1
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Thapa GJ, Chauhan M, Cranston RR, Guo B, Lessard BH, Dougherty DB, Amassian A. Linking Electronic and Structural Disorder Parameters to Carrier Transport in a Modern Conjugated Polymer. ACS APPLIED MATERIALS & INTERFACES 2024; 16:48016-48024. [PMID: 39213484 DOI: 10.1021/acsami.4c10298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
Understanding charge transport in conjugated polymers is crucial for the development of next-generation organic electronic applications. It is presumed that structural disorder in conjugated polymers originating from their semicrystallinity, processing, or polymorphism leads to a complex energetic landscape that influences charge carrier transport properties. However, the link between polymer order parameters and energetic landscape is not well established experimentally. In this work, we successfully link statistical surveys of the local polymer electronic structure with paracrystalline structural disorder, a measure of statistical fluctuations away from the ideal polymer packing structure. We use scanning tunneling microscopy/spectroscopy to measure spatial variability in electronic band edges in PM6 films, a high-performance conjugated polymer, and find that films with higher paracrystallinity exhibit greater electronic disorder, as expected. In addition, we show that macroscopic charge carrier mobility in field effect transistors and and trap influence in hole-only diode devices is positively correlated with these microscopic structural and electronic parameters.
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Affiliation(s)
- Gaurab J Thapa
- Department of Materials Science and Engineering and Organic and Carbon Electronics Laboratories (ORaCEL), North Carolina State University, Raleigh, North Carolina 27695, United States
- Department of Physics and Organic and Carbon Electronics Laboratories (ORaCEL), North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Mihirsinh Chauhan
- Department of Materials Science and Engineering and Organic and Carbon Electronics Laboratories (ORaCEL), North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Rosemary R Cranston
- Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis Pasteur, Ottawa, ON K1N 6N5, Canada
| | - Boyu Guo
- Department of Materials Science and Engineering and Organic and Carbon Electronics Laboratories (ORaCEL), North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Benoît H Lessard
- Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis Pasteur, Ottawa, ON K1N 6N5, Canada
- School of Electrical Engineering and Computer Science, University of Ottawa, 800 King Edward Ave, Ottawa, ON K1N 6N5, Canada
| | - Daniel B Dougherty
- Department of Physics and Organic and Carbon Electronics Laboratories (ORaCEL), North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Aram Amassian
- Department of Materials Science and Engineering and Organic and Carbon Electronics Laboratories (ORaCEL), North Carolina State University, Raleigh, North Carolina 27695, United States
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2
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Maiti A, Pal AJ. Quasi-2D Ruddlesden-Popper Lead Halide Perovskites: How Edge Matters. J Phys Chem Lett 2022; 13:9875-9882. [PMID: 36251849 DOI: 10.1021/acs.jpclett.2c02739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A band-mapping technique is introduced to investigate the formation of low-energy edge states in quasi-2D Ruddlesden-Popper (RP) perovskites, (BA)2(MA)n-1PbnI3n+1, through a localized mode of measurement, namely, scanning tunneling spectroscopy. The local band structures measured at different points reveal the formation of 3D CH3NH3PbI3 (MAPbI3) at the edges of the perovskite nanosheets; for thin films, the 3D phase (n = ∞) could be seen to form at grain boundaries. The presence of MAPbI3 at the edges or grain boundaries of the perovskites has led to self-forming type-II band alignment in BA2MA2Pb3I10 (n = 3). The rationale behind achieving a high-efficiency solar cell based on the material, which has a large exciton binding energy, has been inferred. Kelvin probe force microscopy studies under illumination have yielded a higher surface photovoltage at the edges compared to the interior and supported the inference of exciton dissociation due to internal type-II band alignment in the quasi-2D RP perovskites.
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Affiliation(s)
- Abhishek Maiti
- School of Physical Sciences, Indian Association for the Cultivation of Science, Kolkata 700032, India
| | - Amlan J Pal
- School of Physical Sciences, Indian Association for the Cultivation of Science, Kolkata 700032, India
- UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001, India
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3
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Lee YR, Huang CC, Huang WY, Chen CT, Huang PT, Wang JK. Nanometer-scaled landscape of polymer: fullerene blends mapped with visible s-SNOM. NANOTECHNOLOGY 2022; 33:165702. [PMID: 34963107 DOI: 10.1088/1361-6528/ac46b5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 12/27/2021] [Indexed: 06/14/2023]
Abstract
Bulk heterojunction is one key concept leading to breakthrough in organic photovoltaics. The active layer is expectantly formed of distinct morphologies that carry out their respective roles in photovoltaic performance. The morphology-performance relationship however remains stymied, because unequivocal morphology at the nanoscale is not available. We used scattering-type scanning near-field optical microscopy operating with a visible light source (visibles-SNOM) to disclose the nanomorphology of P3HT:PCBM and pBCN:PCBM blends. Donor and acceptor domain as well as intermixed phase were identified and their intertwined distributions were mapped. We proposed energy landscapes of the BHJ active layer to shed light on the roles played by these morphologies in charge separation, transport and recombination. This study shows that visibles-SNOM is capable of profiling the morphological backdrop pertaining to the operation of high performance organic solar cells.
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Affiliation(s)
- Ya-Rong Lee
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
| | - Cheng-Chia Huang
- Department of Physics, National Taiwan University, Taipei, Taiwan
| | - Wen-Yu Huang
- Department of Physics, National Taiwan University, Taipei, Taiwan
| | - Chin-Ti Chen
- Institute of Chemistry, Academia Sinica, Taipei, Taiwan
| | - Ping-Tsung Huang
- Department of Chemistry, Fu-Jen Catholic University, New Taipei City, Taiwan
| | - Juen-Kai Wang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
- Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
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4
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Dulal R, Scougale WR, Chen W, Balasubramanian G, Chien T. Direct Observations of Uniform Bulk Heterojunctions and the Energy Level Alignments in Nonfullerene Organic Photovoltaic Active Layers. ACS APPLIED MATERIALS & INTERFACES 2021; 13:56430-56437. [PMID: 34786941 DOI: 10.1021/acsami.1c18426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
State-of-the-art organic photovoltaic (OPV) cells rely on the engineering of the energy levels of the organic molecules as well as the bulk-heterojunction nanomorphology to achieve high performance. However, both are difficult to measure inside the active layer where the electron donor and acceptor molecules are mingled. While the energy level alignments of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) between the electron donors and acceptors may be altered in the mixed active layer compared to their pure forms, the nanomorphology of the donor and acceptor molecular domains is mostly studied in indirect means. Here, we present the direct observations of the nanomorphology of the molecular domains as well as the energy level alignments in the active layer of a nonfullerene-based OPV (donor: PBDB-T-2F and acceptor: IT-4Cl) using cross-sectional scanning tunneling microscopy and spectroscopy (XSTM/S). It is revealed that (1) the bulk-heterojunction (BHJ) structures are homogeneous and uniform throughout the ∼1.2 μm thick active layer; (2) the energy alignments between the donor-rich and acceptor-rich domains are directly observed; (3) there exist the intermixing domains at the boundaries of the donor-rich and acceptor-rich domains with thickness in the nm scale; (4) the exciton binding energies in PBDB-T-2F and IT-4Cl are estimated to be 0.74 and 0.32 eV, respectively; and (5) there is an ∼0.7 V loss in the open circuit voltage. The results provide a nanoscale understanding of the OPV active layers to guide further improvement of the OPV performance.
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Affiliation(s)
- Rabindra Dulal
- Department of Physics & Astronomy, University of Wyoming, Laramie, Wyoming 82071, United States
| | - William R Scougale
- Department of Physics & Astronomy, University of Wyoming, Laramie, Wyoming 82071, United States
| | - Wei Chen
- Department of Mechanical Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Ganesh Balasubramanian
- Department of Mechanical Engineering & Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - TeYu Chien
- Department of Physics & Astronomy, University of Wyoming, Laramie, Wyoming 82071, United States
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5
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Peng W, Wang H, Lu H, Yin L, Wang Y, Grandidier B, Yang D, Pi X. Recent Progress on the Scanning Tunneling Microscopy and Spectroscopy Study of Semiconductor Heterojunctions. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2100655. [PMID: 34337855 DOI: 10.1002/smll.202100655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 05/18/2021] [Indexed: 06/13/2023]
Abstract
The band alignment, interface states, interface coupling, and carrier transport of semiconductor heterojunctions (SHs) need to be well understood for the design and fabrication of various important semiconductor structures and devices. Scanning tunneling microscopy (STM) with high spatial resolution and scanning tunneling spectroscopy (STS) with high energy resolution are significantly contributing to the understanding on the important properties of SHs. In this work, the recent progress on the use of STM and STS to study lateral, vertical and bulk SHs is reviewed. The spatial structures of SHs with atomically flat surface have been examined with STM. The electronic band structures (e. g., the band offset, interface state, and space charge region) of SHs are measured with STS. Combined with the spatial structures and the tunneling spectra features, the mechanism for the carrier transport in the SH may be proposed.
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Affiliation(s)
- Wenbing Peng
- State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China
| | - Haolin Wang
- State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China
| | - Hui Lu
- Institute of Advanced Semiconductors, Hangzhou Innovation Center, Zhejiang University, Hangzhou, Zhejiang, 311215, China
| | - Lei Yin
- State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China
| | - Yue Wang
- State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China
| | - Bruno Grandidier
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, Lille, 59000, France
| | - Deren Yang
- State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China
- Institute of Advanced Semiconductors, Hangzhou Innovation Center, Zhejiang University, Hangzhou, Zhejiang, 311215, China
| | - Xiaodong Pi
- State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China
- Institute of Advanced Semiconductors, Hangzhou Innovation Center, Zhejiang University, Hangzhou, Zhejiang, 311215, China
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6
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Sahare S, Ghoderao P, Khan SB, Chan Y, Lee SL. Recent progress in hybrid perovskite solar cells through scanning tunneling microscopy and spectroscopy. NANOSCALE 2020; 12:15970-15992. [PMID: 32761037 DOI: 10.1039/d0nr03499a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Currently, sustainable renewable energy sources are urgently required to fulfill the cumulative energy needs of the world's 7.8 billion population, since the conventional coal and fossil fuels will be exhausted soon. Photovoltaic devices are a direct and efficient means to produce a huge amount of energy to meet these energy targets. In particular, hybrid-perovskite-based photovoltaic devices merit special attention not only due to their exceptional efficiency for generating appreciable energy but also their tunable band gaps and the ease of device fabrication. However, the commercialization of such devices suffers from the instability of the compositional materials. The cause of instability is the perovskite's structure and its morphology at the sub-molecular level; thereby revealing and eliminating these instabilities are a striking challenge. To address this issue, scanning tunneling microscopy/spectroscopy (STM/STS) presents a comprehensive method to allow the visualization of the morphology and electronic structure of materials at atomic-level resolution. Here, we review the recent developments of perovskite-based solar cells (PSCs), the STM/STS analysis of photoactive halide/hybrid and oxide materials, and the real-time STM/STS investigation of electronic structures with defects and traps that are believed to mainly affect device performances. The detailed STM/STS analysis can facilitate a better understanding of the properties of materials at the nanoscale. This informative study may hold great promise to advance the development of stable PSCs under atmospheric conditions.
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Affiliation(s)
- Sanjay Sahare
- Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, 518060 China. and Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronics Engineering, Shenzhen University, Shenzhen, Guangdong, 518060 China
| | - Prachi Ghoderao
- Department of Applied Physics, Defence Institute of Advanced Technology, Pune, 411025 India
| | - Sadaf Bashir Khan
- Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, 518060 China. and Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronics Engineering, Shenzhen University, Shenzhen, Guangdong, 518060 China
| | - Yue Chan
- Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, 518060 China.
| | - Shern-Long Lee
- Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, 518060 China.
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7
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Interfacial Energetic Level Mapping and Nano-Ordering of Small Molecule/Fullerene Organic Solar Cells by Scanning Tunneling Microscopy and Spectroscopy. NANOMATERIALS 2020; 10:nano10030427. [PMID: 32121230 PMCID: PMC7152849 DOI: 10.3390/nano10030427] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 02/20/2020] [Accepted: 02/22/2020] [Indexed: 12/27/2022]
Abstract
Using scanning tunneling microscopy (STM) and spectroscopy (STS) at the liquid/solid interface, morphology evolution process and energetic level alignment of very thin solid films (thickness: <700 pm), of the low molecular weight molecule DRCN5T and DRCN5T:[70]PCBM blend are analyzed after applying thermal annealing at different temperatures. These films exhibit a worm-like pattern without thermal annealing (amorphous shape); however, after applying thermal annealing at 120 °C, the small molecule film domains crystallize verified by X-ray diffraction: structural geometry becomes a well-defined organized array. By using STS, the energy band diagrams of the semiconductor bulk heterojunction (blended film) at the donor-acceptor interface are determined; morphology and energy characteristics can be correlated with the organic solar cells (OSC) performance. When combining thermal treatment and solvent vapor annealing processes as described in previous literature by using other techniques, OSC devices based on DRCN5T show a very acceptable power conversion efficiency of 9.0%.
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8
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Chen X, Lai J, Shen Y, Chen Q, Chen L. Functional Scanning Force Microscopy for Energy Nanodevices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1802490. [PMID: 30133000 DOI: 10.1002/adma.201802490] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 06/29/2018] [Indexed: 06/08/2023]
Abstract
Energy nanodevices, including energy conversion and energy storage devices, have become a major cross-disciplinary field in recent years. These devices feature long-range electron and ion transport coupled with chemical transformation, which call for novel characterization tools to understand device operation mechanisms. In this context, recent developments in functional scanning force microscopy techniques and their application in thin-film photovoltaic devices and lithium batteries are reviewed. The advantages of scanning force microscopy, such as high spatial resolution, multimodal imaging, and the possibility of in situ and in operando imaging, are emphasized. The survey indicates that functional scanning force microscopy is making significant contributions in understanding materials and interfaces in energy nanodevices.
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Affiliation(s)
- Xi Chen
- i-Lab, CAS Center for Excellence in Nanoscience, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou, 215123, P. R. China
| | - Junqi Lai
- i-Lab, CAS Center for Excellence in Nanoscience, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou, 215123, P. R. China
| | - Yanbin Shen
- i-Lab, CAS Center for Excellence in Nanoscience, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou, 215123, P. R. China
- School of Nano Technology and Nano Bionics, University of Science and Technology of China (USTC), Hefei, 230026, China
| | - Qi Chen
- i-Lab, CAS Center for Excellence in Nanoscience, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou, 215123, P. R. China
- School of Nano Technology and Nano Bionics, University of Science and Technology of China (USTC), Hefei, 230026, China
| | - Liwei Chen
- i-Lab, CAS Center for Excellence in Nanoscience, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou, 215123, P. R. China
- School of Nano Technology and Nano Bionics, University of Science and Technology of China (USTC), Hefei, 230026, China
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9
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Gu KL, Zhou Y, Morrison WA, Park K, Park S, Bao Z. Nanoscale Domain Imaging of All-Polymer Organic Solar Cells by Photo-Induced Force Microscopy. ACS NANO 2018; 12:1473-1481. [PMID: 29338202 DOI: 10.1021/acsnano.7b07865] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Rapid nanoscale imaging of the bulk heterojunction layer in organic solar cells is essential to the continued development of high-performance devices. Unfortunately, commonly used imaging techniques such as tunneling electron microscopy (TEM) and atomic force microscopy (AFM) suffer from significant drawbacks. For instance, assuming domain identity from phase contrast or topographical features can lead to inaccurate morphological conclusions. Here we demonstrate a technique known as photo-induced force microscopy (PiFM) for imaging organic solar cell bulk heterojunctions with nanoscale chemical specificity. PiFM is a relatively recent scanning probe microscopy technique that combines an AFM tip with a tunable infrared laser to induce a dipole for chemical imaging. Coupling the nanometer resolution of AFM with the chemical specificity of a tuned IR laser, we are able to spatially map the donor and acceptor domains in a model all-polymer bulk heterojunction with resolution approaching 10 nm. Domain size from PiFM images is compared to bulk-averaged results from resonant soft X-ray scattering, indicating excellent quantitative agreement. Further, we demonstrate that in our all-polymer system, the AFM topography, AFM phase, and PiFM show poor correlation, highlighting the need to move beyond standard AFM for morphology characterization of bulk heterojunctions.
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Affiliation(s)
- Kevin L Gu
- Department of Chemical Engineering, Stanford University , Stanford, California 94305, United States
| | - Yan Zhou
- Department of Chemical Engineering, Stanford University , Stanford, California 94305, United States
| | - William A Morrison
- Molecular Vista , 6840 Via Del Oro, Suite 110, San Jose, California 95119, United States
| | - Katherine Park
- Molecular Vista , 6840 Via Del Oro, Suite 110, San Jose, California 95119, United States
| | - Sung Park
- Molecular Vista , 6840 Via Del Oro, Suite 110, San Jose, California 95119, United States
| | - Zhenan Bao
- Department of Chemical Engineering, Stanford University , Stanford, California 94305, United States
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10
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Alessandri R, Uusitalo JJ, de Vries AH, Havenith RWA, Marrink SJ. Bulk Heterojunction Morphologies with Atomistic Resolution from Coarse-Grain Solvent Evaporation Simulations. J Am Chem Soc 2017; 139:3697-3705. [PMID: 28209056 PMCID: PMC5355903 DOI: 10.1021/jacs.6b11717] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
![]()
Control
over the morphology of the active layer of bulk heterojunction
(BHJ) organic solar cells is paramount to achieve high-efficiency
devices. However, no method currently available can predict morphologies
for a novel donor–acceptor blend. An approach which allows
reaching relevant length scales, retaining chemical specificity, and
mimicking experimental fabrication conditions, and which is suited
for high-throughput schemes has been proven challenging to find. Here,
we propose a method to generate atom-resolved morphologies of BHJs
which conforms to these requirements. Coarse-grain (CG) molecular
dynamics simulations are employed to simulate the large-scale morphological
organization during solution-processing. The use of CG models which
retain chemical specificity translates into a direct path to the rational
design of donor and acceptor compounds which differ only slightly
in chemical nature. Finally, the direct retrieval of fully atomistic
detail is possible through backmapping, opening the way for improved
quantum mechanical calculations addressing the charge separation mechanism.
The method is illustrated for the poly(3-hexyl-thiophene) (P3HT)–phenyl-C61-butyric
acid methyl ester (PCBM) mixture, and found to predict morphologies
in agreement with experimental data. The effect of drying rate, P3HT
molecular weight, and thermal annealing are investigated extensively,
resulting in trends mimicking experimental findings. The proposed
methodology can help reduce the parameter space which has to be explored
before obtaining optimal morphologies not only for BHJ solar cells
but also for any other solution-processed soft matter device.
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Affiliation(s)
| | | | | | - Remco W A Havenith
- Ghent Quantum Chemistry Group, Department of Inorganic and Physical Chemistry, Ghent University , Krijgslaan 281 (S3), B-9000 Gent, Belgium
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11
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Kundu B, Bera A, Pal AJ. Differential conductance (dI/dV) imaging of a heterojunction-nanorod. NANOTECHNOLOGY 2017; 28:095705. [PMID: 28135209 DOI: 10.1088/1361-6528/aa58f0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Through scanning tunneling spectroscopy, we envisage imaging a heterostructure, namely a junction formed in a single nanorod. While the differential conductance spectrum provides location of conduction and valence band edges, dI/dV images record energy levels of materials. Such dI/dV images at different voltages allowed us to view p- and n-sections of heterojunction nanorods and more importantly the depletion region in such a junction that has a type-II band alignment. Viewing of selective sections in a heterojunction occurred due to band-bending in the junction and is correlated to the density of states spectrum of the individual semiconductors. The dI/dV images recorded at different voltages could be used to generate a band diagram of a pn junction.
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Affiliation(s)
- Biswajit Kundu
- Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
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12
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Sin DH, Ko H, Jo SB, Kim M, Bae GY, Cho K. Decoupling Charge Transfer and Transport at Polymeric Hole Transport Layer in Perovskite Solar Cells. ACS APPLIED MATERIALS & INTERFACES 2016; 8:6546-6553. [PMID: 26887635 DOI: 10.1021/acsami.5b12023] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Tailoring charge extraction interfaces in perovskite solar cells (PeSCs) critically determines the photovoltaic performance of PeSCs. Here, we investigated the decoupling of two major determinants of the efficient charge extraction, the charge transport and interfacial charge transfer properties at hole transport layers (HTLs). A simple physical tuning of a representative polymeric HTL, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), provided a wide range of charge conductivities from 10(-4) to 10(3) S cm(-1) without significant modulations in their energy levels, thereby enabling the decoupling of charge transport and transfer properties at HTLs. The transient photovoltaic response measurement revealed that the facilitation of hole transport through the highly conductive HTL promoted the elongation of charge carrier lifetimes within the PeSCs up to 3 times, leading to enhanced photocurrent extraction and finally 25% higher power conversion efficiency.
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Affiliation(s)
- Dong Hun Sin
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
| | - Hyomin Ko
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
| | - Sae Byeok Jo
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
| | - Min Kim
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
| | - Geun Yeol Bae
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
| | - Kilwon Cho
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
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13
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Kawashima E, Fujii M, Yamashita K. Thermal effect on the morphology and performance of organic photovoltaics. Phys Chem Chem Phys 2016; 18:26456-26465. [DOI: 10.1039/c6cp04019e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The morphology of organic photovoltaics (OPVs) is a significant factor in improving performance, and establishing a method for controlling morphology is necessary.
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Affiliation(s)
- Eisuke Kawashima
- Department of Chemical System Engineering
- Graduate School of Engineering
- The University of Tokyo
- Tokyo 113-8656
- Japan
| | - Mikiya Fujii
- Department of Chemical System Engineering
- Graduate School of Engineering
- The University of Tokyo
- Tokyo 113-8656
- Japan
| | - Koichi Yamashita
- Department of Chemical System Engineering
- Graduate School of Engineering
- The University of Tokyo
- Tokyo 113-8656
- Japan
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14
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Wang J, Zhang F, An Q, Sun Q, Zhang J, Hu B. Unique insight into phase separation in polymer solar cells from their electric characteristics. Phys Chem Chem Phys 2015; 17:29671-8. [DOI: 10.1039/c5cp05471k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A simple approach is proposed to investigate donor/acceptor phase separation based on the J–V curves of corresponding electron-only devices under forward or revise bias.
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Affiliation(s)
- Jian Wang
- Key Laboratory of Luminescence and Optical Information
- Ministry of Education
- Beijing Jiaotong University
- Beijing 100044
- China
| | - Fujun Zhang
- Key Laboratory of Luminescence and Optical Information
- Ministry of Education
- Beijing Jiaotong University
- Beijing 100044
- China
| | - Qiaoshi An
- Key Laboratory of Luminescence and Optical Information
- Ministry of Education
- Beijing Jiaotong University
- Beijing 100044
- China
| | - Qianqian Sun
- Key Laboratory of Luminescence and Optical Information
- Ministry of Education
- Beijing Jiaotong University
- Beijing 100044
- China
| | - Jian Zhang
- Department of Material Science and Technology
- Guangxi Key Laboratory of Information Materials
- Guilin University of Electronic Technology
- Guilin 541004
- China
| | - Bin Hu
- Key Laboratory of Luminescence and Optical Information
- Ministry of Education
- Beijing Jiaotong University
- Beijing 100044
- China
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He M, Wang M, Lin C, Lin Z. Optimization of molecular organization and nanoscale morphology for high performance low bandgap polymer solar cells. NANOSCALE 2014; 6:3984-3994. [PMID: 24481029 DOI: 10.1039/c3nr06298h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Rational design and synthesis of low bandgap (LBG) polymers with judiciously tailored HOMO and LUMO levels have emerged as a viable route to high performance polymer solar cells with power conversion efficiencies (PCEs) exceeding 10%. In addition to engineering the energy-level of LBG polymers, the photovoltaic performance of LBG polymer-based solar cells also relies on the device architecture, in particular the fine morphology of the photoactive layer. The nanoscale interpenetrating networks composed of nanostructured donor and acceptor phases are the key to providing a large donor-acceptor interfacial area for maximizing the exciton dissociation and offering a continuous pathway for charge transport. In this Review Article, we summarize recent strategies for tuning the molecular organization and nanoscale morphology toward an enhanced photovoltaic performance of LBG polymer-based solar cells.
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Affiliation(s)
- Ming He
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
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16
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Bera A, Dey S, Pal AJ. Band mapping across a pn-junction in a nanorod by scanning tunneling microscopy. NANO LETTERS 2014; 14:2000-2005. [PMID: 24588335 DOI: 10.1021/nl500081m] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We map band-edges across a pn-junction that was formed in a nanorod. We form a single junction between p-type Cu2S and n-type CdS through a controlled cationic exchange process of CdS nanorods. We characterize nanorods of the individual materials and the single junction in a nanorod with an ultrahigh vacuum scanning tunneling microscope (UHV-STM) at 77 K. From scanning tunneling spectroscopy and correspondingly the density of states (DOS) spectra, we determine the conduction and valence band-edges at different points across the junction and the individual nanorods. We could map the band-diagram of nanorod-junctions to bring out the salient features of a diode, such as p- and n-sections, band-bending, depletion region, albeit interestingly in the nanoscale.
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Affiliation(s)
- Abhijit Bera
- Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
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17
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Katsiev K, Ip AH, Fischer A, Tanabe I, Zhang X, Kirmani AR, Voznyy O, Rollny LR, Chou KW, Thon SM, Carey GH, Cui X, Amassian A, Dowben P, Sargent EH, Bakr OM. The complete in-gap electronic structure of colloidal quantum dot solids and its correlation with electronic transport and photovoltaic performance. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:937-42. [PMID: 24243769 DOI: 10.1002/adma.201304166] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 09/30/2013] [Indexed: 05/25/2023]
Abstract
The direct observation of the complete electronic band structure of a family of PbS CQD solids via photoelectron spectroscopy is reported. We investigate how materials processing strategies, such as the latest passivation methods that produce record-performance photovoltaics, achieve their performance advances. Halide passivated films show a drastic reduction in states in the midgap, contributing to a marked improvement in the device performance.
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Affiliation(s)
- Khabiboulakh Katsiev
- Division of Physical Sciences and Engineering, Solar and Photovoltaic Engineering Center, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
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