1
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Muth D, Anhäuser S, Bischof D, Krüger A, Witte G, Gerhard M. Transport, trapping, triplet fusion: thermally retarded exciton migration in tetracene single crystals. NANOSCALE 2024; 16:13471-13482. [PMID: 38938080 DOI: 10.1039/d4nr01086h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/29/2024]
Abstract
Efficient exciton migration is crucial for optoelectronic organic devices. While the transport of triplet excitons is generally slow compared to singlet excitons, triplet exciton migration in certain molecular semiconductors with endothermic singlet fission appears to be enhanced by a time-delayed regeneration of the more mobile singlet species via triplet fusion. This combined transport mechanism could be exploited for devices, but the interplay between singlet fission and triplet fusion, as well as the role of trap states is not yet well understood. Here, we study the spatiotemporal exciton dynamics in the singlet fission material tetracene by means of time resolved photoluminescence micro-spectroscopy on crystalline samples of different quality. Varying the temperature allows us to modify the dynamic equilibrium between singlet, triplet and trapped excitons. Supported by a kinetic model, we find that thermally activated dissociation of triplet pairs into free triplet excitons can account for an increase of the diffusion length below room temperature. Moreover, we demonstrate that trapping competes efficiently with exciton migration.
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Affiliation(s)
- Dominik Muth
- Department of Physics and Material Sciences Center, Semiconductor Spectroscopy Group, Philipps-Universität Marburg, Renthof 7a, 35032 Marburg, Germany.
| | - Sebastian Anhäuser
- Department of Physics and Material Sciences Center, Molecular Solids Group, Philipps-Universität Marburg, Renthof 7, 35032 Marburg, Germany.
| | - Daniel Bischof
- Department of Physics and Material Sciences Center, Molecular Solids Group, Philipps-Universität Marburg, Renthof 7, 35032 Marburg, Germany.
| | - Anton Krüger
- Department of Physics and Material Sciences Center, Semiconductor Spectroscopy Group, Philipps-Universität Marburg, Renthof 7a, 35032 Marburg, Germany.
| | - Gregor Witte
- Department of Physics and Material Sciences Center, Molecular Solids Group, Philipps-Universität Marburg, Renthof 7, 35032 Marburg, Germany.
| | - Marina Gerhard
- Department of Physics and Material Sciences Center, Semiconductor Spectroscopy Group, Philipps-Universität Marburg, Renthof 7a, 35032 Marburg, Germany.
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2
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Fan B, Zhong W, Gao W, Fu H, Lin FR, Wong RWY, Liu M, Zhu C, Wang C, Yip HL, Liu F, Jen AKY. Understanding the Role of Removable Solid Additives: Selective Interaction Contributes to Vertical Component Distributions. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2302861. [PMID: 37164341 DOI: 10.1002/adma.202302861] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 05/09/2023] [Indexed: 05/12/2023]
Abstract
Sequentially deposited organic solar cells (SD-OSCs) have attracted great attention owing to their ability in achieving a more favorable, vertically phase-separated morphology to avoid the accumulation of counter charges at absorber/transporting layer interfaces. However, the processing of SD-OSCs is still quite challenging in preventing the penetration of small-molecule acceptors into the polymer donor layer via erosion or swelling. Herein, solid additives (SAs) with varied electrostatic potential distributions and steric hinderance are introduced into SD-OSCs to investigate the effect of evaporation dynamics and selective interaction on vertical component distribution. Multiple modelings indicate that the π-π interaction dominates the interactions between aromatic SAs and active layer components. Among them, p-dibromobenzene shows a stronger interaction with the donor while 2-chloronaphthalene (2-CN) interacts more preferably with acceptor. Combining the depth-dependent morphological study aided by multiple X-ray scattering methods, it is concluded that the evaporation of SAs can drive the stronger-interaction component upward to the surface, while having minor impact on the overall molecular packing. Ultimately, the 2-CN-treated devices with reduced acceptor concentration at the bottom surface deliver a high power conversion efficiency of 19.2%, demonstrating the effectiveness of applying selective interactions to improve the vertical morphology of OSCs by using SAs with proper structure.
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Affiliation(s)
- Baobing Fan
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
- Institute of Clean Energy, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
| | - Wenkai Zhong
- Frontiers Science Center for Transformative Molecules, In-Situ Center for Physical Science and Center of Hydrogen Science, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Wei Gao
- Institute of Clean Energy, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
- Department of Material Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
| | - Huiting Fu
- Institute of Clean Energy, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
- Department of Material Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
| | - Francis R Lin
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
- Institute of Clean Energy, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
| | - Reese W-Y Wong
- Department of Material Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
| | - Ming Liu
- Institute of Clean Energy, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
- Department of Material Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
| | - Chenhui Zhu
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Cheng Wang
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Hin-Lap Yip
- Institute of Clean Energy, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
- Department of Material Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
| | - Feng Liu
- Frontiers Science Center for Transformative Molecules, In-Situ Center for Physical Science and Center of Hydrogen Science, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Alex K-Y Jen
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
- Institute of Clean Energy, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
- Department of Material Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong, 999077, P. R. China
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195, USA
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3
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Fu J, Fong PWK, Liu H, Huang CS, Lu X, Lu S, Abdelsamie M, Kodalle T, Sutter-Fella CM, Yang Y, Li G. 19.31% binary organic solar cell and low non-radiative recombination enabled by non-monotonic intermediate state transition. Nat Commun 2023; 14:1760. [PMID: 36997533 PMCID: PMC10063688 DOI: 10.1038/s41467-023-37526-5] [Citation(s) in RCA: 67] [Impact Index Per Article: 67.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Accepted: 03/21/2023] [Indexed: 04/03/2023] Open
Abstract
Non-fullerene acceptors based organic solar cells represent the frontier of the field, owing to both the materials and morphology manipulation innovations. Non-radiative recombination loss suppression and performance boosting are in the center of organic solar cell research. Here, we developed a non-monotonic intermediate state manipulation strategy for state-of-the-art organic solar cells by employing 1,3,5-trichlorobenzene as crystallization regulator, which optimizes the film crystallization process, regulates the self-organization of bulk-heterojunction in a non-monotonic manner, i.e., first enhancing and then relaxing the molecular aggregation. As a result, the excessive aggregation of non-fullerene acceptors is avoided and we have achieved efficient organic solar cells with reduced non-radiative recombination loss. In PM6:BTP-eC9 organic solar cell, our strategy successfully offers a record binary organic solar cell efficiency of 19.31% (18.93% certified) with very low non-radiative recombination loss of 0.190 eV. And lower non-radiative recombination loss of 0.168 eV is further achieved in PM1:BTP-eC9 organic solar cell (19.10% efficiency), giving great promise to future organic solar cell research.
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Affiliation(s)
- Jiehao Fu
- Department of Electronic and Information Engineering, Research Institute for Smart Energy (RISE), Photonic Research Institute (PRI), Guangdong-Hong Kong-Macao Joint Laboratory for Photonic-Thermal-Electrical Energy Materials and Devices, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, 999077, China
- The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen, 518057, China
| | - Patrick W K Fong
- Department of Electronic and Information Engineering, Research Institute for Smart Energy (RISE), Photonic Research Institute (PRI), Guangdong-Hong Kong-Macao Joint Laboratory for Photonic-Thermal-Electrical Energy Materials and Devices, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, 999077, China
- The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen, 518057, China
| | - Heng Liu
- Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong, 999077, China
| | - Chieh-Szu Huang
- Department of Materials Science and Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Xinhui Lu
- Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong, 999077, China
| | - Shirong Lu
- School of Materials Science and Engineering, Taizhou University, Taizhou, 318000, China
| | - Maged Abdelsamie
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Materials Science and Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia
| | - Tim Kodalle
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | | | - Yang Yang
- Department of Materials Science and Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA.
| | - Gang Li
- Department of Electronic and Information Engineering, Research Institute for Smart Energy (RISE), Photonic Research Institute (PRI), Guangdong-Hong Kong-Macao Joint Laboratory for Photonic-Thermal-Electrical Energy Materials and Devices, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, 999077, China.
- The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen, 518057, China.
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4
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Dimitriev OP. Dynamics of Excitons in Conjugated Molecules and Organic Semiconductor Systems. Chem Rev 2022; 122:8487-8593. [PMID: 35298145 DOI: 10.1021/acs.chemrev.1c00648] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The exciton, an excited electron-hole pair bound by Coulomb attraction, plays a key role in photophysics of organic molecules and drives practically important phenomena such as photoinduced mechanical motions of a molecule, photochemical conversions, energy transfer, generation of free charge carriers, etc. Its behavior in extended π-conjugated molecules and disordered organic films is very different and very rich compared with exciton behavior in inorganic semiconductor crystals. Due to the high degree of variability of organic systems themselves, the exciton not only exerts changes on molecules that carry it but undergoes its own changes during all phases of its lifetime, that is, birth, conversion and transport, and decay. The goal of this review is to give a systematic and comprehensive view on exciton behavior in π-conjugated molecules and molecular assemblies at all phases of exciton evolution with emphasis on rates typical for this dynamic picture and various consequences of the above dynamics. To uncover the rich variety of exciton behavior, details of exciton formation, exciton transport, exciton energy conversion, direct and reverse intersystem crossing, and radiative and nonradiative decay are considered in different systems, where these processes lead to or are influenced by static and dynamic disorder, charge distribution symmetry breaking, photoinduced reactions, electron and proton transfer, structural rearrangements, exciton coupling with vibrations and intermediate particles, and exciton dissociation and annihilation as well.
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Affiliation(s)
- Oleg P Dimitriev
- V. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine, pr. Nauki 41, Kyiv 03028, Ukraine
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5
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Raul BAL, Luponosov YN, Yang W, Surin NM, Douhéret O, Min J, Jansen TLC, Ponomarenko SA, Pshenichnikov MS. Excited state dynamics and exciton diffusion in triphenylamine/dicyanovinyl push-pull small molecule for organic optoelectronics. Sci Rep 2020; 10:21198. [PMID: 33273567 PMCID: PMC7713310 DOI: 10.1038/s41598-020-78197-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 11/17/2020] [Indexed: 11/11/2022] Open
Abstract
Triphenylamine-based small push–pull molecules have recently attracted substantial research attention due to their unique optoelectronic properties. Here, we investigate the excited state de-excitation dynamics and exciton diffusion in TPA-T-DCV-Ph-F small molecule, having simple chemical structure with asymmetrical architecture and end-capped with electron-withdrawing p-fluorodicyanovinyl group. The excited state lifetime in diluted solutions (0.04 ns in toluene and 0.4 ns in chloroform) are found to be surprisingly shorter compared to the solid state (3 ns in PMMA matrix). Time-dependent density functional theory indicates that this behavior originates from non-radiative relaxation of the excited state through a conical intersection between the ground and singlet excited state potential energy surfaces. Exciton diffusion length of ~ 16 nm in solution processed films was retrieved by employing time-resolved photoluminescence volume quenching measurements with Monte Carlo simulations. As means of investigating the device performance of TPA-T-DCV-Ph-F, we manufactured solution and vacuum processed bulk heterojunction solar cells that yielded efficiencies of ~ 1.5% and ~ 3.7%, respectively. Our findings demonstrate that the short lifetime in solutions does not hinder per se long exciton diffusion length in films thereby granting applications of TPA-T-DCV-Ph-F and similar push–pull molecules in vacuum and solution processable devices.
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Affiliation(s)
- Benedito A L Raul
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands
| | - Yuriy N Luponosov
- Enikolopov Institute of Synthetic Polymeric Materials of the Russian Academy of Sciences, Profsoyuznaya 70, Moscow, 117393, Russia.,Chemistry Department, Moscow State University, 1/3 Leninskie Gory, Moscow, 119991, Russia
| | - Wenyan Yang
- The Institute for Advanced Studies, Wuhan University, Wuhan City, 430072, Hubei Province, China
| | - Nikolay M Surin
- Enikolopov Institute of Synthetic Polymeric Materials of the Russian Academy of Sciences, Profsoyuznaya 70, Moscow, 117393, Russia
| | - Olivier Douhéret
- Materia Nova R&D Center, Avenue Nicolas Copernic 3, 7000, Mons, Belgium
| | - Jie Min
- The Institute for Advanced Studies, Wuhan University, Wuhan City, 430072, Hubei Province, China.,Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, Zhengzhou, 450002, China
| | - Thomas L C Jansen
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands
| | - Sergei A Ponomarenko
- Enikolopov Institute of Synthetic Polymeric Materials of the Russian Academy of Sciences, Profsoyuznaya 70, Moscow, 117393, Russia.,Chemistry Department, Moscow State University, 1/3 Leninskie Gory, Moscow, 119991, Russia
| | - Maxim S Pshenichnikov
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands.
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6
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Lee CK, Willard AP. Representing the Molecular Signatures of Disordered Molecular Semiconductors in Size-Extendable Models of Exciton Dynamics. J Phys Chem B 2020; 124:5238-5245. [PMID: 32422051 DOI: 10.1021/acs.jpcb.0c02898] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This manuscript presents an approach to developing size-extendable phenomenological site-based models for simulating exciton dynamics in disordered organic molecular semiconducting materials. This approach extends an existing methodology that assigns the parameters of the time-dependent Frenkel exciton model by applying fragmentation-based electronic structure calculations to the output of classical molecular dynamics simulations. This methodology is inherently limited by the system size of the all-atom simulation, which is well below the performance capability of site-based models. Here, we demonstrate that this system size limitation can be effectively overcome by defining a size-extendable surrogate model based on the correlated parameter statistics derived from existing fragmentation-based methods. We demonstrate our approach on a monolayer film of sexithiophene molecules, first validating the accuracy of the surrogate system in reproducing exciton dynamical properties of a 150 molecule system, then extending it to systems of 2500 molecules. With this extended system, we explore the sensitivity of exciton dynamics to variations in the temperature as well as the amplitude and spatial correlations of energetic disorder. We conclude that exciton dynamics can be significantly enhanced in morphologies with spatially correlated molecular configurations but only if the overall distribution of site energies is sufficiently broad.
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Affiliation(s)
- Chee Kong Lee
- Tencent America, Palo Alto, California 94306, United States
| | - Adam P Willard
- Department of Chemistry, MIT, Cambridge, Massachusetts 02139, United States
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7
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Chen Z, Chen X, Qiu B, Zhou G, Jia Z, Tao W, Li Y, Yang YM, Zhu H. Ultrafast Hole Transfer and Carrier Transport Controlled by Nanoscale-Phase Morphology in Nonfullerene Organic Solar Cells. J Phys Chem Lett 2020; 11:3226-3233. [PMID: 32259443 DOI: 10.1021/acs.jpclett.0c00919] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Nonfullerene acceptors (NFAs) have attracted great attention in high-efficiency organic solar cells (OSCs). While the effect of molecular properties including structures and energetics on charge transfer has been extensively investigated, the effect of macroscopic-phase properties is yet to be revealed. Here we have performed a correlation study of the nanoscale-phase morphology on the photoexcited hole transfer (HT) process and photovoltaic performance by combining ultrafast spectroscopy with high temporal resolution and photo-induced force microscopy (PiFM) with high spatial and chemical resolution. In PM6/IT-4F, we observe biphasic HT behavior with a minor ultrafast (<100 fs) interfacial process and a major diffusion-mediated HT process until ∼100 ps, which depends strongly on phase segregation. Because of the interplay between charge transfer and transport, a compromised domain size of 20-30 nm for NFAs shows the best performance. This study highlights the critical role of phase morphology in high-efficiency OSCs.
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Affiliation(s)
| | | | - Beibei Qiu
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | | | | | | | - Yongfang Li
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
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8
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Yurash B, Nakanotani H, Olivier Y, Beljonne D, Adachi C, Nguyen TQ. Photoluminescence Quenching Probes Spin Conversion and Exciton Dynamics in Thermally Activated Delayed Fluorescence Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1804490. [PMID: 30957291 DOI: 10.1002/adma.201804490] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 09/05/2018] [Indexed: 06/09/2023]
Abstract
Fluorescent materials that efficiently convert triplet excitons into singlets through reverse intersystem crossing (RISC) rival the efficiencies of phosphorescent state-of-the-art organic light-emitting diodes. This upconversion process, a phenomenon known as thermally activated delayed fluorescence (TADF), is dictated by the rate of RISC, a material-dependent property that is challenging to determine experimentally. In this work, a new analytical model is developed which unambiguously determines the magnitude of RISC, as well as several other important photophysical parameters such as exciton diffusion coefficients and lengths, all from straightforward time-resolved photoluminescence measurements. From a detailed investigation of five TADF materials, important structure-property relationships are derived and a brominated derivative of 2,4,5,6-tetrakis(carbazol-9-yl)isophthalonitrile that has an exciton diffusion length of over 40 nm and whose excitons interconvert between the singlet and triplet states ≈36 times during one lifetime is identified.
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Affiliation(s)
- Brett Yurash
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, 93106, USA
| | - Hajime Nakanotani
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395, Japan
| | - Yoann Olivier
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000, Mons, Belgium
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000, Mons, Belgium
| | - Chihaya Adachi
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395, Japan
| | - Thuc-Quyen Nguyen
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, 93106, USA
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9
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Xue W, Lin JY, Liu B, Shi NE, Yu MN, Wu WD, Zhu WS, Xie LH, Wang LH, Huang W. Exploring side-chain length effect on β-phase of polyfluorene derivatives in electrospinning and their optical behavior. POLYMER 2018. [DOI: 10.1016/j.polymer.2018.05.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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10
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Chowdhury M, Sajjad MT, Savikhin V, Hergué N, Sutija KB, Oosterhout SD, Toney MF, Dubois P, Ruseckas A, Samuel IDW. Tuning crystalline ordering by annealing and additives to study its effect on exciton diffusion in a polyalkylthiophene copolymer. Phys Chem Chem Phys 2018; 19:12441-12451. [PMID: 28470282 DOI: 10.1039/c7cp00877e] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The influence of various processing conditions on the singlet exciton diffusion is explored in films of a conjugated random copolymer poly-(3-hexylthiophene-co-3-dodecylthiophene) (P3HT-co-P3DDT) and correlated with the degree of crystallinity probed by grazing incidence X-ray scattering and with exciton bandwidth determined from absorption spectra. The exciton diffusion coefficient is deduced from exciton-exciton annihilation measurements and is found to increase by more than a factor of three when thin films are annealed using CS2 solvent vapour. A doubling of exciton diffusion coefficient is observed upon melt annealing at 200 °C and the corresponding films show about 50% enhancement in the degree of crystallinity. In contrast, films fabricated from polymer solutions containing a small amount of either solvent additive or nucleating agent show a decrease in exciton diffusion coefficient possibly due to formation of traps for excitons. Our results suggest that the enhancement of exciton diffusivity occurs because of increased crystallinity of alkyl-stacking and longer conjugation of aggregated chains which reduces the exciton bandwidth.
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Affiliation(s)
- Mithun Chowdhury
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS, UK.
| | - Muhammad T Sajjad
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS, UK.
| | - Victoria Savikhin
- Stanford Synchrotron Radiation Lightsource, Menlo Park, CA 94025, USA and Stanford Electrical Engineering Department, Stanford, CA 94305, USA
| | - Noémie Hergué
- Laboratory of Polymeric and Composite Materials, University de Mons, Mons, Belgium
| | - Karina B Sutija
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS, UK.
| | | | - Michael F Toney
- Stanford Synchrotron Radiation Lightsource, Menlo Park, CA 94025, USA
| | - Philippe Dubois
- Laboratory of Polymeric and Composite Materials, University de Mons, Mons, Belgium
| | - Arvydas Ruseckas
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS, UK.
| | - Ifor D W Samuel
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS, UK.
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11
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Promoting Singlet/triplet Exciton Transformation in Organic Optoelectronic Molecules: Role of Excited State Transition Configuration. Sci Rep 2017; 7:6225. [PMID: 28740201 PMCID: PMC5524908 DOI: 10.1038/s41598-017-05339-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 05/26/2017] [Indexed: 11/28/2022] Open
Abstract
Exciton transformation, a non-radiative process in changing the spin multiplicity of an exciton usually between singlet and triplet forms, has received much attention recently due to its crucial effects in manipulating optoelectronic properties for various applications. However, current understanding of exciton transformation mechanism does not extend far beyond a thermal equilibrium of two states with different multiplicity and it is a significant challenge to probe what exactly control the transformation between the highly active excited states. Here, based on the recent developments of three types of purely organic molecules capable of efficient spin-flipping, we perform ab initio structure/energy optimization and similarity/overlap extent analysis to theoretically explore the critical factors in controlling the transformation process of the excited states. The results suggest that the states having close energy levels and similar exciton characteristics with same transition configurations and high heteroatom participation are prone to facilitating exciton transformation. A basic guideline towards the molecular design of purely organic materials with facile exciton transformation ability is also proposed. Our discovery highlights systematically the critical importance of vertical transition configuration of excited states in promoting the singlet/triplet exciton transformation, making a key step forward in excited state tuning of purely organic optoelectronic materials.
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12
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Long Y, Hedley GJ, Ruseckas A, Chowdhury M, Roland T, Serrano LA, Cooke G, Samuel IDW. Effect of Annealing on Exciton Diffusion in a High Performance Small Molecule Organic Photovoltaic Material. ACS APPLIED MATERIALS & INTERFACES 2017; 9:14945-14952. [PMID: 28358189 PMCID: PMC5423077 DOI: 10.1021/acsami.6b16487] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 03/30/2017] [Indexed: 05/29/2023]
Abstract
Singlet exciton diffusion was studied in the efficient organic photovoltaic electron donor material DTS(FBTTh2)2. Three complementary time-resolved fluorescence measurements were performed: quenching in planar heterojunctions with an electron acceptor, exciton-exciton annihilation, and fluorescence depolarization. The average exciton diffusivity increases upon annealing from 1.6 × 10-3 to 3.6 × 10-3 cm2 s-1, resulting in an enhancement of the mean two-dimensional exciton diffusion length (LD = (4Dτ)1/2) from 15 to 27 nm. About 30% of the excitons get trapped very quickly in as-cast films. The high exciton diffusion coefficient of the material leads to it being able to harvest excitons efficiently from large donor domains in bulk heterojunctions.
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Affiliation(s)
- Yun Long
- Organic Semiconductor
Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, United Kingdom
| | - Gordon J. Hedley
- Organic Semiconductor
Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, United Kingdom
| | - Arvydas Ruseckas
- Organic Semiconductor
Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, United Kingdom
| | - Mithun Chowdhury
- Organic Semiconductor
Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, United Kingdom
| | - Thomas Roland
- Organic Semiconductor
Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, United Kingdom
| | - Luis A Serrano
- Glasgow
Centre for Physical Organic Chemistry, WESTCHEM, School of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Graeme Cooke
- Glasgow
Centre for Physical Organic Chemistry, WESTCHEM, School of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Ifor D. W. Samuel
- Organic Semiconductor
Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, United Kingdom
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Sajjad M, Ward AJ, Kästner C, Ruseckas A, Hoppe H, Samuel IDW. Controlling Exciton Diffusion and Fullerene Distribution in Photovoltaic Blends by Side Chain Modification. J Phys Chem Lett 2015; 6:3054-60. [PMID: 26267202 PMCID: PMC4565514 DOI: 10.1021/acs.jpclett.5b01059] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The influence of crystallinity on exciton diffusion and fullerene distribution was investigated by blending amorphous and semicrystalline copolymers. We measured exciton diffusion and fluorescence quenching in such blends by dispersing fullerene molecules into them. We find that the diffusion length is more than two times higher in the semicrystalline copolymer than in the amorphous copolymer. We also find that fullerene preferentially mixes into disordered regions of the polymer film. This shows that relatively small differences in molecular structure are important for exciton diffusion and fullerene distribution.
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Affiliation(s)
- Muhammad
T. Sajjad
- Organic
Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, KY16 9SS, United Kingdom
| | - Alexander J. Ward
- Organic
Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, KY16 9SS, United Kingdom
| | - Christian Kästner
- Institute
of Physics, Technische Universität
Ilmenau, Langewiesener
Straße 22, 98693 Ilmenau, Germany
- Institute
of Thermodynamics and Fluid Mechanics, Technische
Universität Ilmenau, Helmholtzring 1, 98693 Ilmenau, Germany
| | - Arvydas Ruseckas
- Organic
Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, KY16 9SS, United Kingdom
| | - Harald Hoppe
- Institute
of Physics, Technische Universität
Ilmenau, Langewiesener
Straße 22, 98693 Ilmenau, Germany
- Center
for Energy and Environmental Chemistry Jena (CEEC Jena), Friedrich Schiller University Jena, Philosphenweg 7a, 07743 Jena, Germany
- Laboratory
of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstrasse 10, 07743 Jena, Germany
| | - Ifor D. W. Samuel
- Organic
Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, KY16 9SS, United Kingdom
- E-mail:
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