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Chen R, Ni C, Zhu J, Fan F, Li C. Surface photovoltage microscopy for mapping charge separation on photocatalyst particles. Nat Protoc 2024:10.1038/s41596-024-00992-2. [PMID: 38654135 DOI: 10.1038/s41596-024-00992-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Accepted: 02/22/2024] [Indexed: 04/25/2024]
Abstract
Solar-driven photocatalytic reactions offer a promising route to clean and sustainable energy, and the spatial separation of photogenerated charges on the photocatalyst surface is the key to determining photocatalytic efficiency. However, probing the charge-separation properties of photocatalysts is a formidable challenge because of the spatially heterogeneous microstructures, complicated charge-separation mechanisms and lack of sensitivity for detecting the low density of separated photogenerated charges. Recently, we developed surface photovoltage microscopy (SPVM) with high spatial and energy resolution that enables the direct mapping of surface-charge distributions and quantitative assessment of the charge-separation properties of photocatalysts at the nanoscale, potentially providing unprecedented insights into photocatalytic charge-separation processes. Here, this protocol presents detailed procedures that enable researchers to construct the SPVM instruments by integrating Kelvin probe force microscopy with an illumination system and the modulated surface photovoltage (SPV) approach. It then describes in detail how to perform SPVM measurements on actual photocatalyst particles, including sample preparation, tuning of the microscope, adjustment of the illuminated light path, acquisition of SPVM images and measurements of spatially resolved modulated SPV signals. Moreover, the protocol also includes sophisticated data analysis that can guide non-experts in understanding the microscopic charge-separation mechanisms. The measurements are ordinarily performed on photocatalysts with a conducting substrate in gases or vacuum and can be completed in 15 h.
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Affiliation(s)
- Ruotian Chen
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
| | - Chenwei Ni
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jian Zhu
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
| | - Fengtao Fan
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
| | - Can Li
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
- University of Chinese Academy of Sciences, Beijing, China.
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Murphy JG, Raybin JG, Sibener SJ. Correlating polymer structure, dynamics, and function with atomic force microscopy. JOURNAL OF POLYMER SCIENCE 2022. [DOI: 10.1002/pol.20210321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Julia G. Murphy
- The James Franck Institute and Department of Chemistry The University of Chicago Chicago Illinois USA
| | - Jonathan G. Raybin
- The James Franck Institute and Department of Chemistry The University of Chicago Chicago Illinois USA
| | - Steven J. Sibener
- The James Franck Institute and Department of Chemistry The University of Chicago Chicago Illinois USA
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Schumacher Z, Rejali R, Cowie M, Spielhofer A, Miyahara Y, Grutter P. Charge Carrier Inversion in a Doped Thin Film Organic Semiconductor Island. ACS NANO 2021; 15:10377-10383. [PMID: 34048210 DOI: 10.1021/acsnano.1c02600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Inducing an inversion layer in organic semiconductors is a highly nontrivial, but critical, achievement for producing organic field-effect transistor (OFET) devices, which rely on the generation of inversion, accumulation, and depletion regimes for successful operation. Here, we develop a pulsed bias technique to characterize the dopant type of any organic material system, without prior knowledge or characterization of the material in question. We use this technique on a pentacene/PTCDI heterostructure and thus deduce that pentacene is exhibiting n-doped like response. The source of the additional charges in the pentacene island can be identified by charging rings in the dissipation channel of the noncontact atomic force microscopy (AFM) signal, a typical signature for localized charge transfer from the AFM tip to the sample. Additionally, through tip-induced band-bending, we generate inversion, depletion, and accumulation regimes over a 20 nm radius, three monolayer thick n-doped pentacene island. Our findings demonstrate that nanometer-scale lateral extent and thickness are sufficient for an OFET device to operate in the inversion regime.
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Affiliation(s)
- Zeno Schumacher
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | - Rasa Rejali
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | - Megan Cowie
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | - Andreas Spielhofer
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | - Yoichi Miyahara
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | - Peter Grutter
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
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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: 10] [Impact Index Per Article: 1.7] [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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Chen R, Fan F, Dittrich T, Li C. Imaging photogenerated charge carriers on surfaces and interfaces of photocatalysts with surface photovoltage microscopy. Chem Soc Rev 2018; 47:8238-8262. [DOI: 10.1039/c8cs00320c] [Citation(s) in RCA: 214] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Recent advances in imaging and characterizing charge separation on surfaces and interfaces of photocatalysts by surface photovoltage spectroscopy were reviewed and highlighted.
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Affiliation(s)
- Ruotian Chen
- State Key Laboratory of Catalysis
- Dalian National Laboratory for Clean Energy
- The Collaborative Innovation Centre of Chemistry for Energy Materials (iChEM)
- Dalian Institute of Chemical Physics
- Chinese Academy of Sciences
| | - Fengtao Fan
- State Key Laboratory of Catalysis
- Dalian National Laboratory for Clean Energy
- The Collaborative Innovation Centre of Chemistry for Energy Materials (iChEM)
- Dalian Institute of Chemical Physics
- Chinese Academy of Sciences
| | - Thomas Dittrich
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH
- Institut für Silizium-Photovoltaik
- 12489 Berlin
- Germany
| | - Can Li
- State Key Laboratory of Catalysis
- Dalian National Laboratory for Clean Energy
- The Collaborative Innovation Centre of Chemistry for Energy Materials (iChEM)
- Dalian Institute of Chemical Physics
- Chinese Academy of Sciences
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Dwyer RP, Nathan SR, Marohn JA. Microsecond photocapacitance transients observed using a charged microcantilever as a gated mechanical integrator. SCIENCE ADVANCES 2017; 3:e1602951. [PMID: 28691085 PMCID: PMC5479705 DOI: 10.1126/sciadv.1602951] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 04/17/2017] [Indexed: 05/29/2023]
Abstract
How light is converted to electricity in blends of organic donor and acceptor molecules is an unsettled question, partly because the spatial heterogeneity present in these blends makes them challenging to characterize. Although scanned-probe measurements have provided crucially important microscopic insights into charge generation and transport in these blends, achieving the subnanosecond time resolution needed to directly observe the fate of photogenerated charges has proven difficult. We use a charged microcantilever as a gated mechanical integrator to record photocapacitance indirectly by measuring the accumulated change in cantilever phase as a function of the time delay between precisely synchronized voltage and light pulses. In contrast with previous time-resolved scanned-probe photocapacitance measurements, the time resolution of this method is set by the rise and fall time of the voltage and light pulses and not by the inverse detection bandwidth. We demonstrate in an organic donor-acceptor blend the ability of this indirect, "phase-kick" technique to record multiexponential photocapacitance transients on time scales ranging from 40 μs to 10 ms. The technique's ability to measure subcycle, nanosecond charge dynamics is demonstrated by measuring the tens of nanosecond sample electrical charging time.
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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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Cox PA, Glaz MS, Harrison JS, Peurifoy SR, Coffey DC, Ginger DS. Imaging Charge Transfer State Excitations in Polymer/Fullerene Solar Cells with Time-Resolved Electrostatic Force Microscopy. J Phys Chem Lett 2015; 6:2852-2858. [PMID: 26267169 DOI: 10.1021/acs.jpclett.5b01360] [Citation(s) in RCA: 9] [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
We demonstrate nanoscale imaging of charge transfer state photoexcitations in polymer/fullerene bulk heterojunction solar cells using time-resolved electrostatic force microscopy (trEFM). We compare local trEFM charging rates and external quantum efficiencies (EQE) for both above-gap and below-gap excitation of the model system poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM). We show that the local trEFM charging rate correlates with device EQE for both above-gap and below-gap photoexcitation, demonstrating that EFM methods have sufficient sensitivity to detect the low EQEs associated with CT state formation, a result that could be useful for probing weak subgap excitations in nanostructured materials such as quantum dot and organometal halide perovskite solar cells. Further, we use trEFM to map spatial variations in EQE arising from subgap CT excitation in organic photovoltaics (OPVs) and find that the local distribution of photocurrent arising from these states is nearly identical to the spatial variation in EQE from above-gap singlet excitation. These results are consistent with recent work showing that both above-gap and below-gap excitation have similar internal quantum efficiency.
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Affiliation(s)
- Phillip A Cox
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Micah S Glaz
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Jeffrey S Harrison
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Samuel R Peurifoy
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - David C Coffey
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - David S Ginger
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
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10
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Li Y, Xu CY, Wang JY, Zhen L. Photodiode-like behavior and excellent photoresponse of vertical Si/monolayer MoS2 heterostructures. Sci Rep 2014; 4:7186. [PMID: 25424301 PMCID: PMC4244624 DOI: 10.1038/srep07186] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 10/29/2014] [Indexed: 12/21/2022] Open
Abstract
Monolayer transition metal dichalcogenides (TMDs) and their van der Waals heterostructures have been experimentally and theoretically demonstrated as potential candidates for photovoltaic and optoelectronic devices due to the suitable bandgap and excellent light absorption. In this work, we report the observation of photodiode behavior in (both n- and p- type) silicon/monolayer MoS2 vertical heterostructures. The photocurrent and photoresponsivity of heterostructures photodiodes were dependent both on the incident light wavelength and power density, and the highest photoresponsivity of 7.2 A/W was achieved in n-Si/monolayer MoS2 vertical heterostructures photodiodes. Compared with n-Si/MoS2 heterostructures, the photoresponsivity of p-Si/MoS2 heterostructure was much lower. Kelvin probe microscope (KFM) results demonstrated the more efficient separation of photogenerated excitons in n-Si/MoS2 than that in p-Si/MoS2. Coupling KFM results with band alignments of (p-, n-) Si/MoS2 heterostructures, the origins of photodiode-like phenomena of p-Si/MoS2 and n-Si/MoS2 have been unveiled, that is intrinsic built-in electric field in p-n junction, and modulated barrier height and width at the interface in n-n junction. Our work may benefit to the deep understanding of the integration of two-dimensional materials with more conventional three-dimensional semiconductors, and then contribute to the developments in the area of van der Waals heterostructures.
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Affiliation(s)
- Yang Li
- School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Cheng-Yan Xu
- 1] School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China [2] MOE Key Laboratory of Micro-systems and Micro-structures Manufacturing, Harbin Institute of Technology, Harbin 150080, China
| | - Jia-Ying Wang
- School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Liang Zhen
- 1] School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China [2] MOE Key Laboratory of Micro-systems and Micro-structures Manufacturing, Harbin Institute of Technology, Harbin 150080, China
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Takacs CJ, Collins SD, Love JA, Mikhailovsky AA, Wynands D, Bazan GC, Nguyen TQ, Heeger AJ. Mapping orientational order in a bulk heterojunction solar cell with polarization-dependent photoconductive atomic force microscopy. ACS NANO 2014; 8:8141-51. [PMID: 25080374 DOI: 10.1021/nn502277d] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
New methods connecting molecular structure, self-organization, and optoelectronic performance are important for understanding the current generation of organic photovoltaic (OPV) materials. In high power conversion efficiency (PCE) OPVs, light-harvesting small-molecules or polymers are typically blended with fullerene derivatives and deposited in thin films, forming a bulk heterojunction (BHJ), a self-assembled three-dimensional nanostructure of electron donors and acceptors that separates and transports charges. Recent data suggest micrometer-scale orientational order of donor domains exists within this complex nanomorphology, but the link to the optoelectronic properties is yet unexplored. Here we introduce polarization-dependent, photoconductive atomic force microscopy (pd-pcAFM) as a combined probe of orientational order and nanoscale optoelectronic properties (∼20 nm resolution). Using the donor 7,7'-(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b']dithiophene-2,6-diyl)bis(6-fluoro-4-(5'-hexyl[2,2'-bithiophen]-5-yl)benzo[c][1,2,5]thiadiazole), p-DTS(FBTTh2)2, we show significant spatial dependence of the nanoscale photocurrent with polarized light in both pristine and BHJ blends (up to 7.0% PCE) due to the local alignment of the molecular transition dipoles. By mapping the polarization dependence of the nanoscale photocurrent, we estimate the molecular orientation and orientational order parameter. Liquid crystalline disclinations are observed in all films, in agreement with complementary electron microscopy experiments, and the order parameter exceeds 0.3. The results demonstrate the utility of pd-pcAFM to investigate the optical/structural anisotropy that exists within a well-performing BHJ system and its relationship to optoelectronic properties on both the nanometer and micrometer length scales.
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Affiliation(s)
- Christopher J Takacs
- Department of Physics, ∞Department of Chemistry and Biochemistry and ‡Center for Polymers and Organic Solids, University of California Santa Barbara , Santa Barbara, California 93106, United States
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Pershin A, Donets S, Baeurle SA. Photocurrent contribution from inter-segmental mixing in donor–acceptor-type polymer solar cells: A multiscale simulation study. POLYMER 2014. [DOI: 10.1016/j.polymer.2014.06.038] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Watanabe S, Fukuchi Y, Fukasawa M, Sassa T, Kimoto A, Tajima Y, Uchiyama M, Yamashita T, Matsumoto M, Aoyama T. In situ KPFM imaging of local photovoltaic characteristics of structured organic photovoltaic devices. ACS APPLIED MATERIALS & INTERFACES 2014; 6:1481-1487. [PMID: 24450927 DOI: 10.1021/am4038992] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Here, we discuss the local photovoltaic characteristics of a structured bulk heterojunction, organic photovoltaic devices fabricated with a liquid carbazole, and a fullerene derivative based on analysis by scanning kelvin probe force microscopy (KPFM). Periodic photopolymerization induced by an interference pattern from two laser beams formed surface relief gratings (SRG) in the structured films. The surface potential distribution in the SRGs indicates the formation of donor and acceptor spatial distribution. Under illumination, the surface potential reversibly changed because of the generation of fullerene anions and hole transport from the films to substrates, which indicates that we successfully imaged the local photovoltaic characteristics of the structured photovoltaic devices. Using atomic force microscopy, we confirmed the formation of the SRG because of the material migration to the photopolymerized region of the films, which was induced by light exposure through photomasks. The structuring technique allows for the direct fabrication and the control of donor and acceptor spatial distribution in organic photonic and electronic devices with minimized material consumption. This in situ KPFM technique is indispensable to the fabrication of nanoscale electron donor and electron acceptor spatial distribution in the devices.
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Affiliation(s)
- Satoshi Watanabe
- Department of Materials Science and Technology, Tokyo University of Science , 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585, Japan
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Liscio A. Scanning Probe Microscopy beyond Imaging: A General Tool for Quantitative Analysis. Chemphyschem 2013; 14:1283-92. [DOI: 10.1002/cphc.201200880] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 01/23/2013] [Indexed: 11/12/2022]
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