other functional materials, such as organic molecules, to form a wide range of heterostructures with tailorable properties. Although a number of works have shown that ultrafast charge transfer (CT) can occur at organic/TMDC interfaces, conditions that would facilitate the separation of interfacial CT excitons into free carriers remain unclear. Here, time-resolved and steady-state photoemission spectroscopy are used to study the potential energy landscape, charge transfer, and exciton dynamics at the zinc phthalocyanine (ZnPc)/monolayer (ML) MoS2 and ZnPc/bulk MoS2 interfaces. Surprisingly, although both interfaces have a type-II band alignment and exhibit sub-100 fs CT, the CT excitons formed at the two interfaces show drastically different evolution dynamics. The ZnPc/ML-MoS2 behaves like typical donor-acceptor interfaces in which CT excitons dissociate into electron-hole pairs. On the contrary, back electron transfer occur at ZnPc/bulk-MoS2, which results in the formation of triplet excitons in ZnPc. The difference can be explained by the different amount of band bending found in the ZnPc film deposited on ML-MoS2 and bulk-MoS2. Our work illustrates that the potential energy landscape near the interface plays an important role in the charge separation behavior. Therefore, considering the energy level alignment at the interface alone is not enough for predicting whether free charges can be generated effectively from an interface.
Collapse
Affiliation(s)
- Tika R Kafle
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Bhupal Kattel
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Peng Yao
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States.,Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology , Beijing Jiaotong University , Beijing 100044 , China
| | - Peymon Zereshki
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Hui Zhao
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Wai-Lun Chan
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| |
Collapse
|
19
|
Zhao ZW, Duan YC, Pan QQ, Gao Y, Wu Y, Geng Y, Zhao L, Zhang M, Su ZM. A probe into underlying factors affecting utrafast charge transfer at Donor/IDIC interface of all-small-molecule nonfullerene organic solar cells. J Photochem Photobiol A Chem 2019. [DOI: 10.1016/j.jphotochem.2019.02.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
20
|
Dimitrov SD, Azzouzi M, Wu J, Yao J, Dong Y, Tuladhar PS, Schroeder BC, Bittner ER, McCulloch I, Nelson J, Durrant JR. Spectroscopic Investigation of the Effect of Microstructure and Energetic Offset on the Nature of Interfacial Charge Transfer States in Polymer: Fullerene Blends. J Am Chem Soc 2019; 141:4634-4643. [PMID: 30807130 PMCID: PMC6429453 DOI: 10.1021/jacs.8b11484] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Despite
performance improvements of organic photovoltaics, the
mechanism of photoinduced electron–hole separation at organic
donor–acceptor interfaces remains poorly understood. Inconclusive
experimental and theoretical results have produced contradictory models
for electron–hole separation in which the role of interfacial
charge-transfer (CT) states is unclear, with one model identifying
them as limiting separation and another as readily dissociating. Here,
polymer–fullerene blends with contrasting photocurrent properties
and enthalpic offsets driving separation were studied. By modifying
composition, film structures were varied from consisting of molecularly
mixed polymer–fullerene domains to consisting of both molecularly
mixed and fullerene domains. Transient absorption spectroscopy revealed
that CT state dissociation generating separated electron–hole
pairs is only efficient in the high energy offset blend with fullerene
domains. In all other blends (with low offset or predominantly molecularly
mixed domains), nanosecond geminate electron–hole recombination
is observed revealing the importance of spatially localized electron–hole
pairs (bound CT states) in the electron–hole dynamics. A two-dimensional
lattice exciton model was used to simulate the excited state spectrum
of a model system as a function of microstructure and energy offset.
The results could reproduce the main features of experimental electroluminescence
spectra indicating that electron–hole pairs become less bound
and more spatially separated upon increasing energy offset and fullerene
domain density. Differences between electroluminescence and photoluminescence
spectra could be explained by CT photoluminescence being dominated
by more-bound states, reflecting geminate recombination processes,
while CT electroluminescence preferentially probes less-bound CT states
that escape geminate recombination. These results suggest that apparently
contradictory studies on electron–hole separation can be explained
by the presence of both bound and unbound CT states in the same film,
as a result of a range of interface structures.
Collapse
Affiliation(s)
- S D Dimitrov
- SPECIFIC, College of Engineering , Swansea University , Bay Campus , Swansea SA1 8EN , United Kingdom
| | | | | | | | | | | | - B C Schroeder
- Department of Chemistry , University College , London WC1H 0AJ , United Kingdom
| | - E R Bittner
- Department of Chemistry , University of Houston , Houston , Texas 77204 , United States
| | - I McCulloch
- Physical Sciences and Engineering Division, KAUST Solar Center (KSC) , King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900 , Kingdom of Saudi Arabia
| | | | - J R Durrant
- SPECIFIC, College of Engineering , Swansea University , Bay Campus , Swansea SA1 8EN , United Kingdom
| |
Collapse
|
21
|
Kafle TR, Kattel B, Wang T, Chan WL. The relationship between the coherent size, binding energy and dissociation dynamics of charge transfer excitons at organic interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:454001. [PMID: 30265252 DOI: 10.1088/1361-648x/aae50b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
At organic semiconductor interfaces, an electron and a hole can be bound Coulombically to form an interfacial charge transfer (CT) exciton. It is still under debate how a CT exciton can overcome its strong binding and dissociate into free carriers. Experimentally, capturing the evolution of the CT exciton on time (fs-ps) and length scales (nm) in which the dissociation process occurs is challenging. To overcome this challenge, time-resolved two photon photoemission spectroscopy is used to measure the binding energies and electronic coherent sizes of a series of CT states at organic interfaces, and capture the temporal dynamics of these CT excitons after their excitation. Using zinc phthalocyanine (ZnPc)/fullerene (C60) interface as a model system, it is shown that the interfacial CT process first populates a hot CT state with a coherent size of ~4 nm. Hot and delocalized CT excitons subsequently relax into CT excitons with lower energies and smaller coherent sizes. To correlate the CT exciton properties with the dissociation efficiency, we develop a method that exploits graphene field effect transistors to probe the rate and yield of free carrier generation at the interface. Our results show that exciton dissociation can be more efficient if one can extract electrons from the hot and delocalized CT state. We propose a cascade structure that would serve this purpose.
Collapse
Affiliation(s)
- Tika R Kafle
- Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045, United States of America
| | | | | | | |
Collapse
|
22
|
Kataeva O, Metlushka K, Ivshin K, Kiiamov A, Alfonsov V, Khrizanforov M, Budnikova Y, Sinyashin O, Krupskaya Y, Kataev V, Büchner B, Knupfer M. Electron Transfer and Unusual Chemical Transformations of F4-TCNQ in a Reaction with Mn-Phthalocyanine. Eur J Inorg Chem 2018. [DOI: 10.1002/ejic.201800641] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Olga Kataeva
- A. E. Arbuzov Institute of Organic and Physical Chemistry; FRC Kazan Scientific Center; Russian Academy of Sciences; Arbuzov str. 8 420088 Kazan Russia
| | - Kirill Metlushka
- A. E. Arbuzov Institute of Organic and Physical Chemistry; FRC Kazan Scientific Center; Russian Academy of Sciences; Arbuzov str. 8 420088 Kazan Russia
- A. M. Butlerov Chemistry Institute of the Kazan Federal University; Kremlevskaya str. 18 420008 Kazan Russia
| | - Kamil Ivshin
- A. E. Arbuzov Institute of Organic and Physical Chemistry; FRC Kazan Scientific Center; Russian Academy of Sciences; Arbuzov str. 8 420088 Kazan Russia
- A. M. Butlerov Chemistry Institute of the Kazan Federal University; Kremlevskaya str. 18 420008 Kazan Russia
| | - Airat Kiiamov
- Institute of Physics; Kazan Federal University; Kremlevskaya str. 18 420008 Kazan Russia
| | - Vladimir Alfonsov
- A. E. Arbuzov Institute of Organic and Physical Chemistry; FRC Kazan Scientific Center; Russian Academy of Sciences; Arbuzov str. 8 420088 Kazan Russia
- A. M. Butlerov Chemistry Institute of the Kazan Federal University; Kremlevskaya str. 18 420008 Kazan Russia
| | - Mikhail Khrizanforov
- A. E. Arbuzov Institute of Organic and Physical Chemistry; FRC Kazan Scientific Center; Russian Academy of Sciences; Arbuzov str. 8 420088 Kazan Russia
| | - Yulia Budnikova
- A. E. Arbuzov Institute of Organic and Physical Chemistry; FRC Kazan Scientific Center; Russian Academy of Sciences; Arbuzov str. 8 420088 Kazan Russia
| | - Oleg Sinyashin
- A. E. Arbuzov Institute of Organic and Physical Chemistry; FRC Kazan Scientific Center; Russian Academy of Sciences; Arbuzov str. 8 420088 Kazan Russia
| | - Yulia Krupskaya
- Institute for Solid State and Materials Research IFW Dresden; Helmholtz str. 20 01069 Dresden Germany
| | - Vladislav Kataev
- Institute for Solid State and Materials Research IFW Dresden; Helmholtz str. 20 01069 Dresden Germany
| | - Bernd Büchner
- Institute for Solid State and Materials Research IFW Dresden; Helmholtz str. 20 01069 Dresden Germany
- Institut für Feskörper- und Materialphysik; Technische Universität Dresden; 01062 Dresden Germany
| | - Martin Knupfer
- Institute for Solid State and Materials Research IFW Dresden; Helmholtz str. 20 01069 Dresden Germany
| |
Collapse
|
23
|
Wu Q, Zhao D, Goldey MB, Filatov AS, Sharapov V, Colón YJ, Cai Z, Chen W, de Pablo J, Galli G, Yu L. Intra-molecular Charge Transfer and Electron Delocalization in Non-fullerene Organic Solar Cells. ACS APPLIED MATERIALS & INTERFACES 2018; 10:10043-10052. [PMID: 29498504 DOI: 10.1021/acsami.7b18717] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Two types of electron acceptors were synthesized by coupling two kinds of electron-rich cores with four equivalent perylene diimides (PDIs) at the α-position. With fully aromatic cores, TPB and TPSe have π-orbitals spread continuously over the whole aromatic conjugated backbone, unlike TPC and TPSi, which contain isolated PDI units due to the use of a tetrahedron carbon or silicon linker. Density functional theory calculations of the projected density of states showed that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) for TPB are localized in separate regions of space. Further, the LUMO of TPB shows a greater contribution from the orbitals belonging to the connective core of the molecules than that of TPC. Overall, the properties of the HOMO and LUMO point at increased intra-molecular delocalization of negative charge carriers for TPB and TPSe than for TPC and TPSi and hence at a more facile intra-molecular charge transfer for the former. The film absorption and emission spectra showed evidences for the inter-molecular electron delocalization in TPB and TPSe, which is consistent with the network structure revealed by X-ray diffraction studies on single crystals of TPB. These features benefit the formation of charge transfer states and/or facilitate charge transport. Thus, higher electron mobility and higher charge dissociation probabilities under Jsc condition were observed in blend films of TPB:PTB7-Th and TPSe:PTB7-Th than those in TPC:PTB7-Th and TPSi:PTB7-Th blend films. As a result, the Jsc and fill factor values of 15.02 mA/cm2, 0.58 and 14.36 mA/cm2, 0.55 for TPB- and TPSe-based solar cell are observed, whereas those for TPC and TPSi are 11.55 mA/cm2, 0.47 and 10.35 mA/cm2, 0.42, respectively.
Collapse
Affiliation(s)
- Qinghe Wu
- Department of Chemistry, Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province , Shantou University , Guangdong 515063 , P. R. China
| | - Donglin Zhao
- Department of Chemistry, The James Franck Institute , The University of Chicago , 929 E 57th Street , Chicago , Illinois 60637 , United States
| | - Matthew B Goldey
- Institute for Molecular Engineering , The University of Chicago , 5747 South Ellis Avenue , Chicago , Illinois 60637 , United States
| | - Alexander S Filatov
- Department of Chemistry, The James Franck Institute , The University of Chicago , 929 E 57th Street , Chicago , Illinois 60637 , United States
| | - Valerii Sharapov
- Department of Chemistry, The James Franck Institute , The University of Chicago , 929 E 57th Street , Chicago , Illinois 60637 , United States
| | - Yamil J Colón
- Institute for Molecular Engineering, Materials Science Division , Argonne National Laboratory , 9700 Cass Avenue , Lemont , Illinois 60439 , United States
- Institute for Molecular Engineering , The University of Chicago , 5747 South Ellis Avenue , Chicago , Illinois 60637 , United States
| | - Zhengxu Cai
- Department of Chemistry, The James Franck Institute , The University of Chicago , 929 E 57th Street , Chicago , Illinois 60637 , United States
| | - Wei Chen
- Institute for Molecular Engineering, Materials Science Division , Argonne National Laboratory , 9700 Cass Avenue , Lemont , Illinois 60439 , United States
- Institute for Molecular Engineering , The University of Chicago , 5747 South Ellis Avenue , Chicago , Illinois 60637 , United States
| | - Juan de Pablo
- Institute for Molecular Engineering, Materials Science Division , Argonne National Laboratory , 9700 Cass Avenue , Lemont , Illinois 60439 , United States
- Institute for Molecular Engineering , The University of Chicago , 5747 South Ellis Avenue , Chicago , Illinois 60637 , United States
| | - Giulia Galli
- Institute for Molecular Engineering, Materials Science Division , Argonne National Laboratory , 9700 Cass Avenue , Lemont , Illinois 60439 , United States
- Institute for Molecular Engineering , The University of Chicago , 5747 South Ellis Avenue , Chicago , Illinois 60637 , United States
| | - Luping Yu
- Department of Chemistry, The James Franck Institute , The University of Chicago , 929 E 57th Street , Chicago , Illinois 60637 , United States
| |
Collapse
|
24
|
Rozzi CA, Troiani F, Tavernelli I. Quantum modeling of ultrafast photoinduced charge separation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:013002. [PMID: 29047450 DOI: 10.1088/1361-648x/aa948a] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Phenomena involving electron transfer are ubiquitous in nature, photosynthesis and enzymes or protein activity being prominent examples. Their deep understanding thus represents a mandatory scientific goal. Moreover, controlling the separation of photogenerated charges is a crucial prerequisite in many applicative contexts, including quantum electronics, photo-electrochemical water splitting, photocatalytic dye degradation, and energy conversion. In particular, photoinduced charge separation is the pivotal step driving the storage of sun light into electrical or chemical energy. If properly mastered, these processes may also allow us to achieve a better command of information storage at the nanoscale, as required for the development of molecular electronics, optical switching, or quantum technologies, amongst others. In this Topical Review we survey recent progress in the understanding of ultrafast charge separation from photoexcited states. We report the state-of-the-art of the observation and theoretical description of charge separation phenomena in the ultrafast regime mainly focusing on molecular- and nano-sized solar energy conversion systems. In particular, we examine different proposed mechanisms driving ultrafast charge dynamics, with particular regard to the role of quantum coherence and electron-nuclear coupling, and link experimental observations to theoretical approaches based either on model Hamiltonians or on first principles simulations.
Collapse
|
25
|
Kafle TR, Kattel B, Lane SD, Wang T, Zhao H, Chan WL. Charge Transfer Exciton and Spin Flipping at Organic-Transition-Metal Dichalcogenide Interfaces. ACS NANO 2017; 11:10184-10192. [PMID: 28985468 DOI: 10.1021/acsnano.7b04751] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Two-dimensional transition-metal dichalcogenides (TMD) can be combined with other materials such as organic small molecules to form hybrid van der Waals heterostructures. Because of different properties possessed by these two materials, the hybrid interface can exhibit properties that cannot be found in either of the materials. In this work, the zinc phthalocyanine (ZnPc)-molybdenum disulfide (MoS2) interface is used as a model system to study the charge transfer at these interfaces. It is found that the optically excited singlet exciton in ZnPc transfers its electron to MoS2 in 80 fs after photoexcitation to form a charge transfer exciton. However, back electron transfer occurs on the time scale of ∼1-100 ps, which results in the formation of a triplet exciton in the ZnPc layer. This relatively fast singlet-triplet transition is feasible because of the large singlet-triplet splitting in organic materials and the strong spin-orbit coupling in TMD crystals. The back electron transfer would reduce the yield of free carrier generation at the heterojunction if it is not avoided. On the other hand, the spin-selective back electron transfer could be used to manipulate electron spin in hybrid electronic devices.
Collapse
Affiliation(s)
- Tika R Kafle
- Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States
| | - Bhupal Kattel
- Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States
| | - Samuel D Lane
- Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States
| | - Ti Wang
- Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States
| | - Hui Zhao
- Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States
| | - Wai-Lun Chan
- Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States
| |
Collapse
|
26
|
Geng Y, Lee MH, Troisi A. Effect of Infrared Pulse Excitation on the Bound Charge-Transfer State of Photovoltaic Interfaces. J Phys Chem Lett 2017; 8:4872-4877. [PMID: 28927273 DOI: 10.1021/acs.jpclett.7b02088] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The nature and dynamics of the bound charge-transfer (CT) state in the exciton dissociation process in organic solar cells are of critical importance for the understanding of these devices. It was recently demonstrated that this state can be probed by a new experiment in which an infrared (IR) push-pulse is used to dissociate charges from the bound excited state. Here we proposed a simple quantum dynamics model to simulate the excitation of the IR pulse on the bound CT state with model parameters extracted from quantum chemical calculations. We show that the pulse dissociates the CT state following two different mechanisms: one, fairly expected, is the direct excitation of higher energy CT states leading to charge separation; the other, proposed here for the first time, is a rebound mechanism in which the negative charge is transferred in the opposite direction to form the neutral Frenkel exciton state from where it dissociates.
Collapse
Affiliation(s)
- Yun Geng
- Department of Chemistry, University of Warwick , Coventry CV4 7AL, U.K
- Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University , Changchun 130024, P.R. China
| | - Myeong H Lee
- Department of Chemistry, University of Warwick , Coventry CV4 7AL, U.K
- Department of Chemistry, University of Liverpool , Liverpool L69 7ZD, U.K
| | - Alessandro Troisi
- Department of Chemistry, University of Liverpool , Liverpool L69 7ZD, U.K
| |
Collapse
|
27
|
Lim H, Kwon H, Kim SK, Kim JW. Delayed Triplet-State Formation through Hybrid Charge Transfer Exciton at Copper Phthalocyanine/GaAs Heterojunction. J Phys Chem Lett 2017; 8:4763-4768. [PMID: 28914058 DOI: 10.1021/acs.jpclett.7b02111] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Light absorption in organic molecules on an inorganic substrate and subsequent electron transfer to the substrate create so-called hybrid charge transfer exciton (HCTE). The relaxation process of the HCTE states largely determines charge separation efficiency or optoelectronic device performance. Here, the study on energy and time-dispersive behavior of photoelectrons at the hybrid interface of copper phthalocyanine (CuPc)/p-GaAs(001) upon light excitation of GaAs reveals a clear pathway for HCTE relaxation and delayed triplet-state formation. According to the ground-state energy level alignment at the interface, CuPc/p-GaAs(001) shows initially fast hole injection from GaAs to CuPc. Thus, the electrons in GaAs and holes in CuPc form an unusual HCTE state manifold. Subsequent electron transfer from GaAs to CuPc generates the formation of the triplet state in CuPc with a few picoseconds delay. Such two-step charge transfer causes delayed triplet-state formation without singlet excitation and subsequent intersystem crossing within the CuPc molecules.
Collapse
Affiliation(s)
- Heeseon Lim
- Department of Chemistry, KAIST , 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea
- Korea Research Institute of Standards and Science , 267 Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea
| | - Hyuksang Kwon
- Korea Research Institute of Standards and Science , 267 Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea
| | - Sang Kyu Kim
- Department of Chemistry, KAIST , 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea
| | - Jeong Won Kim
- Korea Research Institute of Standards and Science , 267 Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea
| |
Collapse
|
28
|
Ponseca CS, Chábera P, Uhlig J, Persson P, Sundström V. Ultrafast Electron Dynamics in Solar Energy Conversion. Chem Rev 2017; 117:10940-11024. [DOI: 10.1021/acs.chemrev.6b00807] [Citation(s) in RCA: 211] [Impact Index Per Article: 30.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Carlito S. Ponseca
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Pavel Chábera
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Jens Uhlig
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Petter Persson
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Villy Sundström
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| |
Collapse
|