1
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Kay AM, Riley DB, Meredith P, Armin A, Sandberg OJ. A New Framework for Understanding Recombination-Limited Charge Extraction in Disordered Semiconductors. J Phys Chem Lett 2024; 15:4416-4421. [PMID: 38626394 PMCID: PMC11057038 DOI: 10.1021/acs.jpclett.4c00218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 04/05/2024] [Accepted: 04/10/2024] [Indexed: 04/18/2024]
Abstract
Recombination of free charges is a key loss mechanism limiting the performance of organic semiconductor-based photovoltaics such as solar cells and photodetectors. The carrier density-dependence of the rate of recombination and the associated rate coefficients are often estimated using transient charge extraction (CE) experiments. These experiments, however, often neglect the effect of recombination during the transient extraction process. In this work, the validity of the CE experiment for low-mobility devices, such as organic semiconductor-based photovoltaics, is investigated using transient drift-diffusion simulations. We find that recombination leads to incomplete CE, resulting in carrier density-dependent recombination rate constants and overestimated recombination orders; an effect that depends on both the charge carrier mobilities and the resistance-capacitance time constant. To overcome this intrinsic limitation of the CE experiment, we present an analytical model that accounts for charge carrier recombination, validate it using numerical simulations, and employ it to correct the carrier density-dependence observed in experimentally determined bimolecular recombination rate constants.
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Affiliation(s)
- Austin M. Kay
- Sustainable
Advanced Materials (Sêr-SAM), Centre for Integrative Semiconductor
Materials (CISM), Department of Physics, Swansea University Bay Campus, Swansea SA1 8EN, United Kingdom
| | - Drew B. Riley
- Sustainable
Advanced Materials (Sêr-SAM), Centre for Integrative Semiconductor
Materials (CISM), Department of Physics, Swansea University Bay Campus, Swansea SA1 8EN, United Kingdom
| | - Paul Meredith
- Sustainable
Advanced Materials (Sêr-SAM), Centre for Integrative Semiconductor
Materials (CISM), Department of Physics, Swansea University Bay Campus, Swansea SA1 8EN, United Kingdom
| | - Ardalan Armin
- Sustainable
Advanced Materials (Sêr-SAM), Centre for Integrative Semiconductor
Materials (CISM), Department of Physics, Swansea University Bay Campus, Swansea SA1 8EN, United Kingdom
| | - Oskar J. Sandberg
- Physics,
Faculty of Science and Engineering, Åbo
Akademi University, 20500 Turku, Finland
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2
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Du Z, Luong HM, Sabury S, Jones AL, Zhu Z, Panoy P, Chae S, Yi A, Kim HJ, Xiao S, Brus VV, Manjunatha Reddy GN, Reynolds JR, Nguyen TQ. High-Performance Wearable Organic Photodetectors by Molecular Design and Green Solvent Processing for Pulse Oximetry and Photoplethysmography. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2310478. [PMID: 38054854 DOI: 10.1002/adma.202310478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 11/27/2023] [Indexed: 12/07/2023]
Abstract
White-light detection from the visible to the near-infrared region is central to many applications such as high-speed cameras, autonomous vehicles, and wearable electronics. While organic photodetectors (OPDs) are being developed for such applications, several challenges must be overcome to produce scalable high-detectivity OPDs. This includes issues associated with low responsivity, narrow absorption range, and environmentally friendly device fabrication. Here, an OPD system processed from 2-methyltetrahydrofuran (2-MeTHF) sets a record in light detectivity, which is also comparable with commercially available silicon-based photodiodes is reported. The newly designed OPD is employed in wearable devices to monitor heart rate and blood oxygen saturation using a flexible OPD-based finger pulse oximeter. In achieving this, a framework for a detailed understanding of the structure-processing-property relationship in these OPDs is also developed. The bulk heterojunction (BHJ) thin films processed from 2-MeTHF are characterized at different length scales with advanced techniques. The BHJ morphology exhibits optimal intermixing and phase separation of donor and acceptor moieties, which facilitates the charge generation and collection process. Benefitting from high charge carrier mobilities and a low shunt leakage current, the newly developed OPD exhibits a specific detectivity of above 1012 Jones over 400-900 nm, which is higher than those of reference devices processed from chlorobenzene and ortho-xylene.
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Affiliation(s)
- Zhifang Du
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Hoang Mai Luong
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Sina Sabury
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Austin L Jones
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Ziyue Zhu
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Patchareepond Panoy
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Sangmin Chae
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Ahra Yi
- Department of Organic Materials Science and Engineering, School of Chemical Engineering, Pusan National University, Busan, 46241, Republic of Korea
| | - Hyo Jung Kim
- Department of Organic Materials Science and Engineering, School of Chemical Engineering, Pusan National University, Busan, 46241, Republic of Korea
| | - Steven Xiao
- 1-Material Inc, 2290 Chemin St-Francois, Dorval, Quebec, H9P 1K2, Canada
| | - Viktor V Brus
- Department of Physics, School of Sciences and Humanities, Nazarbayev University, Nur-Sultan City, 010000, Republic of Kazakhstan
| | - G N Manjunatha Reddy
- University of Lille, CNRS, Centrale Lille Institut, Univ. Artois, UMR 8181, Unité de Catalyse et Chimie du Solide, Lille, F-59000, France
| | - John R Reynolds
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Thuc-Quyen Nguyen
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, CA, 93106, USA
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3
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Xie C, Liang S, Zhang G, Li S. Water-Processed Organic Solar Cell with Efficiency Exceeding 11. Polymers (Basel) 2022; 14:polym14194229. [PMID: 36236177 PMCID: PMC9573733 DOI: 10.3390/polym14194229] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 10/03/2022] [Accepted: 10/04/2022] [Indexed: 11/16/2022] Open
Abstract
Water processing is an ideal strategy for the ecofriendly fabrication of organic photovoltaics (OPVs) and exhibits a strong market-driven demand. Here, we report a state-of-the-art active material, namely PM6:BTP-eC9, for the synthesis of water-borne nanoparticle (NP) dispersion towards ecofriendly OPV fabrication. The surfactant-stripping technique, combined with a poloxamer, facilitates purification and eliminates excess surfactant in water-dispersed organic semiconducting NPs. The introduction of 1,8-diiodooctane (DIO) for the synthesis of surfactant-stripped NP (ssNP) further promotes a percolated microstructure of the polymer and NFA in each ssNP, yielding water-processed OPVs with a record efficiency of over 11%. The use of an additive during water-borne ssNP synthesis is a promising strategy for morphology optimization in NP OPVs. It is believed that the findings in this work will engender more research interest and effort relating to water-processing in preparation of the industrial production of OPVs.
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4
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Zeiske S, Sandberg OJ, Kurpiers J, Shoaee S, Meredith P, Armin A. Probing Charge Generation Efficiency in Thin-Film Solar Cells by Integral-Mode Transient Charge Extraction. ACS PHOTONICS 2022; 9:1188-1195. [PMID: 35571262 PMCID: PMC9097587 DOI: 10.1021/acsphotonics.1c01532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Indexed: 06/15/2023]
Abstract
The photogeneration of free charges in light-harvesting devices is a multistep process, which can be challenging to probe due to the complexity of contributing energetic states and the competitive character of different driving mechanisms. In this contribution, we advance a technique, integral-mode transient charge extraction (ITCE), to probe these processes in thin-film solar cells. ITCE combines capacitance measurements with the integral-mode time-of-flight method in the low intensity regime of sandwich-type thin-film devices and allows for the sensitive determination of photogenerated charge-carrier densities. We verify the theoretical framework of our method by drift-diffusion simulations and demonstrate the applicability of ITCE to organic and perovskite semiconductor-based thin-film solar cells. Furthermore, we examine the field dependence of charge generation efficiency and find our ITCE results to be in excellent agreement with those obtained via time-delayed collection field measurements conducted on the same devices.
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Affiliation(s)
- Stefan Zeiske
- Sustainable
Advanced Materials (Sêr-SAM), Department of Physics, Swansea University, Singleton Park, Swansea SA2 8PP, Wales, United Kingdom
| | - Oskar J. Sandberg
- Sustainable
Advanced Materials (Sêr-SAM), Department of Physics, Swansea University, Singleton Park, Swansea SA2 8PP, Wales, United Kingdom
| | - Jona Kurpiers
- Disordered Semiconductor Optoelectronics,
Institute
of Physics and Astronomy, University Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany
| | - Safa Shoaee
- Disordered Semiconductor Optoelectronics,
Institute
of Physics and Astronomy, University Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany
| | - Paul Meredith
- Sustainable
Advanced Materials (Sêr-SAM), Department of Physics, Swansea University, Singleton Park, Swansea SA2 8PP, Wales, United Kingdom
| | - Ardalan Armin
- Sustainable
Advanced Materials (Sêr-SAM), Department of Physics, Swansea University, Singleton Park, Swansea SA2 8PP, Wales, United Kingdom
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5
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Alqahtani O, Hosseini SM, Ferron T, Murcia V, McAfee T, Vixie K, Huang F, Armin A, Shoaee S, Collins BA. Evidence That Sharp Interfaces Suppress Recombination in Thick Organic Solar Cells. ACS APPLIED MATERIALS & INTERFACES 2021; 13:56394-56403. [PMID: 34787408 DOI: 10.1021/acsami.1c15570] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Commercialization and scale-up of organic solar cells (OSCs) using industrial solution printing require maintaining maximum performance at active-layer thicknesses >400 nm─a characteristic still not generally achieved in non-fullerene acceptor OSCs. NT812/PC71BM is a rare system, whose performance increases up to these thicknesses due to highly suppressed charge recombination relative to the classic Langevin model. The suppression in this system, however, uniquely depends on device processing, pointing toward the role of nanomorphology. We investigate the morphological origins of this suppressed recombination by combining results from a suite of X-ray techniques. We are surprised to find that while all investigated devices are composed of pure, similarly aggregated nanodomains, Langevin reduction factors can still be tuned from ∼2 to >1000. This indicates that pure aggregated phases are insufficient for non-Langevin (reduced) recombination. Instead, we find that large well-ordered conduits and, in particular, sharp interfaces between domains appear to help to keep opposite charges separated and percolation pathways clear for enhanced charge collection in thick active layers. To our knowledge, this is the first quantitative study to isolate the donor/acceptor interfacial width correlated with non-Langevin charge recombination. This new structure-property relationship will be key to successful commercialization of printed OSCs at scale.
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Affiliation(s)
- Obaid Alqahtani
- Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164, United States
- Department of Physics, Prince Sattam Bin Abdulaziz University, Alkharj 11942, KSA
| | - Seyed Mehrdad Hosseini
- Optoelectronics of Organic Semiconductors Institute, University of Potsdam, Potsdam-Golm 14476, Germany
| | - Thomas Ferron
- Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, United States
| | - Victor Murcia
- Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164, United States
| | - Terry McAfee
- Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, United States
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Kevin Vixie
- Department of Mathematics, Washington State University, Pullman, Washington 99164, United States
| | - Fei Huang
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China
| | - Ardalan Armin
- Department of Physics, Swansea University, Singleton Park, Swansea, Wales SA2 8PP, U.K
| | - Safa Shoaee
- Optoelectronics of Organic Semiconductors Institute, University of Potsdam, Potsdam-Golm 14476, Germany
| | - Brian A Collins
- Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164, United States
- Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, United States
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6
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Madhu M, Ramakrishnan R, Vijay V, Hariharan M. Free Charge Carriers in Homo-Sorted π-Stacks of Donor-Acceptor Conjugates. Chem Rev 2021; 121:8234-8284. [PMID: 34133137 DOI: 10.1021/acs.chemrev.1c00078] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Inspired by the high photoconversion efficiency observed in natural light-harvesting systems, the hierarchical organization of molecular building blocks has gained impetus in the past few decades. Particularly, the molecular arrangement and packing in the active layer of organic solar cells (OSCs) have garnered significant attention due to the decisive role of the nature of donor/acceptor (D/A) heterojunctions in charge carrier generation and ultimately the power conversion efficiency. This review focuses on the recent developments in emergent optoelectronic properties exhibited by self-sorted donor-on-donor/acceptor-on-acceptor arrangement of covalently linked D-A systems, highlighting the ultrafast excited state dynamics of charge transfer and transport. Segregated organization of donors and acceptors promotes the delocalization of photoinduced charges among the stacks, engendering an enhanced charge separation lifetime and percolation pathways with ambipolar conductivity and charge carrier yield. Covalently linking donors and acceptors ensure a sufficient D-A interface and interchromophoric electronic coupling as required for faster charge separation while providing better control over their supramolecular assemblies. The design strategies to attain D-A conjugate assemblies with optimal charge carrier generation efficiency, the scope of their application compared to state-of-the-art OSCs, current challenges, and future opportunities are discussed in the review. An integrated overview of rational design approaches derived from the comprehension of underlying photoinduced processes can pave the way toward superior optoelectronic devices and bring in new possibilities to the avenue of functional supramolecular architectures.
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Affiliation(s)
- Meera Madhu
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Vithura, Thiruvananthapuram, Kerala, India 695551
| | - Remya Ramakrishnan
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Vithura, Thiruvananthapuram, Kerala, India 695551
| | - Vishnu Vijay
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Vithura, Thiruvananthapuram, Kerala, India 695551
| | - Mahesh Hariharan
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Vithura, Thiruvananthapuram, Kerala, India 695551
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7
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Dhakal P, Ferron T, Alotaibi A, Murcia V, Alqahtani O, Collins BA. Evidence for Field-Dependent Charge Separation Caused by Mixed Phases in Polymer-Fullerene Organic Solar Cells. J Phys Chem Lett 2021; 12:1847-1853. [PMID: 33577332 DOI: 10.1021/acs.jpclett.0c03863] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
As organic photovoltaic performance approaches 20% efficiencies, causal structure-performance relationships must be established for devices to realize theoretical limits and become commercially competitive. Here, we reveal evidence of a causal relationship between mixed donor-acceptor interfaces and charge generation in polymer-fullerene solar cells. To do this, we combine a holistic loss analysis of device performance with quantitative synchrotron X-ray nanocharacterization to identify a >98% anticorrelation between field-dependent geminate recombination and nanodomain purity. Importantly, our analysis eliminates other possible explanations of the performance trends, a requirement to establish causality. The unprecedented granular level of our analysis also separates field-dependent and field-independent recombination at the interface, where we find for the first time that this system is free of field-independent recombination, a loss channel that plagues high-performance systems, including those with non-fullerene acceptors. This result broadens the case that minimizing mixed phases to promote sharp interfaces between pure aggregated domains is the ideal nanostructure for realizing theoretical efficiency limits of organic photovoltaics.
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Affiliation(s)
- Prabodh Dhakal
- Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, United States
| | - Thomas Ferron
- Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, United States
| | - Awwad Alotaibi
- Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164, United States
| | - Victor Murcia
- Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164, United States
| | - Obaid Alqahtani
- Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164, United States
- Department of Physics, Prince Sattam bin Abdulaziz University, Alkharj, 11942, Kingdom of Saudi Arabia
| | - Brian A Collins
- Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, United States
- Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164, United States
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8
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Schwarz KN, Mitchell VD, Khan SUZ, Lee C, Reinhold A, Smith TA, Ghiggino KP, Jones DJ, Rand BP, Scholes GD. Morphological Requirements for Nanoscale Electric Field Buildup in a Bulk Heterojunction Solar Cell. J Phys Chem Lett 2021; 12:537-545. [PMID: 33378206 DOI: 10.1021/acs.jpclett.0c03425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The morphology of organic semiconductors is critical to their function in optoelectronic devices and is particularly crucial in the donor-acceptor mixture that comprises the bulk heterojunction of organic solar cells. Here, energy landscapes can play integral roles in charge photogeneration, and recently have been shown to drive the accumulation of charge carriers away from the interface, resulting in the buildup of large nanoscale electric fields, much like a capacitor. In this work we combine morphological and spectroscopic data to outline the requirements for this interdomain charge accumulation, finding that this effect is driven by a three-phase morphology that creates an energetic cascade for charge carriers. By adjusting annealing conditions, we show that domain purity, but not size, is critical for an electro-absorption feature to grow-in. This demonstrates that the energy landscape around the interface shapes the movement of charges and that pure domains are required for charge carrier buildup that results in reduced recombination and large interdomain nanoscale electric fields.
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Affiliation(s)
- Kyra N Schwarz
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Valerie D Mitchell
- Australian Synchrotron, 800 Blackburn Road, Clayton, VIC 3168, Australia
| | | | | | - Adam Reinhold
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | | | | | | | | | - Gregory D Scholes
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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9
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Karuthedath S, Gorenflot J, Melianas A, Kan Z, Kemerink M, Laquai F. Buildup of Triplet-State Population in Operating TQ1:PC 71BM Devices Does Not Limit Their Performance. J Phys Chem Lett 2020; 11:2838-2845. [PMID: 32202789 DOI: 10.1021/acs.jpclett.0c00756] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Triplet generation in organic solar cells has been considered a major loss channel. Determining the density of the triplet-state population in an operating device is challenging. Here, we employ transient absorption (TA) spectroscopy on the quinoxaline-thiophene copolymer TQ1 blended with PC71BM, quantify the transient charge and triplet-state densities, and parametrize their generation and recombination dynamics. The charge recombination parameters reproduce the experimentally measured current-voltage characteristics in charge carrier drift-diffusion simulations, and they yield the steady-state charge densities. We demonstrate that triplets are formed by both geminate and nongeminate recombination of charge carriers and decay primarily by triplet-triplet annihilation. Using the charge densities in the rate equations describing triplet-state dynamics, we find that triplet-state densities in devices are in the range of charge carrier densities. Despite this substantial triplet-state buildup, TQ1:PC71BM devices exhibit only moderate geminate recombination and significantly reduced nongeminate charge recombination, with reduction factors between 10-4 and 10-3 compared to Langevin recombination.
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Affiliation(s)
- Safakath Karuthedath
- Materials Science and Engineering Program (MSE), Physical Sciences and Engineering Division (PSE), KAUST Solar Center (KSC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Julien Gorenflot
- Materials Science and Engineering Program (MSE), Physical Sciences and Engineering Division (PSE), KAUST Solar Center (KSC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Armantas Melianas
- Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics, Center of Organic Electronics (COE), Linköping University, 58183 Linköping, Sweden
| | - Zhipeng Kan
- Materials Science and Engineering Program (MSE), Physical Sciences and Engineering Division (PSE), KAUST Solar Center (KSC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Martijn Kemerink
- Complex Materials and Devices, Department of Physics, Chemistry and Biology, Linköping University, 58183 Linköping, Sweden
| | - Frédéric Laquai
- Materials Science and Engineering Program (MSE), Physical Sciences and Engineering Division (PSE), KAUST Solar Center (KSC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
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10
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Yin A, Zhang D, Wang J, Zhou H, Fu Z, Zhang Y. Mediated Non-geminate Recombination in Ternary Organic Solar Cells Through a Liquid Crystal Guest Donor. Front Chem 2020; 8:21. [PMID: 32117865 PMCID: PMC7026665 DOI: 10.3389/fchem.2020.00021] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 01/09/2020] [Indexed: 11/13/2022] Open
Abstract
The approach via ternary blends prompts the increase of absorbed photon density and resultant photocurrent enhancement in organic solar cells (OSCs). In contrast to actively reported high efficiency ternary OSCs, little is known about charge recombination properties and carrier loss mechanisms in these emerging devices. Here, through introducing a small molecule donor BTR as a guest component to the PCE-10:PC71BM binary system, we show that photocarrier losses via recombination are mitigated with respect the binary OSCs, owing to a reduced bimolecular recombination. The gain of the fill factor in ternary devices are reconciled by the change in equilibrium between charge exaction and recombination in the presence of BTR toward the former process. With these modifications, the power conversion efficiency in ternary solar cells receives a boost from 8.8 (PCE-10:PC71BM) to 10.88%. We further found that the voltage losses in the ternary cell are slightly suppressed, related to the rising charge transfer-state energy. These benefits brought by the third guest donor are important for attaining improvements on key photophysical processes governing the photovoltaic efficiencies in organic ternary solar cells.
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Affiliation(s)
- Ao Yin
- School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China
| | - Dongyang Zhang
- School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China
| | - Jianqiu Wang
- School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China
| | - Huiqiong Zhou
- CAS Key Laboratory of Nanosystem and Hierachical Fabrication CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, China
| | - Zhiqiang Fu
- School of Engineering and Technology, China University of Geosciences, Beijing, China
| | - Yuan Zhang
- School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China
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11
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Kaiser W, Gagliardi A. Kinetic Monte Carlo Study of the Role of the Energetic Disorder on the Open-Circuit Voltage in Polymer/Fullerene Solar Cells. J Phys Chem Lett 2019; 10:6097-6104. [PMID: 31533434 DOI: 10.1021/acs.jpclett.9b02144] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
One major factor limiting the efficiency in organic solar cells (OSCs) is the low open-circuit voltage (Voc). Existing theoretical studies link the Voc with the charge transfer (CT) state and nonradiative recombination. However, also morphology and energetic disorder can have a strong impact on the Voc within realistic bulk-heterojunction OSCs. In this work, we present a kinetic Monte Carlo study on the role of the energetic disorder on the maximum Voc. We compute the quasi-Fermi level splitting for different energetic disorder and analyze the impact of the energetic disorder at the donor-acceptor interface as well as correlations in the site energies on the Voc. Our results show that the interface strongly controls the maximum Voc. For a higher interface disorder, charge densities and nongeminate recombination increase and the Voc is reduced. Furthermore, the correlated morphologies show an increase in the maximum Voc and a reduced impact of the energetic disorder.
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Affiliation(s)
- W Kaiser
- Department of Electrical and Computer Engineering , Technical University of Munich , Karlstraße 45 , 80333 Munich , Germany
| | - A Gagliardi
- Department of Electrical and Computer Engineering , Technical University of Munich , Karlstraße 45 , 80333 Munich , Germany
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12
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Zhang S, Hosseini SM, Gunder R, Petsiuk A, Caprioglio P, Wolff CM, Shoaee S, Meredith P, Schorr S, Unold T, Burn PL, Neher D, Stolterfoht M. The Role of Bulk and Interface Recombination in High-Efficiency Low-Dimensional Perovskite Solar Cells. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1901090. [PMID: 31166640 DOI: 10.1002/adma.201901090] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Revised: 04/25/2019] [Indexed: 06/09/2023]
Abstract
2D Ruddlesden-Popper perovskite (RPP) solar cells have excellent environmental stability. However, the power conversion efficiency (PCE) of RPP cells remains inferior to 3D perovskite-based cells. Herein, 2D (CH3 (CH2 )3 NH3 )2 (CH3 NH3 )n -1 Pbn I3 n +1 perovskite cells with different numbers of [PbI6 ]4- sheets (n = 2-4) are analyzed. Photoluminescence quantum yield (PLQY) measurements show that nonradiative open-circuit voltage (VOC ) losses outweigh radiative losses in materials with n > 2. The n = 3 and n = 4 films exhibit a higher PLQY than the standard 3D methylammonium lead iodide perovskite although this is accompanied by increased interfacial recombination at the top perovskite/C60 interface. This tradeoff results in a similar PLQY in all devices, including the n = 2 system where the perovskite bulk dominates the recombination properties of the cell. In most cases the quasi-Fermi level splitting matches the device VOC within 20 meV, which indicates minimal recombination losses at the metal contacts. The results show that poor charge transport rather than exciton dissociation is the primary reason for the reduction in fill factor of the RPP devices. Optimized n = 4 RPP solar cells had PCEs of 13% with significant potential for further improvements.
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Affiliation(s)
- Shanshan Zhang
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476, Potsdam-Golm, Germany
- Centre for Organic Photonics and Electronics (COPE), School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, 4072, Australia
| | - Seyed M Hosseini
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476, Potsdam-Golm, Germany
| | - René Gunder
- Department of Structure and Dynamics of Energy Materials, Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109, Berlin, Germany
| | - Andrei Petsiuk
- Department of Structure and Dynamics of Energy Materials, Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109, Berlin, Germany
| | - Pietro Caprioglio
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476, Potsdam-Golm, Germany
- Young Investigator Group Perovskite Tandem Solar Cells, Helmholtz-Zentrum Berlin, Kekuléstr. 5, 12489, Berlin, Germany
| | - Christian M Wolff
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476, Potsdam-Golm, Germany
| | - Safa Shoaee
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476, Potsdam-Golm, Germany
| | - Paul Meredith
- Department of Physics, Swansea University, Singleton Park, Swansea, SA2 8PP, Wales, UK
| | - Susan Schorr
- Department of Structure and Dynamics of Energy Materials, Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109, Berlin, Germany
| | - Thomas Unold
- Department of Structure and Dynamics of Energy Materials, Helmholtz-Zentrum-Berlin, Hahn-Meitner-Platz 1, D-14109, Berlin, Germany
| | - Paul L Burn
- Centre for Organic Photonics and Electronics (COPE), School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, 4072, Australia
| | - Dieter Neher
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476, Potsdam-Golm, Germany
| | - Martin Stolterfoht
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476, Potsdam-Golm, Germany
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13
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Dimitrov SD, Azzouzi M, Wu J, Yao J, Dong Y, Tuladhar PS, Schroeder BC, Bittner ER, McCulloch I, Nelson J, Durrant JR. Spectroscopic Investigation of the Effect of Microstructure and Energetic Offset on the Nature of Interfacial Charge Transfer States in Polymer: Fullerene Blends. J Am Chem Soc 2019; 141:4634-4643. [PMID: 30807130 PMCID: PMC6429453 DOI: 10.1021/jacs.8b11484] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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Despite
performance improvements of organic photovoltaics, the
mechanism of photoinduced electron–hole separation at organic
donor–acceptor interfaces remains poorly understood. Inconclusive
experimental and theoretical results have produced contradictory models
for electron–hole separation in which the role of interfacial
charge-transfer (CT) states is unclear, with one model identifying
them as limiting separation and another as readily dissociating. Here,
polymer–fullerene blends with contrasting photocurrent properties
and enthalpic offsets driving separation were studied. By modifying
composition, film structures were varied from consisting of molecularly
mixed polymer–fullerene domains to consisting of both molecularly
mixed and fullerene domains. Transient absorption spectroscopy revealed
that CT state dissociation generating separated electron–hole
pairs is only efficient in the high energy offset blend with fullerene
domains. In all other blends (with low offset or predominantly molecularly
mixed domains), nanosecond geminate electron–hole recombination
is observed revealing the importance of spatially localized electron–hole
pairs (bound CT states) in the electron–hole dynamics. A two-dimensional
lattice exciton model was used to simulate the excited state spectrum
of a model system as a function of microstructure and energy offset.
The results could reproduce the main features of experimental electroluminescence
spectra indicating that electron–hole pairs become less bound
and more spatially separated upon increasing energy offset and fullerene
domain density. Differences between electroluminescence and photoluminescence
spectra could be explained by CT photoluminescence being dominated
by more-bound states, reflecting geminate recombination processes,
while CT electroluminescence preferentially probes less-bound CT states
that escape geminate recombination. These results suggest that apparently
contradictory studies on electron–hole separation can be explained
by the presence of both bound and unbound CT states in the same film,
as a result of a range of interface structures.
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Affiliation(s)
- S D Dimitrov
- SPECIFIC, College of Engineering , Swansea University , Bay Campus , Swansea SA1 8EN , United Kingdom
| | | | | | | | | | | | - B C Schroeder
- Department of Chemistry , University College , London WC1H 0AJ , United Kingdom
| | - E R Bittner
- Department of Chemistry , University of Houston , Houston , Texas 77204 , United States
| | - I McCulloch
- Physical Sciences and Engineering Division, KAUST Solar Center (KSC) , King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900 , Kingdom of Saudi Arabia
| | | | - J R Durrant
- SPECIFIC, College of Engineering , Swansea University , Bay Campus , Swansea SA1 8EN , United Kingdom
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14
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Kurpiers J, Ferron T, Roland S, Jakoby M, Thiede T, Jaiser F, Albrecht S, Janietz S, Collins BA, Howard IA, Neher D. Probing the pathways of free charge generation in organic bulk heterojunction solar cells. Nat Commun 2018; 9:2038. [PMID: 29795114 PMCID: PMC5966440 DOI: 10.1038/s41467-018-04386-3] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 04/24/2018] [Indexed: 11/30/2022] Open
Abstract
The fact that organic solar cells perform efficiently despite the low dielectric constant of most photoactive blends initiated a long-standing debate regarding the dominant pathways of free charge formation. Here, we address this issue through the accurate measurement of the activation energy for free charge photogeneration over a wide range of photon energy, using the method of time-delayed collection field. For our prototypical low bandgap polymer:fullerene blends, we find that neither the temperature nor the field dependence of free charge generation depend on the excitation energy, ruling out an appreciable contribution to free charge generation though hot carrier pathways. On the other hand, activation energies are on the order of the room temperature thermal energy for all studied blends. We conclude that charge generation in such devices proceeds through thermalized charge transfer states, and that thermal energy is sufficient to separate most of these states into free charges. Contradictory models are being debated on the dominant pathways of charge generation in organic solar cells. Here Kurpiers et al. determine the activation energy for this fundamental process and reveal that the main channel is via thermalized charge transfer states instead of hot exciton dissociation.
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Affiliation(s)
- Jona Kurpiers
- Institute of Physics and Astronomy, Soft Matter Physics, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Potsdam-Golm, Germany
| | - Thomas Ferron
- Department of Physics and Astronomy, Washington State University, 100 Dairy Road, Pullman, WA, 99164, USA
| | - Steffen Roland
- Institute of Physics and Astronomy, Soft Matter Physics, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Potsdam-Golm, Germany
| | - Marius Jakoby
- Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology (IMT), Hermann-von-Helmholtz Platz-1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Tobias Thiede
- Institute of Physics and Astronomy, Soft Matter Physics, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Potsdam-Golm, Germany
| | - Frank Jaiser
- Institute of Physics and Astronomy, Soft Matter Physics, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Potsdam-Golm, Germany
| | - Steve Albrecht
- Helmholtz-Zentrum Berlin für Materialien und Energie, Nachwuchsgruppe Perowskit Tandemsolarzellen, Kekuléstraße 5, 12489, Berlin, Germany
| | - Silvia Janietz
- Fraunhofer IAP, Polymere und Elektronik, Geiselbergstraße 69, 14476, Potsdam-Golm, Germany
| | - Brian A Collins
- Department of Physics and Astronomy, Washington State University, 100 Dairy Road, Pullman, WA, 99164, USA
| | - Ian A Howard
- Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology (IMT), Hermann-von-Helmholtz Platz-1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Dieter Neher
- Institute of Physics and Astronomy, Soft Matter Physics, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Potsdam-Golm, Germany.
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15
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Organic solar cells based on anthracene-containing PPE–PPVs and non-fullerene acceptors. CHEMICAL PAPERS 2018. [DOI: 10.1007/s11696-018-0466-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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16
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Chochos CL, Singh R, Gregoriou VG, Kim M, Katsouras A, Serpetzoglou E, Konidakis I, Stratakis E, Cho K, Avgeropoulos A. Enhancement of the Power-Conversion Efficiency of Organic Solar Cells via Unveiling an Appropriate Rational Design Strategy in Indacenodithiophene- alt-quinoxaline π-Conjugated Polymers. ACS APPLIED MATERIALS & INTERFACES 2018; 10:10236-10245. [PMID: 29508996 DOI: 10.1021/acsami.7b18381] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report on the photovoltaic parameters, photophysical properties, optoelectronic properties, self-assembly, and morphology variations in a series of high-performance donor-acceptor (D-A) π-conjugated polymers based on indacenodithiophene and quinoxaline moieties as a function of the number-average molecular weight ([Formula: see text]), the nature of aryl substituents, and the enlargement of the polymer backbone. One of the most important outcome is that from the three optimization approaches followed to tune the chemical structure toward enhanced photovoltaic performance in bulk heterojunction solar cell devices with the fullerene derivative [6,6]-phenyl-C71-butyric acid methyl ester as the electron acceptor, the choice of the aryl substituent is the most efficient rational design strategy. Incorporation of thienyl rings as substituents versus phenyl rings accelerates the electron-hole extraction process to the respective electrode, despite the slightly lower recombination lifetime and, thus, improves the electrical performance of the device. Single-junction solar cells based on ThIDT-TQxT feature a maximum power-conversion efficiency of 7.26%. This study provides significant insights toward understanding of the structure-properties-performance relationship for D-A π-conjugated polymers in solid state, which provide helpful inputs for the design of next-generation polymeric semiconductors for organic solar cells with enhanced performance.
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Affiliation(s)
- Christos L Chochos
- Department of Materials Science Engineering , University of Ioannina , Ioannina 45110 , Greece
- Advent Technologies SA , Patras Science Park, Stadiou Street , Platani-Rio, 26504 Patras , Greece
| | - Ranbir Singh
- Department of Chemical Engineering , Pohang University of Science and Technology , Pohang 790-784 , Korea
| | - Vasilis G Gregoriou
- Advent Technologies SA , Patras Science Park, Stadiou Street , Platani-Rio, 26504 Patras , Greece
- National Hellenic Research Foundation (NHRF) , 48 Vassileos Constantinou Avenue , Athens 11635 , Greece
| | - Min Kim
- Department of Chemical Engineering , Pohang University of Science and Technology , Pohang 790-784 , Korea
| | - Athanasios Katsouras
- Department of Materials Science Engineering , University of Ioannina , Ioannina 45110 , Greece
| | - Efthymis Serpetzoglou
- Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas , P.O. Box 1527, Heraklion 71110 , Crete , Greece
| | - Ioannis Konidakis
- Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas , P.O. Box 1527, Heraklion 71110 , Crete , Greece
| | - Emmanuel Stratakis
- Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas , P.O. Box 1527, Heraklion 71110 , Crete , Greece
| | - Kilwon Cho
- Department of Chemical Engineering , Pohang University of Science and Technology , Pohang 790-784 , Korea
| | - Apostolos Avgeropoulos
- Department of Materials Science Engineering , University of Ioannina , Ioannina 45110 , Greece
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17
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Thermally Stable Bulk Heterojunction Prepared by Sequential Deposition of Nanostructured Polymer and Fullerene. Polymers (Basel) 2017; 9:polym9090456. [PMID: 30965759 PMCID: PMC6418660 DOI: 10.3390/polym9090456] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 09/07/2017] [Accepted: 09/12/2017] [Indexed: 11/16/2022] Open
Abstract
A morphologically-stable polymer/fullerene heterojunction has been prepared by minimizing the intermixing between polymer and fullerene via sequential deposition (SqD) of a polymer and a fullerene solution. A low crystalline conjugated polymer of PCPDTBT (poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]) has been utilized for the polymer layer and PC71BM (phenyl-C71-butyric-acid-methyl ester) for the fullerene layer, respectively. Firstly, a nanostructured PCPDTBT bottom layer was developed by utilizing various additives to increase the surface area of the polymer film. The PC71BM solution was prepared by dissolving it in the 1,2-dichloroethane (DCE), exhibiting a lower vapor pressure and slower diffusion into the polymer layer. The deposition of the PC71BM solution on the nanostructured PCPDTBT layer forms an inter-digitated bulk heterojunction (ID-BHJ) with minimized intermixing. The organic photovoltaic (OPV) device utilizing the ID-BHJ photoactive layer exhibits a highly reproducible solar cell performance. In spite of restricted intermixing between the PC71BM and the PCPDTBT, the efficiency of ID-BHJ OPVs (3.36%) is comparable to that of OPVs (3.87%) prepared by the conventional method (deposition of a blended solution of polymer:fullerene). The thermal stability of the ID-BHJ is superior to the bulk heterojunction (BHJ) prepared by the conventional method. The ID-BHJ OPV maintains 70% of its initial efficiency after thermal stress application for twelve days at 80 °C, whereas the conventional BHJ OPV maintains only 40% of its initial efficiency.
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18
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Impact of interfacial molecular orientation on radiative recombination and charge generation efficiency. Nat Commun 2017; 8:79. [PMID: 28724989 PMCID: PMC5517510 DOI: 10.1038/s41467-017-00107-4] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 05/31/2017] [Indexed: 12/03/2022] Open
Abstract
A long standing question in organic electronics concerns the effects of molecular orientation at donor/acceptor heterojunctions. Given a well-controlled donor/acceptor bilayer system, we uncover the genuine effects of molecular orientation on charge generation and recombination. These effects are studied through the point of view of photovoltaics—however, the results have important implications on the operation of all optoelectronic devices with donor/acceptor interfaces, such as light emitting diodes and photodetectors. Our findings can be summarized by two points. First, devices with donor molecules face-on to the acceptor interface have a higher charge transfer state energy and less non-radiative recombination, resulting in larger open-circuit voltages and higher radiative efficiencies. Second, devices with donor molecules edge-on to the acceptor interface are more efficient at charge generation, attributed to smaller electronic coupling between the charge transfer states and the ground state, and lower activation energy for charge generation. Molecular orientation profoundly affects the performance of donor-acceptor heterojunctions, whilst it has remained challenging to investigate the detail. Using a controllable interface, Ran et al. show that the edge-on geometries improve charge generation at the cost of non-radiative recombination loss.
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19
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Zhang Y, Yuan J, Sun J, Ding G, Han L, Ling X, Ma W. Alkenyl Carboxylic Acid: Engineering the Nanomorphology in Polymer-Polymer Solar Cells as Solvent Additive. ACS APPLIED MATERIALS & INTERFACES 2017; 9:13396-13405. [PMID: 28368094 DOI: 10.1021/acsami.7b02075] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We have investigated a series of commercially available alkenyl carboxylic acids with different alkenyl chain lengths (trans-2-hexenoic acid (CA-6), trans-2-decenoic acid (CA-10), 9-tetradecenoic acid (CA-14)) for use as solvent additives in polymer-polymer non-fullerene solar cells. We systematically investigated their effect on the film absorption, morphology, carrier generation, transport, and recombination in all-polymer solar cells. We revealed that these additives have a significant impact on the aggregation of polymer acceptor, leading to improved phase segregation in the blend film. This in-depth understanding of the additives effect on the nanomorphology in all-polymer solar cell can help further boost the device performance. By using CA-10 with the optimal alkenyl chain length, we achieved fine phase separation, balanced charge transport, and suppressed recombination in all-polymer solar cells. As a result, an optimal power conversion efficiency (PCE) of 5.71% was demonstrated which is over 50% higher than that of the as-cast device (PCE = 3.71%) and slightly higher than that of devices with DIO treatment (PCE = 5.68%). Compared with widely used DIO, these halogen-free alkenyl carboxylic acids have a more sustainable processing as well as better performance, which may make them more promising candidates for use as processing additives in organic non-fullerene solar cells.
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Affiliation(s)
- Yannan Zhang
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou, Jiangsu, P. R. China
| | - Jianyu Yuan
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou, Jiangsu, P. R. China
| | - Jianxia Sun
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou, Jiangsu, P. R. China
| | - Guanqun Ding
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou, Jiangsu, P. R. China
| | - Lu Han
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou, Jiangsu, P. R. China
| | - Xufeng Ling
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou, Jiangsu, P. R. China
| | - Wanli Ma
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou, Jiangsu, P. R. China
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20
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Charge Carrier Generation, Recombination, and Extraction in Polymer–Fullerene Bulk Heterojunction Organic Solar Cells. ELEMENTARY PROCESSES IN ORGANIC PHOTOVOLTAICS 2017. [DOI: 10.1007/978-3-319-28338-8_11] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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21
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Fernández Garrillo PA, Borowik Ł, Caffy F, Demadrille R, Grévin B. Photo-Carrier Multi-Dynamical Imaging at the Nanometer Scale in Organic and Inorganic Solar Cells. ACS APPLIED MATERIALS & INTERFACES 2016; 8:31460-31468. [PMID: 27762134 DOI: 10.1021/acsami.6b11423] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Investigating the photocarrier dynamics in nanostructured and heterogeneous energy materials is of crucial importance from both fundamental and technological points of view. Here, we demonstrate how noncontact atomic force microscopy combined with Kelvin probe force microscopy under frequency-modulated illumination can be used to simultaneously image the surface photopotential dynamics at different time scales with a sub-10 nm lateral resolution. The basic principle of the method consists in the acquisition of spectroscopic curves of the surface potential as a function of the illumination frequency modulation on a two-dimensional grid. We show how this frequency-spectroscopy can be used to probe simultaneously the charging rate and several decay processes involving short-lived and long-lived carriers. With this approach, dynamical images of the trap-filling, trap-delayed recombination and nongeminate recombination processes have been acquired in nanophase segregated organic donor-acceptor bulk heterojunction thin films. Furthermore, the spatial variation of the minority carrier lifetime has been imaged in polycrystalline silicon thin films. These results establish two-dimensional multidynamical photovoltage imaging as a universal tool for local investigations of the photocarrier dynamics in photoactive materials and devices.
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Affiliation(s)
- Pablo A Fernández Garrillo
- Université Grenoble Alpes , F-38000 Grenoble, France
- CEA , LETI, MINATEC Campus, F-38054 Grenoble, France
- INAC-SPrAM, CEA, CNRS, Université Grenoble Alpes , F-38000 Grenoble, France
| | - Łukasz Borowik
- Université Grenoble Alpes , F-38000 Grenoble, France
- CEA , LETI, MINATEC Campus, F-38054 Grenoble, France
| | - Florent Caffy
- INAC-SPrAM, CEA, CNRS, Université Grenoble Alpes , F-38000 Grenoble, France
| | - Renaud Demadrille
- INAC-SPrAM, CEA, CNRS, Université Grenoble Alpes , F-38000 Grenoble, France
| | - Benjamin Grévin
- INAC-SPrAM, CEA, CNRS, Université Grenoble Alpes , F-38000 Grenoble, France
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22
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van den Berg M, Back J, Horneber A, Meixner M, Swider K, Ludwigs S, Zhang D. Determination of the Local Morphology within Individual Polymer Domains. Macromolecules 2016. [DOI: 10.1021/acs.macromol.6b01671] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Marius van den Berg
- Institute
for Physical and Theoretical Chemistry, Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Justus Back
- Institute
of Polymer Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Anke Horneber
- Institute
for Physical and Theoretical Chemistry, Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Martin Meixner
- Institute
for Physical and Theoretical Chemistry, Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Kathrin Swider
- Institute
for Physical and Theoretical Chemistry, Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Sabine Ludwigs
- Institute
of Polymer Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Dai Zhang
- Institute
for Physical and Theoretical Chemistry, Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
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23
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Lee D, Kim JK, Jang DJ. Excited-state dynamics of an amphiphilic diblock copolymer self-assembled from mixed solvents. POLYMER 2016. [DOI: 10.1016/j.polymer.2016.07.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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24
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Kurpiers J, Neher D. Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend. Sci Rep 2016; 6:26832. [PMID: 27225584 PMCID: PMC4881019 DOI: 10.1038/srep26832] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 05/10/2016] [Indexed: 11/16/2022] Open
Abstract
Recombination of free charge is a key process limiting the performance of solar cells. For low mobility materials, such as organic semiconductors, the kinetics of non-geminate recombination (NGR) is strongly linked to the motion of charges. As these materials possess significant disorder, thermalization of photogenerated carriers in the inhomogeneously broadened density of state distribution is an unavoidable process. Despite its general importance, knowledge about the kinetics of NGR in complete organic solar cells is rather limited. We employ time delayed collection field (TDCF) experiments to study the recombination of photogenerated charge in the high-performance polymer:fullerene blend PCDTBT:PCBM. NGR in the bulk of this amorphous blend is shown to be highly dispersive, with a continuous reduction of the recombination coefficient throughout the entire time scale, until all charge carriers have either been extracted or recombined. Rapid, contact-mediated recombination is identified as an additional loss channel, which, if not properly taken into account, would erroneously suggest a pronounced field dependence of charge generation. These findings are in stark contrast to the results of TDCF experiments on photovoltaic devices made from ordered blends, such as P3HT:PCBM, where non-dispersive recombination was proven to dominate the charge carrier dynamics under application relevant conditions.
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Affiliation(s)
- Jona Kurpiers
- Institute of Physics and Astronomy, Soft Matter Physics, University of Potsdam, D-14476 Potsdam, Germany
| | - Dieter Neher
- Institute of Physics and Astronomy, Soft Matter Physics, University of Potsdam, D-14476 Potsdam, Germany
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25
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Pranculis V, Ruseckas A, Vithanage D, Hedley GJ, Samuel IDW, Gulbinas V. Influence of Blend Ratio and Processing Additive on Free Carrier Yield and Mobility in PTB7:PC 71BM Photovoltaic Solar Cells. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2016; 120:9588-9594. [PMID: 27293495 PMCID: PMC4897731 DOI: 10.1021/acs.jpcc.6b01548] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 04/21/2016] [Indexed: 06/06/2023]
Abstract
Charge separation and extraction dynamics were investigated in high-performance bulk heterojunction solar cells made from the polymer PTB7 and the soluble fullerene PC71BM on a broad time scale from subpicosecond to microseconds using ultrafast optical probing of carrier drift and the integral-mode photocurrent measurements. We show that the short circuit current is determined by the separation of charge pairs into free carriers, which is strongly influenced by blend composition. This separation is found to be efficient in fullerene-rich blends where a high electron mobility of >0.1 cm2 V-1 s-1 is observed in the first 10 ps after excitation. Morphology optimization using the solvent additive 1,8-diiodooctane (DIO) doubles the charge pair separation efficiency and the short-circuit current. Carrier extraction at low internal electric field is slightly faster from the cells prepared with DIO, which can reduce recombination losses and enhance a fill factor.
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Affiliation(s)
- Vytenis Pranculis
- Center
for Physical Sciences and Technology, Savanoriu Ave 231, 02300 Vilnius, Lithuania
| | - Arvydas Ruseckas
- Organic
Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - Dimali
A. Vithanage
- Organic
Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - Gordon J. Hedley
- Organic
Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - Ifor D. W. Samuel
- Organic
Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - Vidmantas Gulbinas
- Center
for Physical Sciences and Technology, Savanoriu Ave 231, 02300 Vilnius, Lithuania
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26
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Neher D, Kniepert J, Elimelech A, Koster LJA. A New Figure of Merit for Organic Solar Cells with Transport-limited Photocurrents. Sci Rep 2016; 6:24861. [PMID: 27112905 PMCID: PMC4845057 DOI: 10.1038/srep24861] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 04/06/2016] [Indexed: 11/29/2022] Open
Abstract
Compared to their inorganic counterparts, organic semiconductors suffer from relatively low charge carrier mobilities. Therefore, expressions derived for inorganic solar cells to correlate characteristic performance parameters to material properties are prone to fail when applied to organic devices. This is especially true for the classical Shockley-equation commonly used to describe current-voltage (JV)-curves, as it assumes a high electrical conductivity of the charge transporting material. Here, an analytical expression for the JV-curves of organic solar cells is derived based on a previously published analytical model. This expression, bearing a similar functional dependence as the Shockley-equation, delivers a new figure of merit α to express the balance between free charge recombination and extraction in low mobility photoactive materials. This figure of merit is shown to determine critical device parameters such as the apparent series resistance and the fill factor.
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Affiliation(s)
- Dieter Neher
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str.24-25, D-14476 Potsdam-Golm, Germany
| | - Juliane Kniepert
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str.24-25, D-14476 Potsdam-Golm, Germany
| | - Arik Elimelech
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str.24-25, D-14476 Potsdam-Golm, Germany
| | - L Jan Anton Koster
- Photophysics and Optoelectronics, Zernike Institute for Advanced Materials, Nijenborgh 4, NL-9747AG Groningen, The Netherlands
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27
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Zhang F, Inganäs O, Zhou Y, Vandewal K. Development of polymer–fullerene solar cells. Natl Sci Rev 2016. [DOI: 10.1093/nsr/nww020] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Global efforts and synergetic interdisciplinary collaborations on solution-processed bulk-heterojunction polymer solar cells (PSCs or OPVs) made power conversion efficiencies over 10% possible. The rapid progress of the field is credited to the synthesis of a large number of novel polymers with specially tunable optoelectronic properties, a better control over the nano-morphology of photoactive blend layers, the introduction of various effective interfacial layers, new device architectures and a deeper understanding of device physics. We will review the pioneering materials for polymer–fullerene solar cells and trace the progress of concepts driving their development. We discuss the evolution of morphology control, interfacial layers and device structures fully exploring the potential of photoactive materials. In order to guide a further increase in power conversion efficiency of OPV, the current understanding of the process of free charge carrier generation and the origin of the photovoltage is summarized followed by a perspective on how to overcome the limitations for industrializing PSCs.
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Affiliation(s)
- Fengling Zhang
- Biomolecular and organic electronics, Department of Physics, Chemistry and Biology (IFM), Linkoping University, 58183 Linkoping, Sweden
| | - Olle Inganäs
- Biomolecular and organic electronics, Department of Physics, Chemistry and Biology (IFM), Linkoping University, 58183 Linkoping, Sweden
| | - Yinhua Zhou
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Koen Vandewal
- Institut für Angewandte Photophysik, Technische Universität Dresden, 01069 Dresden, Germany
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28
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van der Kaap NJ, Koster LJA. Charge carrier thermalization in organic diodes. Sci Rep 2016; 6:19794. [PMID: 26791095 PMCID: PMC4726152 DOI: 10.1038/srep19794] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 12/18/2015] [Indexed: 11/09/2022] Open
Abstract
Charge carrier mobilities of organic semiconductors are often characterized using steady-state measurements of space charge limited diodes. These measurements assume that charge carriers are in a steady-state equilibrium. In reality, however, energetically hot carriers are introduces by photo-excitation and injection into highly energetic sites from the electrodes. These carriers perturb the equilibrium density of occupied states, and therefore change the overall charge transport properties. In this paper, we look into the effect of energetically hot carriers on the charge transport in organic semiconductors using steady state kinetic Monte Carlo simulations. For injected hot carriers in a typical organic semiconductor, rapid energetic relaxation occurs in the order of tens of nanoseconds, which is much faster than the typical transit time of a charge carrier throught the device. Furthermore, we investigate the impact of photo-generated carriers on the steady-state mobility. For a typical organic voltaic material, an increase in mobility of a factor of 1.1 is found. Therefore, we conclude that the impact of energetically hot carriers on normal device operation is limited.
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Affiliation(s)
- N J van der Kaap
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - L J A Koster
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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29
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Cappel UB, Plogmaker S, Terschlüsen JA, Leitner T, Johansson EMJ, Edvinsson T, Sandell A, Karis O, Siegbahn H, Svensson S, Mårtensson N, Rensmo H, Söderström J. Electronic structure dynamics in a low bandgap polymer studied by time-resolved photoelectron spectroscopy. Phys Chem Chem Phys 2016; 18:21921-9. [DOI: 10.1039/c6cp04136a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The excited electronic structure of PCPDTBT was measured by combining a high harmonic generation source and a time-of-flight spectrometer.
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30
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Du C, Ji Y, Xue J, Hou T, Tang J, Lee ST, Li Y. Morphology and Performance of Polymer Solar Cell Characterized by DPD Simulation and Graph Theory. Sci Rep 2015; 5:16854. [PMID: 26581407 PMCID: PMC4652231 DOI: 10.1038/srep16854] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 10/21/2015] [Indexed: 12/30/2022] Open
Abstract
The morphology of active layers in the bulk heterojunction (BHJ) solar cells is critical to the performance of organic photovoltaics (OPV). Currently, there is limited information for the morphology from transmission electron microscopy (TEM) techniques. Meanwhile, there are limited approaches to predict the morphology /efficiency of OPV. Here we use Dissipative Particle Dynamics (DPD) to determine 3D morphology of BHJ solar cells and show DPD to be an efficient approach to predict the 3D morphology. Based on the 3D morphology, we estimate the performance indicator of BHJ solar cells by using graph theory. Specifically, we study poly (3-hexylthiophene)/[6, 6]-phenyl-C61butyric acid methyl ester (P3HT/PCBM) BHJ solar cells. We find that, when the volume fraction of PCBM is in the region 0.4 ∼ 0.5, P3HT/PCBM will show bi-continuous morphology and optimum performance, consistent with experimental results. Further, the optimum temperature (413 K) for the morphology and performance of P3HT/PCBM is in accord with annealing results. We find that solvent additive plays a critical role in the desolvation process of P3HT/PCBM BHJ solar cell. Our approach provides a direct method to predict dynamic 3D morphology and performance indicator for BHJ solar cells.
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Affiliation(s)
- Chunmiao Du
- Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, P.R. China
| | - Yujin Ji
- Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, P.R. China
| | - Junwei Xue
- Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, P.R. China
| | - Tingjun Hou
- Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, P.R. China
| | - Jianxin Tang
- Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, P.R. China
| | - Shuit-Tong Lee
- Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, P.R. China
| | - Youyong Li
- Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, P.R. China
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31
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Lin JDA, Mikhnenko OV, van der Poll TS, Bazan GC, Nguyen TQ. Temperature dependence of exciton diffusion in a small-molecule organic semiconductor processed with and without additive. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:2528-32. [PMID: 25775936 DOI: 10.1002/adma.201404590] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2014] [Revised: 02/09/2015] [Indexed: 05/23/2023]
Abstract
The temperature dependence of exciton diffusion in a small-molecule organic semiconductor processed with and without additive is investigated. As-cast and 1,8-diiodooctane-processed films yield exciton diffusion lengths of 6.8 and 4.9 nm, respectively. Using a Monte Carlo simulation, it is shown that processing with 1,8-diiodooctane increases the excitonic trap density, which directly reduces the exciton diffusion length.
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Affiliation(s)
- Jason D A Lin
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, 93106, USA
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32
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Fischer FSU, Trefz D, Back J, Kayunkid N, Tornow B, Albrecht S, Yager KG, Singh G, Karim A, Neher D, Brinkmann M, Ludwigs S. Highly crystalline films of PCPDTBT with branched side chains by solvent vapor crystallization: influence on opto-electronic properties. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:1223-1228. [PMID: 25482608 DOI: 10.1002/adma.201403475] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 09/19/2014] [Indexed: 06/04/2023]
Abstract
PCPDTBT, a marginally crystallizable polymer, is crystallized into a new crystal structure using solvent-vapor annealing. Highly ordered areas with three different polymer-chain orientations are identified using TEM/ED, GIWAXS, and polarized Raman spectroscopy. The optical and structural properties differ significantly from films prepared by standard device preparation protocols. Bilayer solar cells, however, show similar performance.
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Affiliation(s)
- Florian S U Fischer
- IPOC-Functional Polymers, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
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33
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Zusan A, Gieseking B, Zerson M, Dyakonov V, Magerle R, Deibel C. The effect of diiodooctane on the charge carrier generation in organic solar cells based on the copolymer PBDTTT-C. Sci Rep 2015; 5:8286. [PMID: 25655785 PMCID: PMC4319164 DOI: 10.1038/srep08286] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 01/13/2015] [Indexed: 11/18/2022] Open
Abstract
Microstructural changes and the understanding of their effect on photocurrent generation are key aspects for improving the efficiency of organic photovoltaic devices. We analyze the impact of a systematically increased amount of the solvent additive diiodooctane (DIO) on the morphology of PBDTTT-C:PC71BM blends and related changes in free carrier formation and recombination by combining surface imaging, photophysical and charge extraction techniques. We identify agglomerates visible in AFM images of the 0% DIO blend as PC71BM domains embedded in an intermixed matrix phase. With the addition of DIO, a decrease in the size of fullerene domains along with a demixing of the matrix phase appears for 0.6% and 1% DIO. Surprisingly, transient absorption spectroscopy reveals an efficient photogeneration already for the smallest amount of DIO, although the largest efficiency is found for 3% DIO. It is ascribed to a fine-tuning of the blend morphology in terms of the formation of interpenetrating donor and acceptor phases minimizing geminate and nongeminate recombination as indicated by charge extraction experiments. An increase in the DIO content to 10% adversely affects the photovoltaic performance, most probably due to an inefficient free carrier formation and trapping in a less interconnected donor-acceptor network.
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Affiliation(s)
- Andreas Zusan
- Experimental Physics VI, Julius-Maximilians-University of Würzburg, 97074 Würzburg, Germany
| | - Björn Gieseking
- Experimental Physics VI, Julius-Maximilians-University of Würzburg, 97074 Würzburg, Germany
| | - Mario Zerson
- Fakultät für Naturwissenschaften, Technische Universität Chemnitz, 09126 Chemnitz, Germany
| | - Vladimir Dyakonov
- 1] Experimental Physics VI, Julius-Maximilians-University of Würzburg, 97074 Würzburg, Germany [2] Bavarian Center for Applied Energy Research e.V. (ZAE Bayern), 97074 Würzburg, Germany
| | - Robert Magerle
- Fakultät für Naturwissenschaften, Technische Universität Chemnitz, 09126 Chemnitz, Germany
| | - Carsten Deibel
- Experimental Physics VI, Julius-Maximilians-University of Würzburg, 97074 Würzburg, Germany
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34
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Mukherjee S, Proctor CM, Tumbleston JR, Bazan GC, Nguyen TQ, Ade H. Importance of domain purity and molecular packing in efficient solution-processed small-molecule solar cells. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:1105-1111. [PMID: 25530459 DOI: 10.1002/adma.201404388] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Indexed: 06/04/2023]
Abstract
Connections are delineated between solar-cell performance, charge-carrier mobilities, and morphology in a highperformance molecular solar cell. The observations show that maximizing the relative phase purity and structural order while simultaneously limiting the domain size may be essential for achieving optimal solar-cell performances in solution-processed small-molecule solar cells .
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Affiliation(s)
- Subhrangsu Mukherjee
- Department of Physics, North Carolina State University, Raleigh, North Carolina, 27695, USA
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35
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Few S, Frost JM, Nelson J. Models of charge pair generation in organic solar cells. Phys Chem Chem Phys 2015; 17:2311-2325. [DOI: 10.1039/c4cp03663h] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A critical perspective on modelling of charge generation in organic photovoltaics, focussing on interfacial electronic states, electrostatics, and dynamic processes.
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Affiliation(s)
- Sheridan Few
- Centre for Plastic Electronics
- Department of Physics
- Imperial College London
- London SW7 2AZ
- UK
| | - Jarvist M. Frost
- Centre for Plastic Electronics
- Department of Physics
- Imperial College London
- London SW7 2AZ
- UK
| | - Jenny Nelson
- Centre for Plastic Electronics
- Department of Physics
- Imperial College London
- London SW7 2AZ
- UK
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36
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Li W, Albrecht S, Yang L, Roland S, Tumbleston JR, McAfee T, Yan L, Kelly MA, Ade H, Neher D, You W. Mobility-Controlled Performance of Thick Solar Cells Based on Fluorinated Copolymers. J Am Chem Soc 2014; 136:15566-76. [DOI: 10.1021/ja5067724] [Citation(s) in RCA: 237] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Wentao Li
- Department
of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Steve Albrecht
- Institute
of Physics and Astronomy, Soft Matter Physics, University of Potsdam, 14476 Potsdam, Germany
| | - Liqiang Yang
- Department
of Applied Physical Sciences, CB #3216, University of North Carolina, Chapel Hill, North Carolina 27599-3216, United States
| | - Steffen Roland
- Institute
of Physics and Astronomy, Soft Matter Physics, University of Potsdam, 14476 Potsdam, Germany
| | - John R. Tumbleston
- Department
of Physics, North Carolina State University, Raleigh, North Carolina 27615, United States
| | - Terry McAfee
- Department
of Physics, North Carolina State University, Raleigh, North Carolina 27615, United States
| | - Liang Yan
- Department
of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Mary Allison Kelly
- Department
of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Harald Ade
- Department
of Physics, North Carolina State University, Raleigh, North Carolina 27615, United States
| | - Dieter Neher
- Institute
of Physics and Astronomy, Soft Matter Physics, University of Potsdam, 14476 Potsdam, Germany
| | - Wei You
- Department
of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
- Department
of Applied Physical Sciences, CB #3216, University of North Carolina, Chapel Hill, North Carolina 27599-3216, United States
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37
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38
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Roland S, Schubert M, Collins BA, Kurpiers J, Chen Z, Facchetti A, Ade H, Neher D. Fullerene-Free Polymer Solar Cells with Highly Reduced Bimolecular Recombination and Field-Independent Charge Carrier Generation. J Phys Chem Lett 2014; 5:2815-2822. [PMID: 26278084 DOI: 10.1021/jz501506z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Photogeneration, recombination, and transport of free charge carriers in all-polymer bulk heterojunction solar cells incorporating poly(3-hexylthiophene) (P3HT) as donor and poly([N,N'-bis(2-octyldodecyl)-naphthelene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)) (P(NDI2OD-T2)) as acceptor polymer have been investigated by the use of time delayed collection field (TDCF) and time-of-flight (TOF) measurements. Depending on the preparation procedure used to dry the active layers, these solar cells comprise high fill factors (FFs) of up to 67%. A strongly reduced bimolecular recombination (BMR), as well as a field-independent free charge carrier generation are observed, features that are common to high performance fullerene-based solar cells. Resonant soft X-ray measurements (R-SoXS) and photoluminescence quenching experiments (PQE) reveal that the BMR is related to domain purity. Our results elucidate the similarities of this polymeric acceptor with the superior recombination properties of fullerene acceptors.
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Affiliation(s)
- Steffen Roland
- †Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany
| | - Marcel Schubert
- †Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany
| | - Brian A Collins
- ‡Department of Physics, North Carolina State University, Raleigh, North Carolina 27695, United States
- §National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, United States
| | - Jona Kurpiers
- †Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany
| | - Zhihua Chen
- ∥Polyera Corporation, Skokie, Illinois 60077, United States
| | | | - Harald Ade
- ‡Department of Physics, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Dieter Neher
- †Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany
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39
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Gao F, Inganäs O. Charge generation in polymer-fullerene bulk-heterojunction solar cells. Phys Chem Chem Phys 2014; 16:20291-304. [PMID: 24994122 DOI: 10.1039/c4cp01814a] [Citation(s) in RCA: 169] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Charge generation in organic solar cells is a fundamental yet heavily debated issue. This article gives a balanced review of different mechanisms proposed to explain efficient charge generation in polymer-fullerene bulk-heterojunction solar cells. We discuss the effect of charge-transfer states, excess energy, external electric field, temperature, disorder of the materials, and delocalisation of the charge carriers on charge generation. Although a general consensus has not been reached yet, recent findings, based on both steady-state and transient measurements, have significantly advanced our understanding of this process.
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Affiliation(s)
- Feng Gao
- Biomolecular and Organic Electronics, IFM and Center of Organic Electronics, Linköping University, Linköping SE-581 83, Sweden.
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40
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Ma W, Tumbleston JR, Ye L, Wang C, Hou J, Ade H. Quantification of nano- and mesoscale phase separation and relation to donor and acceptor quantum efficiency, J(sc), and FF in polymer:fullerene solar cells. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:4234-41. [PMID: 24677439 DOI: 10.1002/adma.201400216] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 02/09/2014] [Indexed: 05/12/2023]
Affiliation(s)
- Wei Ma
- Department of Physics, North Carolina State University, Raleigh, NC, 27695, USA
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41
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Albrecht S, Tumbleston JR, Janietz S, Dumsch I, Allard S, Scherf U, Ade H, Neher D. Quantifying Charge Extraction in Organic Solar Cells: The Case of Fluorinated PCPDTBT. J Phys Chem Lett 2014; 5:1131-1138. [PMID: 26274460 DOI: 10.1021/jz500457b] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We introduce a new and simple method to quantify the effective extraction mobility in organic solar cells at low electric fields and charge carrier densities comparable to operation conditions under one sun illumination. By comparing steady-state carrier densities at constant illumination intensity and under open-circuit conditions, the gradient of the quasi-Fermi potential driving the current is estimated as a function of external bias and charge density. These properties are then related to the respective steady-state current to determine the effective extraction mobility. The new technique is applied to different derivatives of the well-known low-band-gap polymer PCPDTBT blended with PC70BM. We show that the slower average extraction due to lower mobility accounts for the moderate fill factor when solar cells are fabricated with mono- or difluorinated PCPDTBT. This lower extraction competes with improved generation and reduced nongeminate recombination, rendering the monofluorinated derivative the most efficient donor polymer.
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Affiliation(s)
- Steve Albrecht
- †Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - John R Tumbleston
- ‡Department of Physics, North Carolina State University, 421 Riddick Hall, Raleigh, North Carolina 27695-8202, United States
| | - Silvia Janietz
- §Fraunhofer Institut für Angewandte Polymerforschung, Geiselbergstr. 69, 14476 Potsdam, Germany
| | - Ines Dumsch
- ∥Bergische Universität Wuppertal, Institut für Polymertechnologie, Gauss-Str. 20, 42097 Wuppertal, Germany
| | - Sybille Allard
- ∥Bergische Universität Wuppertal, Institut für Polymertechnologie, Gauss-Str. 20, 42097 Wuppertal, Germany
| | - Ullrich Scherf
- ∥Bergische Universität Wuppertal, Institut für Polymertechnologie, Gauss-Str. 20, 42097 Wuppertal, Germany
| | - Harald Ade
- ‡Department of Physics, North Carolina State University, 421 Riddick Hall, Raleigh, North Carolina 27695-8202, United States
| | - Dieter Neher
- †Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
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42
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Affiliation(s)
- Girish Lakhwani
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom;
| | - Akshay Rao
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom;
| | - Richard H. Friend
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom;
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43
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Lin JDA, Liu J, Kim C, Tamayo AB, Proctor CM, Nguyen TQ. Effect of structural variation on photovoltaic characteristics of phenyl substituted diketopyrrolopyrroles. RSC Adv 2014. [DOI: 10.1039/c3ra45662e] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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44
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Venkatesan S, Adhikari N, Chen J, Ngo EC, Dubey A, Galipeau DW, Qiao Q. Interplay of nanoscale domain purity and size on charge transport and recombination dynamics in polymer solar cells. NANOSCALE 2014; 6:1011-1019. [PMID: 24292406 DOI: 10.1039/c3nr05177c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Charge transport and bimolecular recombination dynamics were correlated with nanomorphology in polymer solar cells. The morphology of poly(diketopyrrolopyrrole-terthiophene) (PDPP3T) and phenyl-C61-butyric acid methyl ester (PC60BM) blend films was modified using different solvent additives namely 1-chloronaphthalene (CN), 1,8-diiodooctane (DIO) and 1,8-octanedithiol (ODT) and their role on steady state and transient optoelectronic properties was investigated. The energy filtered transmission electron microscopy (EFTEM) images showed that additives (e.g. CN and DIO) improved the domain purity which leads to significantly higher short circuit current densities (Jsc). However when the cells were processed with the ODT additive, the fill factor (FF) and open circuit voltage (Voc) decreased dramatically. Films processed with the ODT additive showed a smaller domain size but were more connected compared to films processed using CN and DIO additives. Transient photocurrent analysis indicates faster charge collection in the case of CN and DIO processed solar cells and the slowest charge collection in ODT processed solar cells. Interestingly devices processed with the ODT additive also showed the longest charge carrier recombination lifetime and lowest bimolecular recombination coefficient. This is attributed to the smaller donor domains that are connected with each other to provide a more interconnected and efficient charge transport matrix but longer pathways in ODT films. Such a matrix helped the charge to escape from the donor-acceptor interfaces and thus reduces the bimolecular recombination, while the longer pathway increases the charge collection time. Further insight is provided into the selection of processing conditions to achieve an ideal active layer morphology consisting of domains with higher polymer purity and optimal size that lead to higher Jsc and FF.
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Affiliation(s)
- Swaminathan Venkatesan
- Department of Electrical Engineering, Center for Advanced Photovoltaics, South Dakota State University, Brookings, SD, USA.
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Vandewal K, Albrecht S, Hoke ET, Graham KR, Widmer J, Douglas JD, Schubert M, Mateker WR, Bloking JT, Burkhard GF, Sellinger A, Fréchet JMJ, Amassian A, Riede MK, McGehee MD, Neher D, Salleo A. Efficient charge generation by relaxed charge-transfer states at organic interfaces. NATURE MATERIALS 2014; 13:63-8. [PMID: 24240240 DOI: 10.1038/nmat3807] [Citation(s) in RCA: 189] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 10/08/2013] [Indexed: 05/20/2023]
Abstract
Interfaces between organic electron-donating (D) and electron-accepting (A) materials have the ability to generate charge carriers on illumination. Efficient organic solar cells require a high yield for this process, combined with a minimum of energy losses. Here, we investigate the role of the lowest energy emissive interfacial charge-transfer state (CT1) in the charge generation process. We measure the quantum yield and the electric field dependence of charge generation on excitation of the charge-transfer (CT) state manifold via weakly allowed, low-energy optical transitions. For a wide range of photovoltaic devices based on polymer:fullerene, small-molecule:C60 and polymer:polymer blends, our study reveals that the internal quantum efficiency (IQE) is essentially independent of whether or not D, A or CT states with an energy higher than that of CT1 are excited. The best materials systems show an IQE higher than 90% without the need for excess electronic or vibrational energy.
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Affiliation(s)
- Koen Vandewal
- Department of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA
| | - Steve Albrecht
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany
| | - Eric T Hoke
- Department of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA
| | - Kenneth R Graham
- 1] Department of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA [2] King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Johannes Widmer
- Institut für Angewandte Photophysik TU Dresden, George-Bähr-Strasse 1, 01062, Dresden, Germany
| | - Jessica D Douglas
- Department of Chemistry, University of California, 727 Latimer Hall, Berkeley, California 94720, USA
| | - Marcel Schubert
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany
| | - William R Mateker
- Department of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA
| | - Jason T Bloking
- Department of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA
| | - George F Burkhard
- Department of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA
| | - Alan Sellinger
- 1] Department of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA [2]
| | - Jean M J Fréchet
- 1] King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia [2] Department of Chemistry, University of California, 727 Latimer Hall, Berkeley, California 94720, USA
| | - Aram Amassian
- King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Moritz K Riede
- 1] Institut für Angewandte Photophysik TU Dresden, George-Bähr-Strasse 1, 01062, Dresden, Germany [2]
| | - Michael D McGehee
- Department of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA
| | - Dieter Neher
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany
| | - Alberto Salleo
- Department of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA
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47
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Deng Z, Chen L, Chen Y. Novel phenanthrocarbazole based donor-acceptor random and alternating copolymers for photovoltaics. ACTA ACUST UNITED AC 2013. [DOI: 10.1002/pola.26917] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Zhiqiang Deng
- Institute of Polymers/Department of Chemistry, Nanchang University; 999 Xuefu Avenue Nanchang 330031 China
| | - Lie Chen
- Institute of Polymers/Department of Chemistry, Nanchang University; 999 Xuefu Avenue Nanchang 330031 China
- Jiangxi Provincial Key Laboratory of New Energy Chemistry; Nanchang University; 999 Xuefu Avenue Nanchang 330031 China
| | - Yiwang Chen
- Institute of Polymers/Department of Chemistry, Nanchang University; 999 Xuefu Avenue Nanchang 330031 China
- Jiangxi Provincial Key Laboratory of New Energy Chemistry; Nanchang University; 999 Xuefu Avenue Nanchang 330031 China
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48
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Sharenko A, Proctor CM, van der Poll TS, Henson ZB, Nguyen TQ, Bazan GC. A high-performing solution-processed small molecule:perylene diimide bulk heterojunction solar cell. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2013; 25:4403-4406. [PMID: 23788212 DOI: 10.1002/adma.201301167] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 05/01/2013] [Indexed: 06/02/2023]
Abstract
By combining the molecular donor p-DTS(FBTTh2 )2 with a readily produced perylene diimide acceptor we are able to achieve a power conversion efficiency of 3.0%, making this one of the most efficient non-fullerene organic solar cells to date. The reduced power conversion efficiency of the present system compared to the use of phenyl-C71 -butyric acid methyl ester as an electron acceptor is shown to primarily be related to a significant reduction in the internal quantum efficiency. These results indicate the potential of small-molecule:non-fullerene bulk-heterojunction organic photovoltaics.
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Affiliation(s)
- Alexander Sharenko
- Center for Polymers and Organic Solids, University of California, Santa Barbara, CA 93106, USA
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Vandewal K, Himmelberger S, Salleo A. Structural Factors That Affect the Performance of Organic Bulk Heterojunction Solar Cells. Macromolecules 2013. [DOI: 10.1021/ma400924b] [Citation(s) in RCA: 136] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Koen Vandewal
- Department
of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California
94305, United States
| | - Scott Himmelberger
- Department
of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California
94305, United States
| | - Alberto Salleo
- Department
of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California
94305, United States
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50
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Fischer FSU, Tremel K, Saur AK, Link S, Kayunkid N, Brinkmann M, Herrero-Carvajal D, Navarrete JTL, Delgado MCR, Ludwigs S. Influence of Processing Solvents on Optical Properties and Morphology of a Semicrystalline Low Bandgap Polymer in the Neutral and Charged States. Macromolecules 2013. [DOI: 10.1021/ma400939z] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- F. S. U. Fischer
- IPOC-Functional Polymers, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - K. Tremel
- IPOC-Functional Polymers, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - A.-K. Saur
- IPOC-Functional Polymers, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - S. Link
- IPOC-Functional Polymers, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - N. Kayunkid
- Institut Charles Sadron (UPR22), CNRS 23 rue du Loess, 67034 Strasbourg Cedex 2, France
| | - M. Brinkmann
- Institut Charles Sadron (UPR22), CNRS 23 rue du Loess, 67034 Strasbourg Cedex 2, France
| | - D. Herrero-Carvajal
- Department of Physical Chemistry, University of Málaga, Campus de Teatinos s/n,
Málaga 29071, Spain
| | - J. T. López Navarrete
- Department of Physical Chemistry, University of Málaga, Campus de Teatinos s/n,
Málaga 29071, Spain
| | - M. C. Ruiz Delgado
- Department of Physical Chemistry, University of Málaga, Campus de Teatinos s/n,
Málaga 29071, Spain
| | - S. Ludwigs
- IPOC-Functional Polymers, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
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