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Bergmann VW, Guo Y, Tanaka H, Hermes IM, Li D, Klasen A, Bretschneider SA, Nakamura E, Berger R, Weber SAL. Local Time-Dependent Charging in a Perovskite Solar Cell. ACS APPLIED MATERIALS & INTERFACES 2016; 8:19402-19409. [PMID: 27377472 DOI: 10.1021/acsami.6b04104] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Efficient charge extraction within solar cells explicitly depends on the optimization of the internal interfaces. Potential barriers, unbalanced charge extraction, and interfacial trap states can prevent cells from reaching high power conversion efficiencies. In the case of perovskite solar cells, slow processes happening on time scales of seconds cause hysteresis in the current-voltage characteristics. In this work, we localized and investigated these slow processes using frequency-modulation Kelvin probe force microscopy (FM-KPFM) on cross sections of planar methylammonium lead iodide (MAPI) perovskite solar cells. FM-KPFM can map the charge density distribution and its dynamics at internal interfaces. Upon illumination, space charge layers formed at the interfaces of the selective contacts with the MAPI layer within several seconds. We observed distinct differences in the charging dynamics at the interfaces of MAPI with adjacent layers. Our results indicate that more than one process is involved in hysteresis. This finding is in agreement with recent simulation studies claiming that a combination of ion migration and interfacial trap states causes the hysteresis in perovskite solar cells. Such differences in the charging rates at different interfaces cannot be separated by conventional device measurements.
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Affiliation(s)
- Victor W Bergmann
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
| | - Yunlong Guo
- Department of Chemistry, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hideyuki Tanaka
- Department of Chemistry, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Ilka M Hermes
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
| | - Dan Li
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
| | - Alexander Klasen
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
| | | | - Eiichi Nakamura
- Department of Chemistry, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Rüdiger Berger
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
| | - Stefan A L Weber
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
- Institute of Physics, Johannes Gutenberg University Mainz , Duesbergweg 10-14, 55128 Mainz, Germany
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52
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Garrett JL, Munday JN. Fast, high-resolution surface potential measurements in air with heterodyne Kelvin probe force microscopy. NANOTECHNOLOGY 2016; 27:245705. [PMID: 27159082 DOI: 10.1088/0957-4484/27/24/245705] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Kelvin probe force microscopy (KPFM) adapts an atomic force microscope to measure electric potential on surfaces at nanometer length scales. Here we demonstrate that Heterodyne-KPFM enables scan rates of several frames per minute in air, and concurrently maintains spatial resolution and voltage sensitivity comparable to frequency-modulation KPFM, the current spatial resolution standard. Two common classes of topography-coupled artifacts are shown to be avoidable with H-KPFM. A second implementation of H-KPFM is also introduced, in which the voltage signal is amplified by the first cantilever resonance for enhanced sensitivity. The enhanced temporal resolution of H-KPFM can enable the imaging of many dynamic processes, such as such as electrochromic switching, phase transitions, and device degredation (battery, solar, etc), which take place over seconds to minutes and involve changes in electric potential at nanometer lengths.
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Affiliation(s)
- Joseph L Garrett
- University of Maryland Department of Physics, College Park, MD 20742, USA. Institute for Research in Electronics and Applied Physics, College Park, MD 20742, USA
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53
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Karatay DU, Harrison JS, Glaz MS, Giridharagopal R, Ginger DS. Fast time-resolved electrostatic force microscopy: Achieving sub-cycle time resolution. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:053702. [PMID: 27250430 DOI: 10.1063/1.4948396] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The ability to measure microsecond- and nanosecond-scale local dynamics below the diffraction limit with widely available atomic force microscopy hardware would enable new scientific studies in fields ranging from biology to semiconductor physics. However, commercially available scanning-probe instruments typically offer the ability to measure dynamics only on time scales of milliseconds to seconds. Here, we describe in detail the implementation of fast time-resolved electrostatic force microscopy using an oscillating cantilever as a means to measure fast local dynamics following a perturbation to a sample. We show how the phase of the oscillating cantilever relative to the perturbation event is critical to achieving reliable sub-cycle time resolution. We explore how noise affects the achievable time resolution and present empirical guidelines for reducing noise and optimizing experimental parameters. Specifically, we show that reducing the noise on the cantilever by using photothermal excitation instead of piezoacoustic excitation further improves time resolution. We demonstrate the discrimination of signal rise times with time constants as fast as 10 ns, and simultaneous data acquisition and analysis for dramatically improved image acquisition times.
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Affiliation(s)
- Durmus U Karatay
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
| | - Jeffrey S Harrison
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
| | - Micah S Glaz
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
| | - Rajiv Giridharagopal
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
| | - David S Ginger
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
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54
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Collins L, Belianinov A, Somnath S, Rodriguez BJ, Balke N, Kalinin SV, Jesse S. Multifrequency spectrum analysis using fully digital G Mode-Kelvin probe force microscopy. NANOTECHNOLOGY 2016; 27:105706. [PMID: 26866505 DOI: 10.1088/0957-4484/27/10/105706] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Since its inception over two decades ago, Kelvin probe force microscopy (KPFM) has become the standard technique for characterizing electrostatic, electrochemical and electronic properties at the nanoscale. In this work, we present a purely digital, software-based approach to KPFM utilizing big data acquisition and analysis methods. General mode (G-Mode) KPFM works by capturing the entire photodetector data stream, typically at the sampling rate limit, followed by subsequent de-noising, analysis and compression of the cantilever response. We demonstrate that the G-Mode approach allows simultaneous multi-harmonic detection, combined with on-the-fly transfer function correction-required for quantitative CPD mapping. The KPFM approach outlined in this work significantly simplifies the technique by avoiding cumbersome instrumentation optimization steps (i.e. lock in parameters, feedback gains etc), while also retaining the flexibility to be implemented on any atomic force microscopy platform. We demonstrate the added advantages of G-Mode KPFM by allowing simultaneous mapping of CPD and capacitance gradient (C') channels as well as increased flexibility in data exploration across frequency, time, space, and noise domains. G-Mode KPFM is particularly suitable for characterizing voltage sensitive materials or for operation in conductive electrolytes, and will be useful for probing electrodynamics in photovoltaics, liquids and ionic conductors.
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Affiliation(s)
- Liam Collins
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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55
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Pershin A, Szalay PG. Development of highly accurate approximate scheme for computing the charge transfer integral. J Chem Phys 2015; 143:074109. [DOI: 10.1063/1.4928053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Anton Pershin
- Laboratory for Theoretical Chemistry, Institute of Chemistry, Eötvös Loránd University, P.O. Box 32, H-1518 Budapest, Hungary
| | - Péter G. Szalay
- Laboratory for Theoretical Chemistry, Institute of Chemistry, Eötvös Loránd University, P.O. Box 32, H-1518 Budapest, Hungary
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56
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Dou L, Liu Y, Hong Z, Li G, Yang Y. Low-Bandgap Near-IR Conjugated Polymers/Molecules for Organic Electronics. Chem Rev 2015; 115:12633-65. [PMID: 26287387 DOI: 10.1021/acs.chemrev.5b00165] [Citation(s) in RCA: 531] [Impact Index Per Article: 59.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Letian Dou
- Department of Materials Science and Engineering, and ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States
| | - Yongsheng Liu
- Department of Materials Science and Engineering, and ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States
| | - Ziruo Hong
- Department of Materials Science and Engineering, and ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States
| | - Gang Li
- Department of Materials Science and Engineering, and ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States
| | - Yang Yang
- Department of Materials Science and Engineering, and ‡California NanoSystems Institute, University of California , Los Angeles, California 90095, United States
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57
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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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58
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Baghgar M, Barnes MD. Work Function Modification in P3HT H/J Aggregate Nanostructures Revealed by Kelvin Probe Force Microscopy and Photoluminescence Imaging. ACS NANO 2015; 9:7105-7112. [PMID: 26095304 DOI: 10.1021/acsnano.5b03422] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We show that surface electronic properties of poly-3-hexylthiophene (P3HT) crystalline nanofibers as probed by Kelvin probe force microscopy (KPFM) depends sensitively on the degree of polymer packing order and dominant coupling type (e.g., H- or J-aggregate) as signaled by absorption or photoluminescence spectroscopy. Nominal HOMO energies between high molecular weight (J-aggregate) nanofibers and low-molecular weight (H-aggregate) nanofibers differ by ≈160 meV. This is consistent with shifts expected from H-type charge-transfer (CT) interactions that lower HOMO energies according to registration between thiophene moieties on adjacent polymer chains. These results show how KPFM combined with wavelength-resolved photoluminescence imaging can be used to extract information on "dark" (CT) interactions in polymer assemblies.
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Affiliation(s)
- Mina Baghgar
- †Department of Physics and ‡Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Michael D Barnes
- †Department of Physics and ‡Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
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59
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Studying biological membranes with extended range high-speed atomic force microscopy. Sci Rep 2015; 5:11987. [PMID: 26169348 PMCID: PMC4500952 DOI: 10.1038/srep11987] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 05/11/2015] [Indexed: 11/28/2022] Open
Abstract
High—speed atomic force microscopy has proven to be a valuable tool for the study of biomolecular systems at the nanoscale. Expanding its application to larger biological specimens such as membranes or cells has, however, proven difficult, often requiring fundamental changes in the AFM instrument. Here we show a way to utilize conventional AFM instrumentation with minor alterations to perform high-speed AFM imaging with a large scan range. Using a two—actuator design with adapted control systems, a 130 × 130 × 5 μm scanner with nearly 100 kHz open—loop small-signal Z—bandwidth is implemented. This allows for high-speed imaging of biologically relevant samples as well as high-speed measurements of nanomechanical surface properties. We demonstrate the system performance by real-time imaging of the effect of charged polymer nanoparticles on the integrity of lipid membranes at high imaging speeds and peak force tapping measurements at 32 kHz peak force rate.
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60
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Zhu J, Fan F, Chen R, An H, Feng Z, Li C. Direct Imaging of Highly Anisotropic Photogenerated Charge Separations on Different Facets of a Single BiVO4Photocatalyst. Angew Chem Int Ed Engl 2015; 54:9111-4. [DOI: 10.1002/anie.201504135] [Citation(s) in RCA: 232] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Indexed: 01/05/2023]
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61
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Zhu J, Fan F, Chen R, An H, Feng Z, Li C. Direct Imaging of Highly Anisotropic Photogenerated Charge Separations on Different Facets of a Single BiVO4Photocatalyst. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201504135] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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62
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Balke N, Maksymovych P, Jesse S, Kravchenko II, Li Q, Kalinin SV. Exploring local electrostatic effects with scanning probe microscopy: implications for piezoresponse force microscopy and triboelectricity. ACS NANO 2014; 8:10229-36. [PMID: 25257028 DOI: 10.1021/nn505176a] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The implementation of contact mode Kelvin probe force microscopy (cKPFM) utilizes the electrostatic interactions between tip and sample when the tip and sample are in contact with each other. Surprisingly, the electrostatic forces in contact are large enough to be measured even with tips as stiff as 4.5 N/m. As for traditional noncontact KPFM, the signal depends strongly on electrical properties of the sample, such as the dielectric constant, and the tip properties, such as the stiffness. Since the tip is in contact with the sample, bias-induced changes in the junction potential between tip and sample can be measured with higher lateral and temporal resolution compared to traditional noncontact KPFM. Significant and reproducible variations of tip-surface capacitance are observed and attributed to surface electrochemical phenomena. Observations of significant surface charge states at zero bias and strong hysteretic electromechanical responses at a nonferroelectric surface have significant implications for fields such as triboelectricity and piezoresponse force microscopy.
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Affiliation(s)
- Nina Balke
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Rige, Tennessee 37831, United States
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63
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Shao G, Glaz MS, Ma F, Ju H, Ginger DS. Intensity-modulated scanning Kelvin probe microscopy for probing recombination in organic photovoltaics. ACS NANO 2014; 8:10799-10807. [PMID: 25207675 DOI: 10.1021/nn5045867] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We study surface photovoltage decays on sub-millisecond time scales in organic solar cells using intensity-modulated scanning Kelvin probe microscopy (SKPM). Using polymer/fullerene (poly[N-9"-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]/[6,6]-phenyl C71-butyric acid methyl ester, PCDTBT/PC71BM) bulk heterojunction devices as a test case, we show that the decay lifetimes measured by SKPM depend on the intensity of the background illumination. We propose that this intensity dependence is related to the well-known carrier-density-dependent recombination kinetics in organic bulk heterojunction materials. We perform transient photovoltage (TPV) and charge extraction (CE) measurements on the PCDTBT/PC71BM blends to extract the carrier-density dependence of the recombination lifetime in our samples, and we find that the device TPV and CE data are in good agreement with the intensity and frequency dependence observed via SKPM. Finally, we demonstrate the capability of intensity-modulated SKPM to probe local recombination rates due to buried interfaces in organic photovoltaics (OPVs). We measure the differences in photovoltage decay lifetimes over regions of an OPV cell fabricated on an indium tin oxide electrode patterned with two different phosphonic acid monolayers known to affect carrier lifetime.
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Affiliation(s)
- Guozheng Shao
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
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64
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Chen Q, Lu W, Wu YK, Ding HY, Wang B, Chen L. Probe the Effects of Surface Adsorbates on ZnO Nanowire Conductivity using Dielectric Force Microscopy. CHINESE J CHEM PHYS 2014. [DOI: 10.1063/1674-0068/27/05/582-586] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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65
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Parizi SS, Mellinger A, Caruntu G. Ferroelectric barium titanate nanocubes as capacitive building blocks for energy storage applications. ACS APPLIED MATERIALS & INTERFACES 2014; 6:17506-17517. [PMID: 25255863 DOI: 10.1021/am502547h] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Highly uniform polymer-ceramic nanocomposite films with high energy density values were fabricated by exploiting the unique ability of monodomain, nonaggregated BaTiO3 colloidal nanocrystals to function as capacitive building blocks when dispersed into a weakly interacting dielectric matrix. Monodisperse, surface-functionalized ferroelectric 15 nm BaTiO3 nanoparticles have been selectively incorporated with a high packing density into poly(vinylidene fluoride-co-hexafluoropropene) (P(VDF-HFP)) leading to the formation of biphasic BaTiO3-P(VDF-HFP) nanocomposite films. A systematic investigation of the electrical properties of the nanocomposites by electrostatic force microscopy and conventional dielectric measurements reveals that polymer-ceramic film capacitor structures exhibit a ferroelectric relaxor-type behavior with an increased intrinsic energy density. The composite containing 7% BaTiO3 nanocrystals displays a high permittivity (ε = 21) and a relatively high energy density (E = 4.66 J/cm(3)) at 150 MV/m, which is 166% higher than that of the neat polymer and exceeds the values reported in the literature for polymer-ceramic nanocomposites containing a similar amount of nanoparticle fillers. The easy processing and electrical properties of the polymer-ceramic nanocomposites make them suitable for implementation in pulse power capacitors, high power systems and other energy storage applications.
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Affiliation(s)
- Saman Salemizadeh Parizi
- Department of Chemistry and Biochemistry and the Science of Advanced Materials (SAM) Program, Central Michigan University , Mt. Pleasant, Michigan 48858, United States
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66
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67
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Baghgar M, Barnes AM, Pentzer E, Wise AJ, Hammer BAG, Emrick T, Dinsmore AD, Barnes MD. Morphology-dependent electronic properties in cross-linked (P3HT-b-P3MT) block copolymer nanostructures. ACS NANO 2014; 8:8344-8349. [PMID: 25003706 DOI: 10.1021/nn502806d] [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
Combined Kelvin probe force microscopy and wavelength-resolved photoluminescence measurements on individual pre- and post-cross-linked poly(3-hexylthiophene)-b-poly(3-methyl alcohol thiophene) (P3HT-b-P3MT) nanofibers have revealed striking differences in their optical and electronic properties driven by structural perturbation of the crystalline aggregate nanofiber structures after cross-linking. Chemical cross-linking from diblock copolymer P3HT-b-P3MT using a hexamethylene diisocyanate cross-linker produces a variety of morphologies including very small nanowires, nanofiber bundles, nanoribbons, and sheets, whose relative abundance can be controlled by reaction time and cross-linker concentration. While the different cross-linked morphologies have almost identical photophysical characteristics, KPFM measurements show that the surface potential contrast, related to the work function of the sample, depends sensitively on nanostructure morphology related to chain-packing disorder.
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Affiliation(s)
- Mina Baghgar
- Departments of Physics, ‡Polymer Science and Engineering, and §Chemistry, University of Massachusetts , Amherst, Massachusetts 01003, United States
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68
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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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69
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Wu S, Wu Z, Lin D, Zhong Z, Jiang Z, Yang X. Photogenerated charges and surface potential variations investigated on single Si nanorods by electrostatic force microscopy combined with laser irradiation. NANOSCALE RESEARCH LETTERS 2014; 9:245. [PMID: 24940176 PMCID: PMC4035825 DOI: 10.1186/1556-276x-9-245] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Accepted: 05/07/2014] [Indexed: 06/02/2023]
Abstract
Photogenerated charging properties of single Si nanorods (Si NRs) are investigated by electrostatic force microscopy (EFM) combined with laser irradiation. Under laser irradiation, Si NRs are positively charged. The amount of the charges trapped in single NRs as well as the contact potential difference between the tip and NRs' surface is achieved from an analytical fitting of the phase shift - voltage curve. Both of them significantly vary with the laser intensity and the NR's size and construction. The photogenerated charging and decharging rates are obtained at a timescale of seconds or slower, indicating that the Si NRs are promising candidates in photovoltaic applications.
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Affiliation(s)
- Shan Wu
- State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
| | - Zilong Wu
- State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
| | - Dongdong Lin
- State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
| | - Zhenyang Zhong
- State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
| | - Zuimin Jiang
- State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
| | - Xinju Yang
- State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
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70
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Ostrowski DP, Vanden Bout DA. Correlation of morphology with photocurrent generation in a polymer blend photovoltaic device. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2014; 10:1821-1829. [PMID: 24482361 DOI: 10.1002/smll.201303262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 11/15/2013] [Indexed: 06/03/2023]
Abstract
Morphological effects on photovoltaic (PV) properties are studied through scanning photocurrent (PC) and photoluminescence (PL) microscopy of a solution processed, polymer blend PV device composed of PFB [poly(9,9'-dioctylfluorene-co-bis-N,N-(4-butylphenyl)-bis-N,N-phenyl-1,4-phenylenediamine] and F8BT [poly(9,9'-dioctylfluorene-co-benzothiadiazole]. As PFB and F8BT have unique absorbance bands, it is possible to selectively excite only F8BT (488 nm) or both PFB and F8BT (408 nm). Local voltage-dependent photocurrent (LVPC) measurements from particular regions of interest in the PV show that the diode characteristics between different morphologies are essentially the same, except in regard to the magnitude of PC generated. A local PL spectrum is measured simultaneously with PC generation at each pixel in the image maps. Through integration of the local PL spectrum over particular wavelength ranges, PL image maps are created of PFB-PL (435 to 475 nm), F8BT-PL (530 to 570 nm), exciplex-PL (620 to 685 nm) and total-PL (entire spectrum). These data allow direct correlation of PC generation with local chemical composition variations within the PV device. PL image maps show morphological variations on the order of 0.5 to 1 µm of alternating PFB-rich and F8BT-rich phases. While illuminating only F8BT (488 nm light), the PFB-rich phases produce the most PC, however, while illuminating both polymers but mostly PFB (408 nm light), the F8BT-rich phases produce the most PC. These results show that in the morphology where the light absorbing material is less concentrated, the PC generation is increased. Additionally, the exciplex-PL is found to not be a significant radiative loss mechanism of charge carriers for PC generation.
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Affiliation(s)
- David P Ostrowski
- Department of Chemistry and Biochemistry and the Center for Nano and Molecular Science, at The University of Texas at Austin, Welch Hall 2.204, 105 E. 24th Street, A5300, Austin, TX, 78712-1224, USA
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71
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Orgiu E, Samorì P. 25th anniversary article: organic electronics marries photochromism: generation of multifunctional interfaces, materials, and devices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:1827-1845. [PMID: 24554562 DOI: 10.1002/adma.201304695] [Citation(s) in RCA: 153] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 01/13/2014] [Indexed: 06/03/2023]
Abstract
Organic semiconductors have garnered significant interest as key components for flexible, low-cost, and large-area electronics. Hitherto, both materials and processing thereof seems to head towards a mature technology which shall ultimately meet expectations and efforts built up over the past years. However, by its own organic electronics cannot compete or complement the silicon-based electronics in integrating multiple functions in a small area unless novel solutions are brought into play. Photochromic molecules are small organic molecules able to undergo reversible photochemical isomerization between (at least) two (meta)stable states which exhibit markedly different properties. They can be embedded as additional component in organic-based materials ready to be exploited in devices such as OLEDs, OFETs, and OLETs. The structurally controlled incorporation of photochromic molecules can be done at various interfaces of a device, including the electrode/semiconductor or dielectric/semiconductor interface, or even as a binary mixture in the active layer, in order to impart a light responsive nature to the device. This can be accomplished by modulating via a light stimulus fundamental physico-chemical properties such as charge injection and transport in the device.
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Affiliation(s)
- Emanuele Orgiu
- Nanochemistry Laboratory, ISIS & icFRC, Université de Strasbourg & CNRS, 8 allée Gaspard Monge, 67000, Strasbourg, France
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72
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Performance enhancement of block-copolymer solar cells through tapering the donor–acceptor interface: A multiscale study. POLYMER 2014. [DOI: 10.1016/j.polymer.2014.01.052] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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73
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Strelcov E, Ievlev AV, Jesse S, Kravchenko II, Shur VY, Kalinin SV. Direct probing of charge injection and polarization-controlled ionic mobility on ferroelectric LiNbO(3) surfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:958-63. [PMID: 24277472 DOI: 10.1002/adma.201304002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 08/26/2013] [Indexed: 05/14/2023]
Abstract
Mapping surface potential with time-resolved Kelvin probe force microscopy (tr-KPFM) in LiNbO3 periodically poled single crystals reveals activation of the surface ionic subsystem. Electric fields of certain strength induce injection of charge, formation of an active region in its vicinity and uneven distribution of screening charge on the opposite ferroelectric domains. Tr-KPFM technique allows investigating these phenomena in details.
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Affiliation(s)
- Evgheni Strelcov
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, United States
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74
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Nanoscale structural and electronic evolution for increased efficiency in polymer solar cells monitored by electric scanning probe microscopy. CHINESE SCIENCE BULLETIN-CHINESE 2014. [DOI: 10.1007/s11434-013-0040-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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75
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Yan H, Li D, He C, Wei Z, Yang Y, Li Y. A material combination principle for highly efficient polymer solar cells investigated by mesoscopic phase heterogeneity. NANOSCALE 2013; 5:11649-11656. [PMID: 24096725 DOI: 10.1039/c3nr03165a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Organic solar cells have become a promising energy conversion candidate because of their unique advantages. Novel fullerene derivatives, as a common acceptor, can increase power conversion efficiency (PCE) by increasing the open-circuit voltage. As a representative acceptor, Indene-C60 bisadduct (ICBA) can reach high efficiency with poly(3-hexylthiophene) (P3HT). On the other hand, the novel synthesized polymers mainly aimed to broaden the optical absorption range have steadily promoted efficiency to higher than 9%. However, it is challenging to obtain the desired result by simply combining ICBA with other high-efficiency donors. Thus, P3HT or a high-efficiency polymer PBDTTT-C-T (copolymer of thienyl-substituted BDT with substituted TT) is used as donor and PCBM or ICBA as acceptor in this article to clarify the mechanism behind these materials. The optical and photovoltaic properties of the materials are studied for pair-wise combination. Among these four material groups, the highest PCE of 6.2% is obtained for the PBDTTT-C-T/PCBM combination while the lowest PCE of 3.5% is obtained for the PBDTTT-C-T/ICBA combination. The impact of the mesoscopic heterogeneity on the local mesoscopic photoelectric properties is identified by photo-conductive AFM (pc-AFM), and the consistence between the mesoscopic properties and the macroscopic device performances is also observed. Based on these results, an interface combined model is proposed based on the mesoscopic phase heterogeneity. This study provides a new view on the rational selection of photovoltaic materials, where, aside from the traditional energy level and absorption spectrum matching, the matching of mesoscopic heterogeneity must also be considered.
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Affiliation(s)
- Han Yan
- National Center for Nanoscience and Technology, Beijing 100190, P. R. China.
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76
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Collins L, Kilpatrick JI, Weber SAL, Tselev A, Vlassiouk IV, Ivanov IN, Jesse S, Kalinin SV, Rodriguez BJ. Open loop Kelvin probe force microscopy with single and multi-frequency excitation. NANOTECHNOLOGY 2013; 24:475702. [PMID: 24176878 DOI: 10.1088/0957-4484/24/47/475702] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Conventional Kelvin probe force microscopy (KPFM) relies on closed loop (CL) bias feedback for the determination of surface potential (SP). However, SP measured by CL-KPFM has been shown to be strongly influenced by the choice of measurement parameters due to non-electrostatic contributions to the input signal of the bias feedback loop. This often leads to systematic errors of several hundred mV and can also result in topographical crosstalk. Here, open loop (OL)-KPFM modes are investigated as a means of obtaining a quantitative, crosstalk free measurement of the SP of graphene grown on Cu foil, and are directly contrasted with CL-KPFM. OL-KPFM operation is demonstrated in both single and multi-frequency excitation regimes, yielding quantitative SP measurements. The SP difference between single and multilayer graphene structures using OL-KPFM was found to be 63 ± 11 mV, consistent with values previously reported by CL-KPFM. Furthermore, the same relative potential difference between Al2O3-coated graphene and Al2O3-coated Cu was observed using both CL and OL techniques. We observed an offset of 55 mV between absolute SP values obtained by OL and CL techniques, which is attributed to the influence of non-electrostatic contributions to the input of the bias feedback used in CL-KPFM.
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Affiliation(s)
- L Collins
- School of Physics, University College Dublin, Belfield, Dublin 4, Ireland. Conway Institute of Biomedical and Biomolecular Research, University College Dublin, Belfield, Dublin 4, Ireland
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77
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Lilliu S, Maragliano C, Hampton M, Elliott M, Stefancich M, Chiesa M, Dahlem MS, Macdonald JE. EFM data mapped into 2D images of tip-sample contact potential difference and capacitance second derivative. Sci Rep 2013; 3:3352. [PMID: 24284731 PMCID: PMC3842085 DOI: 10.1038/srep03352] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 11/08/2013] [Indexed: 11/09/2022] Open
Abstract
We report a simple technique for mapping Electrostatic Force Microscopy (EFM) bias sweep data into 2D images. The method allows simultaneous probing, in the same scanning area, of the contact potential difference and the second derivative of the capacitance between tip and sample, along with the height information. The only required equipment consists of a microscope with lift-mode EFM capable of phase shift detection. We designate this approach as Scanning Probe Potential Electrostatic Force Microscopy (SPP-EFM). An open-source MATLAB Graphical User Interface (GUI) for images acquisition, processing and analysis has been developed. The technique is tested with Indium Tin Oxide (ITO) and with poly(3-hexylthiophene) (P3HT) nanowires for organic transistor applications.
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Affiliation(s)
- S Lilliu
- 1] School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF243AA, United Kingdom [2] Masdar Institute of Science and Technology, PO Box 54224, Abu Dhabi, United Arab Emirates
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78
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Cox PA, Waldow DA, Dupper TJ, Jesse S, Ginger DS. Mapping nanoscale variations in photochemical damage of polymer/fullerene solar cells with dissipation imaging. ACS NANO 2013; 7:10405-10413. [PMID: 24138326 DOI: 10.1021/nn404920t] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We use frequency-modulated electrostatic force microscopy to track changes in cantilever quality factor (Q) as a function of photochemical damage in a model organic photovoltaic system poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7) and 3'H-cyclopropa[8,25][5,6]fullerene-C71-D5h(6)-3'-butanoic acid, 3'-phenyl-, methyl ester (PC71BM). We correlate local Q factor imaging with macroscopic device performance and show that, for this system, changes in cantilever Q correlate well with changes in external quantum efficiency and can thus be used to monitor local photochemical damage over the entire functional lifetime of a PTB7:PC71BM solar cell. We explore how Q imaging is affected by the choice of cantilever resonance frequency. Finally, we use Q imaging to elucidate the differences in the evolution of nanoscale structure in the photochemical damage occurring in PTB7:PC71BM solar cells processed with and without the solvent additive 1,8-diiodooctane (DIO). We show that processing with DIO not only yields a preferable morphology for uniform performance across the surface of the device but also enhances the stability of PTB7:PC71BM solar cells-an effect that can be predicted based on the local Q images.
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Affiliation(s)
- Phillip A Cox
- Department of Chemistry, University of Washington , Seattle, Washington 98195, United States
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79
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Zhang X, Li H. Laser-induced selective crosslinking for scaling the heterointerfacial domain in polymer blends. OPTICS EXPRESS 2013; 21:24620-24629. [PMID: 24150306 DOI: 10.1364/oe.21.024620] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Organic blends containing heterojunction structures at the interfacial phase have been applied extensively in organic optoelectronic devices to modify charge transfer, separation, and recombination processes. Scaling and controlling the transition domains at the hetero-interface are of crucial importance for deep insights into the involved physics and for architecturing the devices with improved performance. However, it is difficult to recognize and characterize these transition domains directly using the conventional microscopic techniques, in particular when different molecules are dissolved in the same solvent with equal solubility. In this work, we introduce a technique defined as laser-induced selective cross-linking to isolate the interfacial phase from other phases into a directly measurable practicity. Thus, the hetero-domains become visualized and directly measurable. Based on the insolubility of the selectively cross-linked molecules in organic solvents, a lift-off process may remove the uncross-linked or incompletely cross-linked molecules, so that the hetero-domain is more clearly visualized and more precisely measured. A transition domain in a scale of about 200 nm is resolved in the F8BT/PFB blend film between their respectively rich phases after the selective cross-linking of the F8BT molecules by a blue laser. Furthermore, hetero-crosslinking between F8BT and PFB molecules was also resolved by both microscopic and near-field spectroscopic investigations.
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80
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Warren SC, Voïtchovsky K, Dotan H, Leroy CM, Cornuz M, Stellacci F, Hébert C, Rothschild A, Grätzel M. Identifying champion nanostructures for solar water-splitting. NATURE MATERIALS 2013; 12:842-9. [PMID: 23832125 DOI: 10.1038/nmat3684] [Citation(s) in RCA: 253] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Accepted: 05/13/2013] [Indexed: 05/20/2023]
Abstract
Charge transport in nanoparticle-based materials underlies many emerging energy-conversion technologies, yet assessing the impact of nanometre-scale structure on charge transport across micrometre-scale distances remains a challenge. Here we develop an approach for correlating the spatial distribution of crystalline and current-carrying domains in entire nanoparticle aggregates. We apply this approach to nanoparticle-based α-Fe₂O₃ electrodes that are of interest in solar-to-hydrogen energy conversion. In correlating structure and charge transport with nanometre resolution across micrometre-scale distances, we have identified the existence of champion nanoparticle aggregates that are most responsible for the high photoelectrochemical activity of the present electrodes. Indeed, when electrodes are fabricated with a high proportion of these champion nanostructures, the electrodes achieve the highest photocurrent of any metal oxide photoanode for photoelectrochemical water-splitting under 100 mW cm(-2) air mass 1.5 global sunlight.
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Affiliation(s)
- Scott C Warren
- 1] Laboratory of Photonics and Interfaces, École Polytechnique Fédérale de Lausanne, Lausanne 1015, Switzerland [2]
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81
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Strelcov E, Jesse S, Huang YL, Teng YC, Kravchenko II, Chu YH, Kalinin SV. Space- and time-resolved mapping of ionic dynamic and electroresistive phenomena in lateral devices. ACS NANO 2013; 7:6806-6815. [PMID: 23837694 DOI: 10.1021/nn4017873] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A scanning probe microscopy-based technique for probing local ionic and electronic transport and their dynamic behavior on the 10 ms to 10 s scale is presented. The time-resolved Kelvin probe force microscopy (tr-KPFM) allows mapping of surface potential in both space and time domains, visualizing electronic and ionic charge dynamics and separating underlying processes based on their time responses. Here, tr-KPFM is employed to explore the interplay of the adsorbed surface ions and bulk oxygen vacancies and their role in the resistive switching in a Ca-substituted bismuth ferrite thin film.
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Affiliation(s)
- Evgheni Strelcov
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
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82
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Berger R, Domanski AL, Weber SA. Electrical characterization of organic solar cell materials based on scanning force microscopy. Eur Polym J 2013. [DOI: 10.1016/j.eurpolymj.2013.03.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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83
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High internal quantum efficiency in fullerene solar cells based on crosslinked polymer donor networks. Nat Commun 2013; 3:1321. [PMID: 23271655 PMCID: PMC3535333 DOI: 10.1038/ncomms2211] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Accepted: 10/17/2012] [Indexed: 11/24/2022] Open
Abstract
The power conversion efficiency of organic photovoltaic cells depends crucially on the morphology of their donor–acceptor heterostructure. Although tremendous progress has been made to develop new materials that better cover the solar spectrum, this heterostructure is still formed by a primitive spontaneous demixing that is rather sensitive to processing and hence difficult to realize consistently over large areas. Here we report that the desired interpenetrating heterostructure with built-in phase contiguity can be fabricated by acceptor doping into a lightly crosslinked polymer donor network. The resultant nanotemplated network is highly reproducible and resilient to phase coarsening. For the regioregular poly(3-hexylthiophene):phenyl-C61-butyrate methyl ester donor–acceptor model system, we obtained 20% improvement in power conversion efficiency over conventional demixed biblend devices. We reached very high internal quantum efficiencies of up to 0.9 electron per photon at zero bias, over an unprecedentedly wide composition space. Detailed analysis of the power conversion, power absorbed and internal quantum efficiency landscapes reveals the separate contributions of optical interference and donor–acceptor morphology effects. The conversion efficiency of organic solar cells depends on the shape of the interface between their donor and acceptor components. Liu et al. demonstrate a scalable method using crosslinked polymer networks to fabricate the finely interpenetrating structures needed to achieve near-perfect internal quantum efficiency.
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84
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Dou F, Silva C, Zhang X. Charge percolation pathways in polymer blend photovoltaic diodes with sub-mesoscopic two-phase microstructures. Chem Phys Lett 2013. [DOI: 10.1016/j.cplett.2013.03.076] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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85
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Zhang Q, Deng X, Qian PZG, Wang X. Spatial modeling for refining and predicting surface potential mapping with enhanced resolution. NANOSCALE 2013; 5:921-926. [PMID: 23299834 DOI: 10.1039/c2nr33603k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Quantitatively mapping surface properties with nanometer or even subnanometer resolutions is critical for advanced scanning probe microscopy (SPM) characterization. However, the characterization performance often suffers from noises and artifacts due to instrumentation or environmental limitations. In this paper, we proposed a novel statistical approach with bivariate spatial modeling to efficiently refine and predict surface property mapping. Scanning Kelvin probe microscopy (SKPM) was selected as a representative example to test our proposed method on lateral nanowire assemblies. We revealed that the proposed method can effectively retrieve the artifact-free surface potential distribution by automatically identifying topological artifacts from surface potential maps. Furthermore, the statistical model built upon low spatial resolution was successfully used to predict the potential values from higher-resolution topography data. Compared to conventional regression model, our model is able to predict the surface potential distribution from less raw data but yields much higher accuracy. Through this means, the spatial resolution of SKPM surface potential maps can be significantly improved. This statistics-enabled predictive method opens a new route toward high-precision and high-resolution SPM characterizations without the enhancement of instrumentation capabilities.
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Affiliation(s)
- Qiong Zhang
- Department of Statistics, University of Wisconsin-Madison, USA
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86
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Shao G, Rayermann GE, Smith EM, Ginger DS. Morphology-Dependent Trap Formation in Bulk Heterojunction Photodiodes. J Phys Chem B 2013; 117:4654-60. [DOI: 10.1021/jp3090843] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Guozheng Shao
- Department of Chemistry, University of Washington, Seattle Washington 98195, United States
| | - Glennis E. Rayermann
- Department of Chemistry, University of Washington, Seattle Washington 98195, United States
| | - Eric M. Smith
- 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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87
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Prokscha T, Chow KH, Stilp E, Suter A, Luetkens H, Morenzoni E, Nieuwenhuys GJ, Salman Z, Scheuermann R. Photo-induced persistent inversion of germanium in a 200-nm-deep surface region. Sci Rep 2013; 3:2569. [PMID: 23995307 PMCID: PMC3759057 DOI: 10.1038/srep02569] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 08/19/2013] [Indexed: 11/17/2022] Open
Abstract
The controlled manipulation of the charge carrier concentration in nanometer thin layers is the basis of current semiconductor technology and of fundamental importance for device applications. Here we show that it is possible to induce a persistent inversion from n- to p-type in a 200-nm-thick surface layer of a germanium wafer by illumination with white and blue light. We induce the inversion with a half-life of ~12 hours at a temperature of 220 K which disappears above 280 K. The photo-induced inversion is absent for a sample with a 20-nm-thick gold capping layer providing a Schottky barrier at the interface. This indicates that charge accumulation at the surface is essential to explain the observed inversion. The contactless change of carrier concentration is potentially interesting for device applications in opto-electronics where the gate electrode and gate oxide could be replaced by the semiconductor surface.
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Affiliation(s)
- T Prokscha
- Paul Scherrer Institute, Laboratory for Muon Spin Spectroscopy, Villigen PSI, Switzerland.
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88
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De Luca G, Liscio A, Battagliarin G, Chen L, Scolaro LM, Müllen K, Samorì P, Palermo V. Orthogonal self-assembly and selective solvent vapour annealing: simplified processing of a photovoltaic blend. Chem Commun (Camb) 2013; 49:4322-4. [DOI: 10.1039/c2cc37909k] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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89
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Luria JL, Hoepker N, Bruce R, Jacobs AR, Groves C, Marohn JA. Spectroscopic imaging of photopotentials and photoinduced potential fluctuations in a bulk heterojunction solar cell film. ACS NANO 2012; 6:9392-9401. [PMID: 23030548 DOI: 10.1021/nn300941f] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present spatially resolved photovoltage spectra of a bulk heterojunction solar cell film composed of phase-separated poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT) and poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine) (PFB) polymers prepared on ITO/PEDOT:PSS and aluminum substrates. Over both PFB- and F8BT-rich domains, the photopotential spectra were found to be proportional to a linear combination of the polymers' absorption spectra. Charge trapping in the film was studied using photopotential fluctuation spectroscopy, in which low-frequency photoinduced electrostatic potential fluctuations were measured by observing noise in the oscillation frequency of a nearby charged atomic force microscope cantilever. Over both F8BT- and PFB-rich regions, the magnitude, distance dependence, frequency dependence, and illumination wavelength dependence of the observed cantilever frequency noise are consistent with photopotential fluctuations arising from stochastic light-driven trapping and detrapping of charges in F8BT. Taken together, our findings suggest a microscopic mechanism by which intermixing of phases leads to charge trapping and thereby to suppressed open-circuit voltage and decreased efficiency in this prototypical bulk heterojunction solar cell film.
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Affiliation(s)
- Justin L Luria
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
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90
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Blinn KS, Li X, Liu M, Bottomley LA, Liu M. Probing and mapping electrode surfaces in solid oxide fuel cells. J Vis Exp 2012:e50161. [PMID: 23023264 DOI: 10.3791/50161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen (1-7). The performance of SOFCs and the rates of many chemical and energy transformation processes in energy storage and conversion devices in general are limited primarily by charge and mass transfer along electrode surfaces and across interfaces. Unfortunately, the mechanistic understanding of these processes is still lacking, due largely to the difficulty of characterizing these processes under in situ conditions. This knowledge gap is a chief obstacle to SOFC commercialization. The development of tools for probing and mapping surface chemistries relevant to electrode reactions is vital to unraveling the mechanisms of surface processes and to achieving rational design of new electrode materials for more efficient energy storage and conversion(2). Among the relatively few in situ surface analysis methods, Raman spectroscopy can be performed even with high temperatures and harsh atmospheres, making it ideal for characterizing chemical processes relevant to SOFC anode performance and degradation(8-12). It can also be used alongside electrochemical measurements, potentially allowing direct correlation of electrochemistry to surface chemistry in an operating cell. Proper in situ Raman mapping measurements would be useful for pin-pointing important anode reaction mechanisms because of its sensitivity to the relevant species, including anode performance degradation through carbon deposition(8, 10, 13, 14) ("coking") and sulfur poisoning(11, 15) and the manner in which surface modifications stave off this degradation(16). The current work demonstrates significant progress towards this capability. In addition, the family of scanning probe microscopy (SPM) techniques provides a special approach to interrogate the electrode surface with nanoscale resolution. Besides the surface topography that is routinely collected by AFM and STM, other properties such as local electronic states, ion diffusion coefficient and surface potential can also be investigated(17-22). In this work, electrochemical measurements, Raman spectroscopy, and SPM were used in conjunction with a novel test electrode platform that consists of a Ni mesh electrode embedded in an yttria-stabilized zirconia (YSZ) electrolyte. Cell performance testing and impedance spectroscopy under fuel containing H2S was characterized, and Raman mapping was used to further elucidate the nature of sulfur poisoning. In situ Raman monitoring was used to investigate coking behavior. Finally, atomic force microscopy (AFM) and electrostatic force microscopy (EFM) were used to further visualize carbon deposition on the nanoscale. From this research, we desire to produce a more complete picture of the SOFC anode.
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Affiliation(s)
- Kevin S Blinn
- Center for Innovative Fuel Cells and Battery Technologies, School of Materials Science and Engineering, Georgia Institute of Technology, GA, USA
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91
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Li D, Xing Y, Yue H, Zhang J, Ai X. Influence of nanostructure on the device performance and charge recombination dynamics of P3HT:PCBM solar cells. CHINESE SCIENCE BULLETIN-CHINESE 2012. [DOI: 10.1007/s11434-012-5204-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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92
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Lucas M, Riedo E. Invited review article: combining scanning probe microscopy with optical spectroscopy for applications in biology and materials science. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:061101. [PMID: 22755608 DOI: 10.1063/1.4720102] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
This is a comprehensive review of the combination of scanning probe microscopy (SPM) with various optical spectroscopies, with a particular focus on Raman spectroscopy. Efforts to combine SPM with optical spectroscopy will be described, and the technical difficulties encountered will be examined. These efforts have so far focused mainly on the development of tip-enhanced Raman spectroscopy, a powerful technique to detect and image chemical signatures with single molecule sensitivity, which will be reviewed. Beyond tip-enhanced Raman spectroscopy and/or topography measurements, combinations of SPM with optical spectroscopy have a great potential in the characterization of structure and quantitative measurements of physical properties, such as mechanical, optical, or electrical properties, in delicate biological samples and nanomaterials. The different approaches to improve the spatial resolution, the chemical sensitivity, and the accuracy of physical properties measurements will be discussed. Applications of such combinations for the characterization of structure, defects, and physical properties in biology and materials science will be reviewed. Due to the versatility of SPM probes for the manipulation and characterization of small and/or delicate samples, this review will mainly focus on the apertureless techniques based on SPM probes.
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Affiliation(s)
- Marcel Lucas
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA.
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93
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Pershin A, Donets S, Baeurle SA. A new multiscale modeling method for simulating the loss processes in polymer solar cell nanodevices. J Chem Phys 2012; 136:194102. [DOI: 10.1063/1.4712622] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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94
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Alexe M. Local mapping of generation and recombination lifetime in BiFeO3 single crystals by scanning probe photoinduced transient spectroscopy. NANO LETTERS 2012; 12:2193-2198. [PMID: 22468626 DOI: 10.1021/nl300618e] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Carrier lifetime in photoelectric processes is the average time an excited carrier is free before recombining or trapping. Lifetime is directly related to defects and it is a key parameter in analyzing photovoltaic effects in semiconductors. We show here a scanning probe method combined with photoinduced current spectroscopy that allows mapping with nanoscale resolution of the generation and recombination lifetimes. Using this method we have analyzed the mechanism of the abnormal photovoltaic effect in multiferroic bismuth ferrite, BiFeO(3). We found that generation and recombination lifetimes in BiFeO(3) are large due to complex generation and recombination processes that involve shallow energy levels in the band gap. The domain walls do not play a major role in the photovoltaic mechanism.
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Affiliation(s)
- Marin Alexe
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany.
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95
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Mizutani N, Korposh S, Selyanchyn R, Yang DH, Lee CS, Lee SW, Kunitake T. One-step Fabrication of Polystyrene–TiO2 Nanosandwich Film by Phase Separation. CHEM LETT 2012. [DOI: 10.1246/cl.2012.552] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Naoki Mizutani
- Graduate School of Environmental Engineering, The University of Kitakyushu
| | - Sergiy Korposh
- Graduate School of Environmental Engineering, The University of Kitakyushu
| | - Roman Selyanchyn
- Graduate School of Environmental Engineering, The University of Kitakyushu
| | - Do-Hyeon Yang
- Graduate School of Environmental Engineering, The University of Kitakyushu
| | - Chang-Soo Lee
- Bionanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology
| | - Seung-Woo Lee
- Graduate School of Environmental Engineering, The University of Kitakyushu
| | - Toyoki Kunitake
- Kitakyushu Foundation for the Advancement of Industry, Science and Technology
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96
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Lecover R, Williams N, Markovic N, Reich DH, Naiman DQ, Katz HE. Next-generation polymer solar cell materials: designed control of interfacial variables. ACS NANO 2012; 6:2865-2870. [PMID: 22444948 DOI: 10.1021/nn301140w] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Organic bulk heterojunction solar cells (BHJSCs) are the focus of a burgeoning research effort. While extensive characterization is performed in the course of many reported experimental studies, correlation of performance and physical parameters among studies done in different laboratories is low, pointing out the need to address some aspects of BHJSC active materials that have received relatively little attention. This Perspective describes how a new polymer additive series described by Lobez et al. in this issue of ACS Nano, along with some emerging morphological tools and scanning electronic nanoprobes, can help fill in some of this needed insight. A brief statistical discussion of interstudy correlations and a summary of past work on additives and interfacial studies are presented.
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Affiliation(s)
- Rachel Lecover
- Department of Materials Science and Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
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97
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Wong CTO, Lo SS, Huang L. Ultrafast Spatial Imaging of Charge Dynamics in Heterogeneous Polymer Blends. J Phys Chem Lett 2012; 3:879-884. [PMID: 26286414 DOI: 10.1021/jz300178g] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Proof-of-concept transient absorption microscopy (TAM) with simultaneously high spatial and temporal resolution was demonstrated to image charge generation and recombination in model systems of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends upon extended thermal annealing. Significant spatial heterogeneity in charge generation and recombination dynamics was revealed on the length scale of hundreds of nanometers near the micrometer-sized PCBM crystallites, suggesting that information obtained in ensemble measurements by integrating over microscopically inhomogeneous areas could be misleading. In contrast to previous studies, high sensitivity of our instrumentation allows us to employ low excitation intensities to minimize higher-order recombination processes. TAM provides a unique noncontact tool to probe local functionality in microscopically heterogeneous energy harvesting systems.
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Affiliation(s)
- Chris Tsz On Wong
- †Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Shun Shang Lo
- ‡Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Libai Huang
- †Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, United States
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98
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Guo S, Kalinin SV, Jesse S. Open-loop band excitation Kelvin probe force microscopy. NANOTECHNOLOGY 2012; 23:125704. [PMID: 22407131 DOI: 10.1088/0957-4484/23/12/125704] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
A multidimensional scanning probe microscopy approach for quantitative, cross-talk free mapping of surface electrostatic properties is demonstrated. Open-loop band excitation Kelvin probe force microscopy (OL BE KPFM) probes the full response-frequency-potential surface at each pixel at standard imaging rates. The subsequent analysis reconstructs work function, tip-surface capacitance gradient and resonant frequency maps, obviating feedback-related artifacts. OL BE KPFM imaging is demonstrated for several materials systems with topographic, potential and combined contrast. This approach combines the features of both frequency and amplitude KPFM and allows complete decoupling of topographic and voltage contributions to the KPFM signal.
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Affiliation(s)
- Senli Guo
- The Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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99
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Giridharagopal R, Rayermann GE, Shao G, Moore DT, Reid OG, Tillack AF, Masiello DJ, Ginger DS. Submicrosecond time resolution atomic force microscopy for probing nanoscale dynamics. NANO LETTERS 2012; 12:893-898. [PMID: 22248070 DOI: 10.1021/nl203956q] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We propose, simulate, and experimentally validate a new mechanical detection method to analyze atomic force microscopy (AFM) cantilever motion that enables noncontact discrimination of transient events with ~100 ns temporal resolution without the need for custom AFM probes, specialized instrumentation, or expensive add-on hardware. As an example application, we use the method to screen thermally annealed poly(3-hexylthiophene):phenyl-C(61)-butyric acid methyl ester photovoltaic devices under realistic testing conditions over a technologically relevant performance window. We show that variations in device efficiency and nanoscale transient charging behavior are correlated, thereby linking local dynamics with device behavior. We anticipate that this method will find application in scanning probe experiments of dynamic local mechanical, electronic, magnetic, and biophysical phenomena.
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Affiliation(s)
- Rajiv Giridharagopal
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
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100
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Slota JE, Elmalem E, Tu G, Watts B, Fang J, Oberhumer PM, Friend RH, Huck WTS. Oligomeric Compatibilizers for Control of phase Separation in Conjugated Polymer Blend Films. Macromolecules 2012. [DOI: 10.1021/ma201523m] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Joanna E. Slota
- Nanoscience
Centre, University of Cambridge, 11 JJ
Thompson Avenue, Cambridge, CB3 0FF, U.K
| | - Einat Elmalem
- Melville Laboratory for Polymer Synthesis, University of Cambridge, Lensfield Road, Cambridge,
CB2 1EW, U.K
| | - Guoli Tu
- Melville Laboratory for Polymer Synthesis, University of Cambridge, Lensfield Road, Cambridge,
CB2 1EW, U.K
- Wuhan National
Laboratory for Optoelectronics, Huazhong University of Science and Technology, 430074 Wuhan, P.R. China
| | - Benjamin Watts
- Swiss Light Source, Paul Scherrer Institut, Villigen 5232, Switzerland
| | - Junfeng Fang
- Melville Laboratory for Polymer Synthesis, University of Cambridge, Lensfield Road, Cambridge,
CB2 1EW, U.K
- Ningbo Institute of Materials
Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315211 Zhejiang, P.R. China
| | - Philipp M. Oberhumer
- Department of Physics, Cavendish Laboratory, University of Cambridge, JJ Thompson Avenue, Cambridge,
CB3 0HE, U.K
| | - Richard H. Friend
- Department of Physics, Cavendish Laboratory, University of Cambridge, JJ Thompson Avenue, Cambridge,
CB3 0HE, U.K
| | - Wilhelm T. S. Huck
- Melville Laboratory for Polymer Synthesis, University of Cambridge, Lensfield Road, Cambridge,
CB2 1EW, U.K
- Radboud University Nijmegen, Heyendaalseweg 135, 6525
AJ Nijmegen, The Netherlands
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