201
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Dipole analyses for short-circuit current in organic photovoltaic devices of diketopyrrolopyrrole-based donor and PCBM. Theor Chem Acc 2016. [DOI: 10.1007/s00214-016-1875-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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202
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Yang QD, Li HW, Cheng Y, Guan Z, Liu T, Ng TW, Lee CS, Tsang SW. Probing the Energy Level Alignment and the Correlation with Open-Circuit Voltage in Solution-Processed Polymeric Bulk Heterojunction Photovoltaic Devices. ACS APPLIED MATERIALS & INTERFACES 2016; 8:7283-7290. [PMID: 26926667 DOI: 10.1021/acsami.5b11395] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Energy level alignment at the organic donor and acceptor interface is a key to determine the photovoltaic performance in organic solar cells, but direct probing of such energy alignment is still challenging especially for solution-processed bulk heterojunction (BHJ) thin films. Here we report a systematic investigation on probing the energy level alignment with different approaches in five commonly used polymer:[6,6]-phenyl-C71-butyric acid methyl ester (PCBM) BHJ systems. We find that by tuning the weight ratio of polymer to PCBM the electronic features from both polymer and PCBM can be obtained by photoemission spectroscopy. Using this approach, we find that some of the BHJ blends simply follow vacuum level alignment, but others show strong energy level shifting as a result of Fermi level pinning. Independently, by measuring the temperature-dependent open-circuit voltage (VOC), we find that the effective energy gap (Eeff), the energy difference between the highest occupied molecular orbital of the polymer donor (EHOMO-D) and lowest unoccupied molecular orbital of the PCBM acceptor (ELUMO-A), obtained by photoemission spectroscopy in all polymer:PCBM blends has an excellent agreement with the extrapolated VOC at 0 K. Consequently, the photovoltage loss of various organic BHJ photovoltaic devices at room temperature is in a range of 0.3-0.6 V. It is believed that the demonstrated direct measurement approach of the energy level alignment in solution-processed organic BHJ will bring deeper insight into the origin of the VOC and the corresponding photovoltage loss mechanism in organic photovoltaic cells.
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Affiliation(s)
- Qing-Dan Yang
- Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China
- Department of Physics and Materials Science, Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong , Hong Kong SAR, P. R. China
| | - Ho-Wa Li
- Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China
| | - Yuanhang Cheng
- Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China
| | - Zhiqiang Guan
- Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China
- Department of Physics and Materials Science, Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong , Hong Kong SAR, P. R. China
| | - Taili Liu
- Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China
| | - Tsz-Wai Ng
- Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China
- Department of Physics and Materials Science, Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong , Hong Kong SAR, P. R. China
| | - Chun-Sing Lee
- Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China
- Department of Physics and Materials Science, Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong , Hong Kong SAR, P. R. China
| | - Sai-Wing Tsang
- Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China
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203
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Fazzi D, Barbatti M, Thiel W. Unveiling the Role of Hot Charge-Transfer States in Molecular Aggregates via Nonadiabatic Dynamics. J Am Chem Soc 2016; 138:4502-11. [DOI: 10.1021/jacs.5b13210] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Daniele Fazzi
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Mario Barbatti
- Aix Marseille Université, CNRS, ICR UMR7273, 13397 Marseille, France
| | - Walter Thiel
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
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204
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Manaka T, Iwamoto M. Optical second-harmonic generation measurement for probing organic device operation. LIGHT, SCIENCE & APPLICATIONS 2016; 5:e16040. [PMID: 30167147 PMCID: PMC6059894 DOI: 10.1038/lsa.2016.40] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 11/11/2015] [Accepted: 11/12/2015] [Indexed: 05/15/2023]
Abstract
We give a brief overview of the electric-field induced optical second-harmonic generation (EFISHG) technique that has been used to study the complex behaviors of organic-based devices. By analyzing EFISHG images of organic field-effect transistors, the in-plane two-dimensional distribution of the electric field in the channel can be evaluated. The susceptibility tensor of the organic semiconductor layer and the polarization of the incident light are considered to determine the electric field distribution. EFISHG imaging can effectively evaluate the distribution of the vectorial electric field in organic films by selecting a light polarization. With the time-resolved technique, measurement of the electric field originating from the injected carriers allows direct probing of the carrier motion under device operation, because the transient change of the electric field distribution reflects the carrier motion. Some applications of the EFISHG technique to organic electronic devices are reviewed.
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Affiliation(s)
- Takaaki Manaka
- Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Mitsumasa Iwamoto
- Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
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205
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Song P, Li Y, Ma F, Pullerits T, Sun M. Photoinduced Electron Transfer in Organic Solar Cells. CHEM REC 2016; 16:734-53. [PMID: 26853631 DOI: 10.1002/tcr.201500244] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Indexed: 11/07/2022]
Abstract
Electron transfer (ET) is the key process in light-driven charge separation reactions in organic solar cells. The current review summarizes the progress in theoretical modelling of ET in these materials. First we give an account of ET, with a description originating from Marcus theory. We systematically go through all the relevant parameters and show how they depend on different material properties, and discuss the consequences such dependencies have for the performance of the devices. Finally, we present a set of visualization methods which have proven to be very useful in analyzing the elementary processes in absorption and charge separation events. Such visualization tools help us to understand the properties of the photochemical and photobiological systems in solar cells.
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Affiliation(s)
- Peng Song
- Department of Physics, Liaoning University, Shenyang, 110036, P. R. China.,Beijing National Laboratory for Condensed Matter Physics, Institute of Physics Chinese Academy of Science, Beijing, 100190, P. R. China.,State Key laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics Chinese Academy of Science, Dalian, 116023, P. R. China
| | - Yuanzuo Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics Chinese Academy of Science, Beijing, 100190, P. R. China.,College of Science, Northeast Forestry University, Harbin, 150040, P. R. China
| | - Fengcai Ma
- Department of Physics, Liaoning University, Shenyang, 110036, P. R. China
| | - Tõnu Pullerits
- Department of Chemical Physics, Lund University, Box 124, Lund, 22100, Sweden.,State Key laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics Chinese Academy of Science, Dalian, 116023, P. R. China
| | - Mengtao Sun
- Department of Physics, Liaoning University, Shenyang, 110036, P. R. China.,Beijing National Laboratory for Condensed Matter Physics, Institute of Physics Chinese Academy of Science, Beijing, 100190, P. R. China
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206
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D'Avino G, Muccioli L, Olivier Y, Beljonne D. Charge Separation and Recombination at Polymer-Fullerene Heterojunctions: Delocalization and Hybridization Effects. J Phys Chem Lett 2016; 7:536-40. [PMID: 26785294 DOI: 10.1021/acs.jpclett.5b02680] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
We address charge separation and recombination in polymer/fullerene solar cells with a multiscale modeling built from accurate atomistic inputs and accounting for disorder, interface electrostatics and genuine quantum effects on equal footings. Our results show that bound localized charge transfer states at the interface coexist with a large majority of thermally accessible delocalized space-separated states that can be also reached by direct photoexcitation, thanks to their strong hybridization with singlet polymer excitons. These findings reconcile the recent experimental reports of ultrafast exciton separation ("hot" process) with the evidence that high quantum yields do not require excess electronic or vibrational energy ("cold" process), and show that delocalization, by shifting the density of charge transfer states toward larger effective electron-hole radii, may reduce energy losses through charge recombination.
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Affiliation(s)
- Gabriele D'Avino
- Laboratory for Chemistry of Novel Materials, University of Mons , 7000 Mons, Belgium
| | - Luca Muccioli
- Laboratoire de Chimie des Polymères Organiques, UMR 5629, University of Bordeaux , 33607 Pessac, France
| | - Yoann Olivier
- Laboratory for Chemistry of Novel Materials, University of Mons , 7000 Mons, Belgium
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons , 7000 Mons, Belgium
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207
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Bittner ER, Kelley A. The role of structural fluctuations and environmental noise in the electron/hole separation kinetics at organic polymer bulk-heterojunction interfaces. Phys Chem Chem Phys 2016; 17:28853-9. [PMID: 26449151 DOI: 10.1039/c5cp05037e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
We investigate the electronic dynamics of a model organic photovoltaic (OPV) system consisting of polyphenylene vinylene (PPV) oligomers and a [6,6]-phenyl C61-butyric acid methylester (PCBM) blend using a mixed molecular mechanics/quantum mechanics (MM/QM) approach. Using a heuristic model that connects energy gap fluctuations to the average electronic couplings and decoherence times, we provide an estimate of the state-to-state internal conversion rates within the manifold of the lowest few electronic excitations. We find that the lowest few excited states of a model interface are rapidly mixed by C[double bond, length as m-dash]C bond fluctuations such that the system can sample both intermolecular charge-transfer and charge-separated electronic configurations on a time scale of 20 fs. Our simulations support an emerging picture of carrier generation in OPV systems in which interfacial electronic states can rapidly decay into charge-separated and current producing states via coupling to vibronic degrees of freedom.
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Affiliation(s)
- Eric R Bittner
- Department of Chemistry and Centre for Quantum Engineering, University of Houston, Houston, TX 77204, USA.
| | - Allen Kelley
- Department of Chemistry and Centre for Quantum Engineering, University of Houston, Houston, TX 77204, USA.
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208
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Cunningham PD, Lane PA, Melinger JS, Esenturk O, Heilweil EJ. Probing Charge Transfer and Hot Carrier Dynamics in Organic Solar Cells with Terahertz Spectroscopy. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2016. [PMID: 28649166 DOI: 10.1117/12.2228379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Time-resolved terahertz spectroscopy (TRTS) was used to explore charge generation, transfer, and the role of hot carriers in organic solar cell materials. Two model molecular photovoltaic systems were investigated: with zinc phthalocyanine (ZnPc) or alpha-sexathiophene (α-6T) as the electron donors and buckminsterfullerene (C60) as the electron acceptor. TRTS provides charge carrier conductivity dynamics comprised of changes in both population and mobility. By using time-resolved optical spectroscopy in conjunction with TRTS, these two contributions can be disentangled. The sub-picosecond photo-induced conductivity decay dynamics of C60 were revealed to be caused by auto-ionization: the intrinsic process by which charge is generated in molecular solids. In donor-acceptor blends, the long-lived photo-induced conductivity is used for weight fraction optimization of the constituents. In nanoscale multilayer films, the photo-induced conductivity identifies optimal layer thicknesses. In films of ZnPc/C60, electron transfer from ZnPc yields hot charges that localize and become less mobile as they thermalize. Excitation of high-lying Franck Condon states in C60 followed by hole-transfer to ZnPc similarly produces hot charge carriers that self-localize; charge transfer clearly precedes carrier cooling. This picture is contrasted to charge transfer in α-6T/C60, where hole transfer takes place from a thermalized state and produces equilibrium carriers that do not show characteristic signs of cooling and self-localization. These results illustrate the value of terahertz spectroscopic methods for probing charge transfer reactions.
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Affiliation(s)
| | - Paul A Lane
- U.S. Naval Research Laboratory, Washington, DC 20375, United States
| | | | - Okan Esenturk
- Chemistry Department, Middle East Technical University, Ankara, Turkey
| | - Edwin J Heilweil
- National Institute of Standards and Technology, Gaithersburg, MD 20899, United States
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209
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Ruchira Silva W, Frontiera RR. Excited state structural evolution during charge-transfer reactions in betaine-30. Phys Chem Chem Phys 2016; 18:20290-7. [DOI: 10.1039/c5cp06195d] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ultrafast photo-induced charge-transfer reactions are fundamental to a number of photovoltaic and photocatalytic devices, yet the multidimensional nature of the reaction coordinate makes these processes difficult to model theoretically.
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210
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Shimazaki T, Nakajima T. Application of the dielectric-dependent screened exchange potential approach to organic photocell materials. Phys Chem Chem Phys 2016; 18:27554-27563. [DOI: 10.1039/c6cp04863c] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
This paper discusses the fundamental features of the dielectric-dependent screened exchange potential approach for organic molecules and photocell materials.
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211
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Higashino T, Yamada T, Yamamoto M, Furube A, Tkachenko NV, Miura T, Kobori Y, Jono R, Yamashita K, Imahori H. Remarkable Dependence of the Final Charge Separation Efficiency on the Donor-Acceptor Interaction in Photoinduced Electron Transfer. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201509067] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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212
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Higashino T, Yamada T, Yamamoto M, Furube A, Tkachenko NV, Miura T, Kobori Y, Jono R, Yamashita K, Imahori H. Remarkable Dependence of the Final Charge Separation Efficiency on the Donor-Acceptor Interaction in Photoinduced Electron Transfer. Angew Chem Int Ed Engl 2015; 55:629-33. [DOI: 10.1002/anie.201509067] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Revised: 11/04/2015] [Indexed: 11/12/2022]
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213
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Deotare PB, Chang W, Hontz E, Congreve DN, Shi L, Reusswig PD, Modtland B, Bahlke ME, Lee CK, Willard AP, Bulović V, Van Voorhis T, Baldo MA. Nanoscale transport of charge-transfer states in organic donor-acceptor blends. NATURE MATERIALS 2015; 14:1130-4. [PMID: 26413986 DOI: 10.1038/nmat4424] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 08/14/2015] [Indexed: 05/13/2023]
Abstract
Charge-transfer (CT) states, bound combinations of an electron and a hole on separate molecules, play a crucial role in organic optoelectronic devices. We report direct nanoscale imaging of the transport of long-lived CT states in molecular organic donor-acceptor blends, which demonstrates that the bound electron-hole pairs that form the CT states move geminately over distances of 5-10 nm, driven by energetic disorder and diffusion to lower energy sites. Magnetic field dependence reveals a fluctuating exchange splitting, indicative of a variation in electron-hole spacing during diffusion. The results suggest that the electron-hole pair of the CT state undergoes a stretching transport mechanism analogous to an 'inchworm' motion, in contrast to conventional transport of Frenkel excitons. Given the short exciton lifetimes characteristic of bulk heterojunction organic solar cells, this work confirms the potential importance of CT state transport, suggesting that CT states are likely to diffuse farther than Frenkel excitons in many donor-acceptor blends.
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Affiliation(s)
- P B Deotare
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - W Chang
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - E Hontz
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - D N Congreve
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - L Shi
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - P D Reusswig
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - B Modtland
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - M E Bahlke
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - C K Lee
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - A P Willard
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - V Bulović
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - T Van Voorhis
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - M A Baldo
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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214
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de Gier HD, Jahani F, Broer R, Hummelen JC, Havenith RWA. Promising Strategy To Improve Charge Separation in Organic Photovoltaics: Installing Permanent Dipoles in PCBM Analogues. J Phys Chem A 2015; 120:4664-71. [PMID: 26478954 DOI: 10.1021/acs.jpca.5b09279] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A multidisciplinary approach involving organic synthesis and theoretical chemistry was applied to investigate a promising strategy to improve charge separation in organic photovoltaics: installing permanent dipoles in fullerene derivatives. First, a PCBM analogue with a permanent dipole in the side chain (PCBDN) and its reference analogue without a permanent dipole (PCBBz) were successfully synthesized and characterized. Second, a multiscale modeling approach was applied to investigate if a PCBDN environment around a central donor-acceptor complex indeed facilitates charge separation. Alignment of the embedding dipoles in response to charges present on the central donor-acceptor complex enhances charge separation. The good correspondence between experimentally and theoretically determined electronic and optical properties of PCBDN, PCBBz, and PCBM indicates that the theoretical analysis of the embedding effects of these molecules gives a reliable expectation for their influence on the charge separation process at a microscopic scale in a real device. This work suggests the following strategies to improve charge separation in organic photovoltaics: installing permanent dipoles in PCBM analogues and tuning the concentration of these molecules in an organic donor/acceptor blend.
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Affiliation(s)
- Hilde D de Gier
- Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Fatemeh Jahani
- Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.,Stratingh Institute for Chemistry, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Ria Broer
- Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Jan C Hummelen
- Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.,Stratingh Institute for Chemistry, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Remco W A Havenith
- Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.,Stratingh Institute for Chemistry, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.,Ghent Quantum Chemistry Group, Department of Inorganic and Physical Chemistry, Ghent University , Krijgslaan 281 (S3), B-9000 Gent, Belgium
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215
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Hu Z, Willard AP, Ono RJ, Bielawski CW, Rossky PJ, Vanden Bout DA. An insight into non-emissive excited states in conjugated polymers. Nat Commun 2015; 6:8246. [PMID: 26391514 PMCID: PMC4595598 DOI: 10.1038/ncomms9246] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2014] [Accepted: 08/03/2015] [Indexed: 11/25/2022] Open
Abstract
Conjugated polymers in the solid state usually exhibit low fluorescence quantum yields, which limit their applications in many areas such as light-emitting diodes. Despite considerable research efforts, the underlying mechanism still remains controversial and elusive. Here, the nature and properties of excited states in the archetypal polythiophene are investigated via aggregates suspended in solvents with different dielectric constants (ɛ). In relatively polar solvents (ɛ>∼ 3), the aggregates exhibit a low fluorescence quantum yield (QY) of 2–5%, similar to bulk films, however, in relatively nonpolar solvents (ɛ<∼ 3) they demonstrate much higher fluorescence QY up to 20–30%. A series of mixed quantum-classical atomistic simulations illustrate that dielectric induced stabilization of nonradiative charge-transfer (CT) type states can lead to similar drastic reduction in fluorescence QY as seen experimentally. Fluorescence lifetime measurement reveals that the CT-type states exist as a competitive channel of the formation of emissive exciton-type states. Conjugated polymers in thin films exhibit low fluorescence quantum yields, but the mechanism is still unclear. Here, Hu et al. show the trade-off between charge transfer and emissive exciton states, whilst the former can be suppressed via dielectric-induced stabilization for large fluorescence quantum yields.
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Affiliation(s)
- Zhongjian Hu
- Center for Nano- and Molecular Science and Technology, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - Adam P Willard
- Center for Nano- and Molecular Science and Technology, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - Robert J Ono
- Center for Nano- and Molecular Science and Technology, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - Christopher W Bielawski
- Center for Nano- and Molecular Science and Technology, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - Peter J Rossky
- Center for Nano- and Molecular Science and Technology, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - David A Vanden Bout
- Center for Nano- and Molecular Science and Technology, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
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216
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Zhong Y, Trinh MT, Chen R, Purdum GE, Khlyabich PP, Sezen M, Oh S, Zhu H, Fowler B, Zhang B, Wang W, Nam CY, Sfeir MY, Black CT, Steigerwald ML, Loo YL, Ng F, Zhu XY, Nuckolls C. Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells. Nat Commun 2015; 6:8242. [PMID: 26382113 PMCID: PMC4595599 DOI: 10.1038/ncomms9242] [Citation(s) in RCA: 493] [Impact Index Per Article: 54.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 07/29/2015] [Indexed: 12/25/2022] Open
Abstract
Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells.
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Affiliation(s)
- Yu Zhong
- Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA
| | - M Tuan Trinh
- Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA
| | - Rongsheng Chen
- Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA.,School of Chemical Engineering and Technology, Wuhan University of Science and Technology, Wuhan 430081, China
| | - Geoffrey E Purdum
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Petr P Khlyabich
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Melda Sezen
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Seokjoon Oh
- Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA
| | - Haiming Zhu
- Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA
| | - Brandon Fowler
- Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA
| | - Boyuan Zhang
- Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA
| | - Wei Wang
- Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA
| | - Chang-Yong Nam
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, New York 11973, USA
| | - Matthew Y Sfeir
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, New York 11973, USA
| | - Charles T Black
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, New York 11973, USA
| | - Michael L Steigerwald
- Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA
| | - Yueh-Lin Loo
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Fay Ng
- Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA
| | - X-Y Zhu
- Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA
| | - Colin Nuckolls
- Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA
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217
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Lee Y, Gomez ED. Challenges and Opportunities in the Development of Conjugated Block Copolymers for Photovoltaics. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b00112] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Youngmin Lee
- Department of Chemical Engineering and ‡Materials Research
Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Enrique D. Gomez
- Department of Chemical Engineering and ‡Materials Research
Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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218
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Li Y, Feng Y, Sun M. Photoinduced Charge Transport in a BHJ Solar Cell Controlled by an External Electric Field. Sci Rep 2015; 5:13970. [PMID: 26353997 PMCID: PMC4564800 DOI: 10.1038/srep13970] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 08/12/2015] [Indexed: 11/18/2022] Open
Abstract
This study investigated theoretical photoinduced charge transport in a bulk heterojunction (BHJ) solar cell controlled by an external electric field. Our method for visualizing charge difference density identified the excited state properties of photoinduced charge transfer, and the charge transfer excited states were distinguished from local excited states during electronic transitions. Furthermore, the calculated rates for the charge transfer revealed that the charge transfer was strongly influenced by the external electric field. The external electric field accelerated the rate of charge transfer by up to one order when charge recombination was significantly restrained. Our research demonstrated that photoinduced charge transport controlled by an external electric field in a BHJ solar cell is efficient, and the exciton dissociation is not the limiting factor in organic solar cells.Our research should aid in the rational design of a novel conjugated system of organic solar cells.
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Affiliation(s)
- Yongqing Li
- Department of Physics, Liaoning University, Shenyang 110036, P. R. China
- State Key Lab of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Yanting Feng
- Department of Physics, Liaoning University, Shenyang 110036, P. R. China
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, P. O. Box 603-146, Beijing, 100190, P. R. China
| | - Mengtao Sun
- Department of Physics, Liaoning University, Shenyang 110036, P. R. China
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, P. O. Box 603-146, Beijing, 100190, P. R. China
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219
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Fischer SA, Cramer CJ, Govind N. Excited State Absorption from Real-Time Time-Dependent Density Functional Theory. J Chem Theory Comput 2015; 11:4294-303. [DOI: 10.1021/acs.jctc.5b00473] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Sean A. Fischer
- Environmental
Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Christopher J. Cramer
- Department
of Chemistry, Supercomputing Institute and Chemical Theory Center, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Niranjan Govind
- Environmental
Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
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220
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Chen L, Shenai P, Zheng F, Somoza A, Zhao Y. Optimal Energy Transfer in Light-Harvesting Systems. Molecules 2015; 20:15224-72. [PMID: 26307957 PMCID: PMC6332264 DOI: 10.3390/molecules200815224] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 08/03/2015] [Accepted: 08/14/2015] [Indexed: 01/25/2023] Open
Abstract
Photosynthesis is one of the most essential biological processes in which specialized pigment-protein complexes absorb solar photons, and with a remarkably high efficiency, guide the photo-induced excitation energy toward the reaction center to subsequently trigger its conversion to chemical energy. In this work, we review the principles of optimal energy transfer in various natural and artificial light harvesting systems. We begin by presenting the guiding principles for optimizing the energy transfer efficiency in systems connected to dissipative environments, with particular attention paid to the potential role of quantum coherence in light harvesting systems. We will comment briefly on photo-protective mechanisms in natural systems that ensure optimal functionality under varying ambient conditions. For completeness, we will also present an overview of the charge separation and electron transfer pathways in reaction centers. Finally, recent theoretical and experimental progress on excitation energy transfer, charge separation, and charge transport in artificial light harvesting systems is delineated, with organic solar cells taken as prime examples.
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Affiliation(s)
- Lipeng Chen
- Division of Materials Science, Nanyang Technological University, 50 Nanyang Avenue,Singapore 639798, Singapore.
| | - Prathamesh Shenai
- Division of Materials Science, Nanyang Technological University, 50 Nanyang Avenue,Singapore 639798, Singapore.
| | - Fulu Zheng
- Division of Materials Science, Nanyang Technological University, 50 Nanyang Avenue,Singapore 639798, Singapore.
| | - Alejandro Somoza
- Division of Materials Science, Nanyang Technological University, 50 Nanyang Avenue,Singapore 639798, Singapore.
| | - Yang Zhao
- Division of Materials Science, Nanyang Technological University, 50 Nanyang Avenue,Singapore 639798, Singapore.
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221
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Min SK, Agostini F, Gross EKU. Coupled-Trajectory Quantum-Classical Approach to Electronic Decoherence in Nonadiabatic Processes. PHYSICAL REVIEW LETTERS 2015; 115:073001. [PMID: 26317716 DOI: 10.1103/physrevlett.115.073001] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Indexed: 06/04/2023]
Abstract
We present a novel quantum-classical approach to nonadiabatic dynamics, deduced from the coupled electronic and nuclear equations in the framework of the exact factorization of the electron-nuclear wave function. The method is based on the quasiclassical interpretation of the nuclear wave function, whose phase is related to the classical momentum and whose density is represented in terms of classical trajectories. In this approximation, electronic decoherence is naturally induced as an effect of the coupling to the nuclei and correctly reproduces the expected quantum behavior. Moreover, the splitting of the nuclear wave packet is captured as a consequence of the correct approximation of the time-dependent potential of the theory. This new approach offers a clear improvement over Ehrenfest-like dynamics. The theoretical derivation presented in this Letter is supported by numerical results that are compared to quantum mechanical calculations.
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Affiliation(s)
- Seung Kyu Min
- Max-Planck Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
- Department of Chemistry, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea
| | - Federica Agostini
- Max-Planck Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
| | - E K U Gross
- Max-Planck Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
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222
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Lee MH, Geva E, Dunietz BD. The Effect of Interfacial Geometry on Charge-Transfer States in the Phthalocyanine/Fullerene Organic Photovoltaic System. J Phys Chem A 2015; 120:2970-5. [DOI: 10.1021/acs.jpca.5b06196] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Myeong H. Lee
- Department
of Chemistry and Centre for Scientific Computing, University of Warwick, Coventry CV4 7AL, U.K
| | - Eitan Geva
- Department
of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Barry D. Dunietz
- Department
of Chemistry, Kent State University, Kent, Ohio 44242, United States
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223
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Agostini F, Abedi A, Suzuki Y, Min SK, Maitra NT, Gross EKU. The exact forces on classical nuclei in non-adiabatic charge transfer. J Chem Phys 2015; 142:084303. [PMID: 25725727 DOI: 10.1063/1.4908133] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The decomposition of electronic and nuclear motion presented in Abedi et al. [Phys. Rev. Lett. 105, 123002 (2010)] yields a time-dependent potential that drives the nuclear motion and fully accounts for the coupling to the electronic subsystem. Here, we show that propagation of an ensemble of independent classical nuclear trajectories on this exact potential yields dynamics that are essentially indistinguishable from the exact quantum dynamics for a model non-adiabatic charge transfer problem. We point out the importance of step and bump features in the exact potential that are critical in obtaining the correct splitting of the quasiclassical nuclear wave packet in space after it passes through an avoided crossing between two Born-Oppenheimer surfaces and analyze their structure. Finally, an analysis of the exact potentials in the context of trajectory surface hopping is presented, including preliminary investigations of velocity-adjustment and the force-induced decoherence effect.
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Affiliation(s)
- Federica Agostini
- Max-Planck-Institut of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany
| | - Ali Abedi
- Max-Planck-Institut of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany
| | - Yasumitsu Suzuki
- Max-Planck-Institut of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany
| | - Seung Kyu Min
- Max-Planck-Institut of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany
| | - Neepa T Maitra
- Department of Physics and Astronomy, Hunter College and the Graduate Center of the City University of New York, 695 Park Avenue, New York, New York 10065, USA
| | - E K U Gross
- Max-Planck-Institut of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany
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224
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Ouyang W, Dou W, Subotnik JE. Surface hopping with a manifold of electronic states. I. Incorporating surface-leaking to capture lifetimes. J Chem Phys 2015; 142:084109. [PMID: 25725714 DOI: 10.1063/1.4908032] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate the incorporation of the surface-leaking (SL) algorithm into Tully's fewest-switches surface hopping (FSSH) algorithm to simulate some electronic relaxation induced by an electronic bath in conjunction with some electronic transitions between discrete states. The resulting SL-FSSH algorithm is benchmarked against exact quantum scattering calculations for three one-dimensional model problems. The results show excellent agreement between SL-FSSH and exact quantum dynamics in the wide band limit, suggesting the potential for a SL-FSSH algorithm. Discrepancies and failures are investigated in detail to understand the factors that will limit the reliability of SL-FSSH, especially the wide band approximation. Considering the easiness of implementation and the low computational cost, we expect this method to be useful in studying processes involving both a continuum of electronic states (where electronic dynamics are probabilistic) and processes involving only a few electronic states (where non-adiabatic processes cannot ignore short-time coherence).
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Affiliation(s)
- Wenjun Ouyang
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Wenjie Dou
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Joseph E Subotnik
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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225
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Lane PA, Cunningham PD, Melinger JS, Esenturk O, Heilweil EJ. Hot photocarrier dynamics in organic solar cells. Nat Commun 2015; 6:7558. [DOI: 10.1038/ncomms8558] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Accepted: 05/19/2015] [Indexed: 11/09/2022] Open
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226
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Abstract
Recent experiments aimed at probing the dynamics of excitons have revealed that semiconducting films composed of disordered molecular subunits, unlike expectations for their perfectly ordered counterparts, can exhibit a time-dependent diffusivity in which the effective early time diffusion constant is larger than that of the steady state. This observation has led to speculation about what role, if any, microscopic disorder may play in enhancing exciton transport properties. In this article, we present the results of a model study aimed at addressing this point. Specifically, we introduce a general model, based upon Förster theory, for incoherent exciton diffusion in a material composed of independent molecular subunits with static energetic disorder. Energetic disorder leads to heterogeneity in molecule-to-molecule transition rates, which we demonstrate has two important consequences related to exciton transport. First, the distribution of local site-specific hopping rates is broadened in a manner that results in a decrease in average exciton diffusivity relative to that in a perfectly ordered film. Second, since excitons prefer to make transitions that are downhill in energy, the steady state distribution of exciton energies is biased toward low-energy molecular subunits, those that exhibit reduced diffusivity relative to a perfectly ordered film. These effects combine to reduce the net diffusivity in a manner that is time dependent and grows more pronounced as disorder is increased. Notably, however, we demonstrate that the presence of energetic disorder can give rise to a population of molecular subunits with exciton transfer rates exceeding those of subunits in an energetically uniform material. Such enhancements may play an important role in processes that are sensitive to molecular-scale fluctuations in exciton density field.
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Affiliation(s)
- Elizabeth M Y Lee
- †Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - William A Tisdale
- †Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Adam P Willard
- ‡Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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227
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Wang J, Huang J, Du L, Lan Z. Photoinduced Ultrafast Intramolecular Excited-State Energy Transfer in the Silylene-Bridged Biphenyl and Stilbene (SBS) System: A Nonadiabatic Dynamics Point of View. J Phys Chem A 2015; 119:6937-48. [DOI: 10.1021/acs.jpca.5b00354] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jun Wang
- Key
Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy
and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 Shandong, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Jing Huang
- Key
Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy
and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 Shandong, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Likai Du
- Key
Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy
and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 Shandong, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Zhenggang Lan
- Key
Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy
and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 Shandong, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
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228
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Monahan NR, Williams KW, Kumar B, Nuckolls C, Zhu XY. Direct Observation of Entropy-Driven Electron-Hole Pair Separation at an Organic Semiconductor Interface. PHYSICAL REVIEW LETTERS 2015. [PMID: 26196998 DOI: 10.1103/physrevlett.114.247003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
How an electron-hole pair escapes the Coulomb potential at a donor-acceptor interface has been a key issue in organic photovoltaic research. Recent evidence suggests that long-distance charge separation can occur on ultrafast time scales, yet the underlying mechanism remains unclear. Here we use charge transfer excitons (CTEs) across an organic semiconductor-vacuum interface as a model and show that nascent hot CTEs can spontaneously climb up the Coulomb potential within 100 fs. This process is driven by entropic gain due to the rapid rise in density of states with increasing electron-hole separation. In contrast, the lowest CTE cannot delocalize, but undergoes self-trapping and recombination.
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Affiliation(s)
- Nicholas R Monahan
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, USA
| | - Kristopher W Williams
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, USA
| | - Bharat Kumar
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, USA
| | - Colin Nuckolls
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, USA
| | - X-Y Zhu
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, USA
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229
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Devižis A, De Jonghe-Risse J, Hany R, Nüesch F, Jenatsch S, Gulbinas V, Moser JE. Dissociation of Charge Transfer States and Carrier Separation in Bilayer Organic Solar Cells: A Time-Resolved Electroabsorption Spectroscopy Study. J Am Chem Soc 2015; 137:8192-8. [PMID: 26037526 DOI: 10.1021/jacs.5b03682] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ultrafast optical probing of the electric field by means of Stark effect in planar heterojunction cyanine dye/fullerene organic solar cells enables one to directly monitor the dynamics of free electron formation during the dissociation of interfacial charge transfer (CT) states. Motions of electrons and holes is scrutinized separately by selectively probing the Stark shift dynamics at selected wavelengths. It is shown that only charge pairs with an effective electron-hole separation distance of less than 4 nm are created during the dissociation of Frenkel excitons. Dissociation of the coulombically bound charge pairs is identified as the major rate-limiting step for charge carriers' generation. Interfacial CT states split into free charges on the time-scale of tens to hundreds of picoseconds, mainly by electron escape from the Coulomb potential over a barrier that is lowered by the electric field. The motion of holes in the small molecule donor material during the charge separation time is found to be insignificant.
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Affiliation(s)
- Andrius Devižis
- ∥Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania
| | | | - Roland Hany
- §Laboratory for Functional Polymers, EMPA, Swiss Federal Laboratories for Materials Science and Technology, CH-8600, Dübendorf, Switzerland
| | - Frank Nüesch
- §Laboratory for Functional Polymers, EMPA, Swiss Federal Laboratories for Materials Science and Technology, CH-8600, Dübendorf, Switzerland
| | - Sandra Jenatsch
- §Laboratory for Functional Polymers, EMPA, Swiss Federal Laboratories for Materials Science and Technology, CH-8600, Dübendorf, Switzerland
| | - Vidmantas Gulbinas
- ∥Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania
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230
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Zhu X, Monahan NR, Gong Z, Zhu H, Williams KW, Nelson CA. Charge Transfer Excitons at van der Waals Interfaces. J Am Chem Soc 2015; 137:8313-20. [DOI: 10.1021/jacs.5b03141] [Citation(s) in RCA: 216] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Nicholas R. Monahan
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Zizhou Gong
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Haiming Zhu
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | | | - Cory A. Nelson
- Department of Chemistry, Columbia University, New York, New York 10027, United States
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231
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Izawa S, Nakano K, Suzuki K, Hashimoto K, Tajima K. Dominant effects of first monolayer energetics at donor/acceptor interfaces on organic photovoltaics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:3025-3031. [PMID: 25856403 DOI: 10.1002/adma.201500840] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 03/10/2015] [Indexed: 06/04/2023]
Abstract
Energy levels of the first monolayer are manipulated at donor/acceptor interfaces in planar heterojunction organic photovoltaics by using molecular self-organization. A "cascade" energy landscape allows thermal-activation-free charge generation by photoirradiation, destabilizes the energy of the interfacial charge-transfer state, and suppresses bimolecular charge recombination, resulting in a higher open-circuit voltage and fill factor.
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Affiliation(s)
- Seiichiro Izawa
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
- Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Kyohei Nakano
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Kaori Suzuki
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Kazuhito Hashimoto
- Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Keisuke Tajima
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
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232
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Ke Y, Liu Y, Zhao Y. Visualization of Hot Exciton Energy Relaxation from Coherent to Diffusive Regimes in Conjugated Polymers: A Theoretical Analysis. J Phys Chem Lett 2015; 6:1741-1747. [PMID: 26263343 DOI: 10.1021/acs.jpclett.5b00490] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The unified coherent-to-diffusive energy relaxation of hot exciton in organic aggregates or polymers, which still remains largely unclear and is also a great challenge theoretically, is investigated from a time-dependent wavepacket diffusive approach. The results demonstrate that in the multiple time scale energy relaxation dynamics, the fast relaxation time essentially corresponds to the dephasing time of excitonic coherence motion, whereas the slow time is related to a hopping migration, and a suggested kinetic model successfully connects these two processes. The dependencies of those times on the initial energy and delocalization of exciton wavepacket as well as exciton-phonon interactions are further analyzed. The proposed method together with quantum chemistry calculations has explained an experimental observation of hot exciton energy relaxation in the low-bandgap copolymer PBDTTPD.
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Affiliation(s)
- Yaling Ke
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, Fujian Provincial Key Lab of Theoretical and Computational Chemistry, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China
| | - Yuxiu Liu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, Fujian Provincial Key Lab of Theoretical and Computational Chemistry, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China
| | - Yi Zhao
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, Fujian Provincial Key Lab of Theoretical and Computational Chemistry, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China
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233
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Huix-Rotllant M, Tamura H, Burghardt I. Concurrent Effects of Delocalization and Internal Conversion Tune Charge Separation at Regioregular Polythiophene-Fullerene Heterojunctions. J Phys Chem Lett 2015; 6:1702-1708. [PMID: 26263337 DOI: 10.1021/acs.jpclett.5b00336] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Quantum-dynamical simulations are used to investigate the interplay of exciton delocalization and vibronically induced internal conversion processes in the elementary charge separation steps at regioregular donor-acceptor heterojunctions. Ultrafast internal conversion leads to efficient deexcitation within the excitonic and charge transfer manifolds, thus modifying the charge separation dynamics. We address a model donor-acceptor junction representative of regioregular P3HT-PCBM, using high-dimensional quantum dynamics simulations by multiconfigurational methods. While partial trapping into an interfacial charge separated state occurs, long-range charge-separated states are accessed as previously demonstrated in the work of Tamura and Burghardt [J. Am. Chem. Soc. 2013, 135, 16364]. For an H-aggregate type, stacked donor species, the initial bright state undergoes ultrafast internal conversion within the excitonic manifold, creating multiple charge transfer pathways before reaching the lowest-energy dark exciton, which is uncoupled from the charge transfer manifold. This process profoundly affects the charge separation mechanism and efficiency. For small energetic offsets between the interfacial excitonic and charge transfer states, a delocalized initial bright state proves less prone to electron-hole capture by the interfacial trap than a localized, vibronic wavepacket close to the interface. For both delocalized and localized initial states, a comparable yield of free carriers is obtained, which is found to be optimal for energetic offsets of the order of the Coulomb barrier to charge separation. Interfacial trapping is significantly reduced as the barrier height decreases with fullerene aggregation. Despite the high-dimensional nature of the system, charge separation is an ultrafast coherent quantum process exhibiting oscillatory features as observed in recent experiments.
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Affiliation(s)
- Miquel Huix-Rotllant
- †Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany
| | - Hiroyuki Tamura
- ‡WPI-Advanced Institute for Material Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Irene Burghardt
- †Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany
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234
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Manna AK, Balamurugan D, Cheung MS, Dunietz BD. Unraveling the Mechanism of Photoinduced Charge Transfer in Carotenoid-Porphyrin-C60 Molecular Triad. J Phys Chem Lett 2015; 6:1231-1237. [PMID: 26262978 DOI: 10.1021/acs.jpclett.5b00074] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Photoinduced charge transfer (CT) plays a central role in biologically significant systems and in applications that harvest solar energy. We investigate the relationship of CT kinetics and conformation in a molecular triad. The triad, consisting of carotenoid, porphyrin, and fullerene is structurally flexible and able to acquire significantly varied conformations under ambient conditions. With an integrated approach of quantum calculations and molecular dynamics simulations, we compute the rate of CT at two distinctive conformations. The linearly extended conformation, in which the donor (carotenoid) and the acceptor (fullerene) are separated by nearly 50 Å, enables charge separation through a sequential CT process. A representative bent conformation that is entropically dominant, however, attenuates the CT, although the donor and the acceptor are spatially closer. Our computed rate of CT at the linear conformation is in good agreement with measured values. Our work provides unique fundamental understanding of the photoinduced CT process in the molecular triad.
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Affiliation(s)
- Arun K Manna
- †Department of Chemistry, Kent State University, 1787 Summit Street, Kent, Ohio 44242, United States
| | - D Balamurugan
- ∥Computation Institute, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637, United States
| | - Margaret S Cheung
- §Center for Theoretical Biological Physics, Rice University, 6500 Main Street, Houston, Texas 77030, United States
| | - Barry D Dunietz
- †Department of Chemistry, Kent State University, 1787 Summit Street, Kent, Ohio 44242, United States
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235
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Di Nuzzo D, Viola D, Fischer FSU, Cerullo G, Ludwigs S, Da Como E. Enhanced Photogeneration of Polaron Pairs in Neat Semicrystalline Donor-Acceptor Copolymer Films via Direct Excitation of Interchain Aggregates. J Phys Chem Lett 2015; 6:1196-1203. [PMID: 26262971 DOI: 10.1021/acs.jpclett.5b00218] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We investigate the photogeneration of polaron pairs (PPs) in neat films of the semicrystalline donor-acceptor semiconducting copolymer PCPDTBT. Carefully selecting the solution-processing procedures, we obtain films with different amounts of crystallinity and interchain aggregation. We compare the photogeneration of PPs between the films by monitoring their photoinduced absorption in ultrafast pump-probe experiments, selectively exciting nonaggregated or aggregated polymer chains. The direct photoexcitation of interchain π-aggregates results in prompt (<100 fs) charge generation. Compared to the case where nonaggregated chains are excited, we find an 8-fold increase in the prompt PP to singlet-exciton ratio. We also show that highly crystalline lamellar nanostructures not containing π-stacked or any light-absorbing aggregates do not improve the efficiency of PP photogeneration. Our results show that light absorption from interchain aggregates is highly beneficial for charge photogeneration in semiconducting polymers and should be taken into account when optimizing film morphologies for photovoltaic devices.
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Affiliation(s)
- Daniele Di Nuzzo
- †Department of Physics, University of Bath, BA2 7AY Bath, United Kingdom
| | - Daniele Viola
- ‡Dipartimento di Fisica, IFN-CNR, Politecnico di Milano, 20133 Milano, Italy
| | - Florian S U Fischer
- §IPOC-Functional Polymers, University of Stuttgart, 70569 Stuttgart, Germany
| | - Giulio Cerullo
- ‡Dipartimento di Fisica, IFN-CNR, Politecnico di Milano, 20133 Milano, Italy
| | - Sabine Ludwigs
- §IPOC-Functional Polymers, University of Stuttgart, 70569 Stuttgart, Germany
| | - Enrico Da Como
- †Department of Physics, University of Bath, BA2 7AY Bath, United Kingdom
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236
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Poelking C, Tietze M, Elschner C, Olthof S, Hertel D, Baumeier B, Würthner F, Meerholz K, Leo K, Andrienko D. Impact of mesoscale order on open-circuit voltage in organic solar cells. NATURE MATERIALS 2015; 14:434-439. [PMID: 25532071 DOI: 10.1038/nmat4167] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 11/05/2014] [Indexed: 06/04/2023]
Abstract
Structural order in organic solar cells is paramount: it reduces energetic disorder, boosts charge and exciton mobilities, and assists exciton splitting. Owing to spatial localization of electronic states, microscopic descriptions of photovoltaic processes tend to overlook the influence of structural features at the mesoscale. Long-range electrostatic interactions nevertheless probe this ordering, making local properties depend on the mesoscopic order. Using a technique developed to address spatially aperiodic excitations in thin films and in bulk, we show how inclusion of mesoscale order resolves the controversy between experimental and theoretical results for the energy-level profile and alignment in a variety of photovoltaic systems, with direct experimental validation. Optimal use of long-range ordering also rationalizes the acceptor-donor-acceptor paradigm for molecular design of donor dyes. We predict open-circuit voltages of planar heterojunction solar cells in excellent agreement with experimental data, based only on crystal structures and interfacial orientation.
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Affiliation(s)
- Carl Poelking
- 1] Max Planck Institute for Polymer Research, Ackermannweg 10 55128 Mainz, Germany [2] Heidelberg Graduate School of Fundamental Physics, INF 226 69120 Heidelberg, Germany
| | - Max Tietze
- Institut für Angewandte Photophysik, George-Bähr-Straße 10 01062 Dresden, Germany
| | - Chris Elschner
- Institut für Angewandte Photophysik, George-Bähr-Straße 10 01062 Dresden, Germany
| | - Selina Olthof
- Physikalische Chemie, Universität zu Köln, Luxemburger Straße 116 50939 Köln, Germany
| | - Dirk Hertel
- Physikalische Chemie, Universität zu Köln, Luxemburger Straße 116 50939 Köln, Germany
| | - Björn Baumeier
- Max Planck Institute for Polymer Research, Ackermannweg 10 55128 Mainz, Germany
| | - Frank Würthner
- Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Klaus Meerholz
- Physikalische Chemie, Universität zu Köln, Luxemburger Straße 116 50939 Köln, Germany
| | - Karl Leo
- Institut für Angewandte Photophysik, George-Bähr-Straße 10 01062 Dresden, Germany
| | - Denis Andrienko
- Max Planck Institute for Polymer Research, Ackermannweg 10 55128 Mainz, Germany
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237
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Zhugayevych A, Tretiak S. Theoretical Description of Structural and Electronic Properties of Organic Photovoltaic Materials. Annu Rev Phys Chem 2015; 66:305-30. [DOI: 10.1146/annurev-physchem-040214-121440] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Andriy Zhugayevych
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545;
- Skolkovo Institute of Science and Technology, Moscow, Russia 143025
| | - Sergei Tretiak
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545;
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238
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Gao F, Tress W, Wang J, Inganäs O. Temperature dependence of charge carrier generation in organic photovoltaics. PHYSICAL REVIEW LETTERS 2015; 114:128701. [PMID: 25860774 DOI: 10.1103/physrevlett.114.128701] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Indexed: 06/04/2023]
Abstract
The charge generation mechanism in organic photovoltaics is a fundamental yet heavily debated issue. All the generated charges recombine at the open-circuit voltage (V_{OC}), so that investigation of recombined charges at V_{OC} provides a unique approach to understanding charge generation. At low temperatures, we observe a decrease of V_{OC}, which is attributed to reduced charge separation. Comparison between benchmark polymer:fullerene and polymer:polymer blends highlights the critical role of charge delocalization in charge separation and emphasizes the importance of entropy in charge generation.
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Affiliation(s)
- Feng Gao
- Biomolecular and Organic Electronics, IFM, Linköping University, Linköping 58183, Sweden
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Wolfgang Tress
- Biomolecular and Organic Electronics, IFM, Linköping University, Linköping 58183, Sweden
| | - Jianpu Wang
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), National Synergistic Innovation Centre for Advanced Materials (SICAM), Nanjing Tech University, 30 South Puzhu Road, Nanjing 211816, China
| | - Olle Inganäs
- Biomolecular and Organic Electronics, IFM, Linköping University, Linköping 58183, Sweden
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239
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Zhong C, Choi H, Kim JY, Woo HY, Nguyen TL, Huang F, Cao Y, Heeger AJ. Ultrafast charge transfer in operating bulk heterojunction solar cells. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:2036-2041. [PMID: 25677734 DOI: 10.1002/adma.201405284] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 12/26/2014] [Indexed: 06/04/2023]
Abstract
The ultrafast charge generation process in organic solar cell devices is investigated by transient reflection spectroscopy on five state-of-the-art bulk heterojunction systems. The charge generation process in operating devices is found to be a combination of an ultrafast generation mechanism over several hundred femto-seconds and a slow process from pico-seconds to nanoseconds, limited by exciton diffusion dynamics. In addition, the lack of electric field dependence in the charge dynamics rules out geminate recombination as an important loss mechanism.
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Affiliation(s)
- Chengmei Zhong
- Center for Polymers and Organic Solids, University of California, Santa Barbara, CA, 93106-5090, USA; State Key Laboratory of Luminescent Materials and Devices, Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, PR China
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240
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Jeong S, Cho C, Kang H, Kim KH, Yuk Y, Park JY, Kim BJ, Lee JY. Nanoimprinting-induced nanomorphological transition in polymer solar cells: enhanced electrical and optical performance. ACS NANO 2015; 9:2773-2782. [PMID: 25688838 DOI: 10.1021/nn506678a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We have investigated the effects of a directly nanopatterned active layer on the electrical and optical properties of inverted polymer solar cells (i-PSCs). The capillary force in confined molds plays a critical role in polymer crystallization and phase separation of the film. The nanoimprinting process induced improved crystallization and multidimensional chain alignment of polymers for more effective charge transfer and a fine phase-separation between polymers and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) to favor exciton dissociation and increase the generation rate of charge transfer excitons. Consequently, the power conversion efficiency with a periodic nanostructure was enhanced from 7.40% to 8.50% and 7.17% to 9.15% in PTB7 and PTB7-Th based i-PSCs, respectively.
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Affiliation(s)
- Seonju Jeong
- †Graduate School of Energy, Environment, Water, and Sustainability (EEWS), ‡Graphene Research Center, §Department of Chemical and Biomolecular Engineering, and ∥Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Korea Advanced Institute Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
| | - Changsoon Cho
- †Graduate School of Energy, Environment, Water, and Sustainability (EEWS), ‡Graphene Research Center, §Department of Chemical and Biomolecular Engineering, and ∥Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Korea Advanced Institute Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
| | - Hyunbum Kang
- †Graduate School of Energy, Environment, Water, and Sustainability (EEWS), ‡Graphene Research Center, §Department of Chemical and Biomolecular Engineering, and ∥Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Korea Advanced Institute Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
| | - Ki-Hyun Kim
- †Graduate School of Energy, Environment, Water, and Sustainability (EEWS), ‡Graphene Research Center, §Department of Chemical and Biomolecular Engineering, and ∥Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Korea Advanced Institute Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
| | - Youngji Yuk
- †Graduate School of Energy, Environment, Water, and Sustainability (EEWS), ‡Graphene Research Center, §Department of Chemical and Biomolecular Engineering, and ∥Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Korea Advanced Institute Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
| | - Jeong Young Park
- †Graduate School of Energy, Environment, Water, and Sustainability (EEWS), ‡Graphene Research Center, §Department of Chemical and Biomolecular Engineering, and ∥Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Korea Advanced Institute Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
| | - Bumjoon J Kim
- †Graduate School of Energy, Environment, Water, and Sustainability (EEWS), ‡Graphene Research Center, §Department of Chemical and Biomolecular Engineering, and ∥Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Korea Advanced Institute Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
| | - Jung-Yong Lee
- †Graduate School of Energy, Environment, Water, and Sustainability (EEWS), ‡Graphene Research Center, §Department of Chemical and Biomolecular Engineering, and ∥Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Korea Advanced Institute Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
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241
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Fujii M, Yamashita K. Semiclassical quantization of nonadiabatic systems with hopping periodic orbits. J Chem Phys 2015; 142:074104. [PMID: 25701999 DOI: 10.1063/1.4907910] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a semiclassical quantization condition, i.e., quantum-classical correspondence, for steady states of nonadiabatic systems consisting of fast and slow degrees of freedom (DOFs) by extending Gutzwiller's trace formula to a nonadiabatic form. The quantum-classical correspondence indicates that a set of primitive hopping periodic orbits, which are invariant under time evolution in the phase space of the slow DOF, should be quantized. The semiclassical quantization is then applied to a simple nonadiabatic model and accurately reproduces exact quantum energy levels. In addition to the semiclassical quantization condition, we also discuss chaotic dynamics involved in the classical limit of nonadiabatic dynamics.
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Affiliation(s)
- Mikiya Fujii
- Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - Koichi Yamashita
- Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
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242
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Scarongella M, De Jonghe-Risse J, Buchaca-Domingo E, Causa' M, Fei Z, Heeney M, Moser JE, Stingelin N, Banerji N. A close look at charge generation in polymer:fullerene blends with microstructure control. J Am Chem Soc 2015; 137:2908-18. [PMID: 25650696 DOI: 10.1021/ja510032x] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We reveal some of the key mechanisms during charge generation in polymer:fullerene blends exploiting our well-defined understanding of the microstructures obtained in pBTTT:PCBM systems via processing with fatty acid methyl ester additives. Based on ultrafast transient absorption, electro-absorption, and fluorescence up-conversion spectroscopy, we find that exciton diffusion through relatively phase-pure polymer or fullerene domains limits the rate of electron and hole transfer, while prompt charge separation occurs in regions where the polymer and fullerene are molecularly intermixed (such as the co-crystal phase where fullerenes intercalate between polymer chains in pBTTT:PCBM). We moreover confirm the importance of neat domains, which are essential to prevent geminate recombination of bound electron-hole pairs. Most interestingly, using an electro-absorption (Stark effect) signature, we directly visualize the migration of holes from intermixed to neat regions, which occurs on the subpicosecond time scale. This ultrafast transport is likely sustained by high local mobility (possibly along chains extending from the co-crystal phase to neat regions) and by an energy cascade driving the holes toward the neat domains.
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Affiliation(s)
- Mariateresa Scarongella
- Institute of Chemical Sciences & Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL) , SB ISIC GR-MO, Station 6, CH-1015 Lausanne, Switzerland
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243
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Manna AK, Lee MH, McMahon KL, Dunietz BD. Calculating High Energy Charge Transfer States Using Optimally Tuned Range-Separated Hybrid Functionals. J Chem Theory Comput 2015; 11:1110-7. [DOI: 10.1021/ct501018n] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Arun K. Manna
- Department
of Chemistry, Kent State University, Kent, Ohio 44242, United States
| | - Myeong H. Lee
- Department
of Chemistry, Kent State University, Kent, Ohio 44242, United States
| | - Kayla L. McMahon
- Department
of Chemistry, Kent State University, Kent, Ohio 44242, United States
| | - Barry D. Dunietz
- Department
of Chemistry, Kent State University, Kent, Ohio 44242, United States
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244
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Wilcox DE, Lee MH, Sykes ME, Niedringhaus A, Geva E, Dunietz BD, Shtein M, Ogilvie JP. Ultrafast Charge-Transfer Dynamics at the Boron Subphthalocyanine Chloride/C60 Heterojunction: Comparison between Experiment and Theory. J Phys Chem Lett 2015; 6:569-575. [PMID: 26261981 DOI: 10.1021/jz502278k] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Photoinduced charge-transfer (CT) processes play a key role in many systems, particularly those relevant to organic photovoltaics and photosynthesis. Advancing the understanding of CT processes calls for comparing their rates measured via state-of-the-art time-resolved interface-specific spectroscopic techniques with theoretical predictions based on first-principles molecular models. We measure charge-transfer rates across a boron subphthalocyanine chloride (SubPc)/C60 heterojunction, commonly used in organic photovoltaics, via heterodyne-detected time-resolved second-harmonic generation. We compare these results to theoretical predictions based on a Fermi's golden rule approach, with input parameters obtained using first-principles calculations for two different equilibrium geometries of a molecular donor-acceptor in a dielectric continuum model. The calculated rates (∼2 ps(-1)) overestimate the measured rates (∼0.1 ps(-1)), which is consistent with the expectation that the calculated rates represent an upper bound over the experimental ones. The comparison provides valuable understanding of how the structure of the electron donor-acceptor interface affects the CT kinetics in organic photovoltaic systems.
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Affiliation(s)
- Daniel E Wilcox
- †Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109, United States
| | - Myeong H Lee
- ∥Department of Chemistry, Kent State University, 214 Williams Hall, Kent, Ohio 44242, United States
| | | | - Andrew Niedringhaus
- †Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109, United States
| | | | - Barry D Dunietz
- ∥Department of Chemistry, Kent State University, 214 Williams Hall, Kent, Ohio 44242, United States
| | | | - Jennifer P Ogilvie
- †Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109, United States
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245
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Chen Y, Cui Y, Zhang S, Hou J. Molecular design toward efficient polymer solar cells processed by green solvents. Polym Chem 2015. [DOI: 10.1039/c5py00431d] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel polymer and a series of new fullerene derivatives were designed and synthesized for green solvent processable photovoltaic applications, which results in a comparable PCE of 4.50% processed by anisole rather than DCB.
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Affiliation(s)
- Yu Chen
- State Key Laboratory of Polymer Physics and Chemistry
- Beijing National Laboratory for Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing
| | - Yong Cui
- State Key Laboratory of Polymer Physics and Chemistry
- Beijing National Laboratory for Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing
| | - Shaoqing Zhang
- State Key Laboratory of Polymer Physics and Chemistry
- Beijing National Laboratory for Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing
| | - Jianhui Hou
- State Key Laboratory of Polymer Physics and Chemistry
- Beijing National Laboratory for Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing
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246
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Dutton GJ, Robey SW. Non-fullerene acceptors: exciton dissociation with PTCDA versus C60. Phys Chem Chem Phys 2015; 17:15953-62. [DOI: 10.1039/c5cp02800k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Extensive development of new polymer and small molecule donors has helped produce a steady increase in the efficiency of organic photovoltaic (OPV) devices.
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Affiliation(s)
| | - Steven W. Robey
- National Institute of Standards and Technology
- Gaithersburg
- USA
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247
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Fazzi D, Barbatti M, Thiel W. Modeling ultrafast exciton deactivation in oligothiophenes via nonadiabatic dynamics. Phys Chem Chem Phys 2015; 17:7787-99. [DOI: 10.1039/c5cp00019j] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Nonadiabatic excited-state dynamics reveal the exciton relaxation processes in oligothiophenes. Ultrafast deactivation and exciton localization are predicted to occur within 200 fs, involving bond stretching, ring puckering, and torsional oscillations.
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Affiliation(s)
- Daniele Fazzi
- Max-Planck-Institut für Kohlenforschung
- D-45470 Mülheim an der Ruhr
- Germany
| | - Mario Barbatti
- Max-Planck-Institut für Kohlenforschung
- D-45470 Mülheim an der Ruhr
- Germany
| | - Walter Thiel
- Max-Planck-Institut für Kohlenforschung
- D-45470 Mülheim an der Ruhr
- Germany
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248
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Bässler H, Köhler A. “Hot or cold”: how do charge transfer states at the donor–acceptor interface of an organic solar cell dissociate? Phys Chem Chem Phys 2015; 17:28451-62. [DOI: 10.1039/c5cp04110d] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This perspective discusses concepts to understand efficient photogeneration of charges in organic semiconductors, with particular emphasis on the role of excess energy.
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Affiliation(s)
- Heinz Bässler
- Bayreuth Institute of Macromolecular Research
- Universität Bayreuth
- 95440 Bayreuth
- Germany
| | - Anna Köhler
- Bayreuth Institute of Macromolecular Research
- Universität Bayreuth
- 95440 Bayreuth
- Germany
- Experimentalphysik II (Organic Semiconductors)
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249
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250
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Shimazaki T, Nakajima T. Theoretical study of exciton dissociation through hot states at donor–acceptor interface in organic photocell. Phys Chem Chem Phys 2015; 17:12538-44. [DOI: 10.1039/c5cp00740b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We theoretically study the dissociation of geminate electron–hole pairs (i.e., excitons) through vibrational hot states at the donor–acceptor interface of organic photocells.
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