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Caballero-Quintana I, Amargós-Reyes O, Maldonado JL, Nicasio-Collazo J, Romero-Borja D, Barreiro-Argüelles D, Molnár G, Bousseksou A. Scanning Probe Microscopy Analysis of Nonfullerene Organic Solar Cells. ACS APPLIED MATERIALS & INTERFACES 2020; 12:29520-29527. [PMID: 32466653 DOI: 10.1021/acsami.0c06048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In this work, scanning probe microscopies (SPMs) are used for the analysis of PBDB-T, ITIC, and PBDB-T:ITIC layers of solar cells (OSCs). Scanning tunneling microscopy (STM) images of PBDB-T reveal that thin films (<1 nm) tend to form worm-like pattern (amorphous type) domains with an average chain-to-chain distance of 950 pm; likewise, STM images of ITIC show that side arms form chain-like patterns. STM images of PBDB-T:ITIC blend suggest why PBDB-T domains could facilitate charge dissociation. Further, a strong interchain π-π interaction of the ITIC molecules could promote self-organization, and under the mutual interaction with the PBDB-T polymer, it could influence the pathway formation for electron transport. Moreover, when correlating electrostatic force microscopy (EFM) and photoconductive atomic force microscopy (pc-AFM), the blend morphology and its electrical/electronic properties are determined; the ideal domain size of PBDB-T:ITIC blend phases for maximizing the generated photocurrent is 15-35 nm. Furthermore, phase contrast and surface electric potential characteristics with Kelvin probe force microscopy (KPFM) are measured to examine additional details about the surface and potential changes due to the domain differences in the active layer. OSCs based on the nonfullerene PBDB-T:ITIC active layer reach an average power conversion efficiency (PCE) of 9.1% (best 9.2%).
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Affiliation(s)
- Irving Caballero-Quintana
- Research Group of Optical Properties of Materials (GPOM), Centro de Investigaciones en Óptica, A.P. 1-948, 37150 León, Guanajuato, México
| | - Olivia Amargós-Reyes
- Research Group of Optical Properties of Materials (GPOM), Centro de Investigaciones en Óptica, A.P. 1-948, 37150 León, Guanajuato, México
| | - José-Luis Maldonado
- Research Group of Optical Properties of Materials (GPOM), Centro de Investigaciones en Óptica, A.P. 1-948, 37150 León, Guanajuato, México
| | - Juan Nicasio-Collazo
- Research Group of Optical Properties of Materials (GPOM), Centro de Investigaciones en Óptica, A.P. 1-948, 37150 León, Guanajuato, México
| | - Daniel Romero-Borja
- Research Group of Optical Properties of Materials (GPOM), Centro de Investigaciones en Óptica, A.P. 1-948, 37150 León, Guanajuato, México
| | - Denisse Barreiro-Argüelles
- Research Group of Optical Properties of Materials (GPOM), Centro de Investigaciones en Óptica, A.P. 1-948, 37150 León, Guanajuato, México
- Laboratorio de Fisicoquı́mica y Reactividad de Superficies (LaFReS), Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México (UNAM), CU, Coyoacán, 04510, Ciudad de México, México
| | - Gábor Molnár
- LCC, CNRS & University of Toulouse, 205 Route de Narbonne, BP44099, 31077 Toulouse Cedex 4, France
| | - Azzedine Bousseksou
- LCC, CNRS & University of Toulouse, 205 Route de Narbonne, BP44099, 31077 Toulouse Cedex 4, France
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Uluutku B, Solares SD. Current measurements in the intermittent-contact mode of atomic force microscopy using the Fourier method: a feasibility analysis. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2020; 11:453-465. [PMID: 32215233 PMCID: PMC7082697 DOI: 10.3762/bjnano.11.37] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 02/22/2020] [Indexed: 06/10/2023]
Abstract
Atomic force microscopy (AFM) is an important tool for measuring a variety of nanoscale surface properties, such as topography, viscoelasticity, electrical potential and conductivity. Some of these properties are measured using contact methods (static contact or intermittent contact), while others are measured using noncontact methods. Some properties can be measured using different approaches. Conductivity, in particular, is mapped using the contact-mode method. However, this modality can be destructive to delicate samples, since it involves continuously dragging the cantilever tip on the surface during the raster scan, while a constant tip-sample force is applied. In this paper we discuss a possible approach to develop an intermittent-contact conductive AFM mode based on Fourier analysis, whereby the measured current response consists of higher harmonics of the cantilever oscillation frequency. Such an approach may enable the characterization of soft samples with less damage than contact-mode imaging. To explore its feasibility, we derive the analytical form of the tip-sample current that would be obtained for attractive (noncontact) and repulsive (intermittent-contact) dynamic AFM characterization, and compare it with results obtained from numerical simulations. Although significant instrumentation challenges are anticipated, the modelling results are promising and suggest that Fourier-based higher-harmonics current measurement may enable the development of a reliable intermittent-contact conductive AFM method.
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Affiliation(s)
- Berkin Uluutku
- The George Washington University, Department of Mechanical and Aerospace Engineering, 800 22nd St. NW, Suite 3000, Washington, DC 20052, USA
| | - Santiago D Solares
- The George Washington University, Department of Mechanical and Aerospace Engineering, 800 22nd St. NW, Suite 3000, Washington, DC 20052, USA
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López-Guerra EA, Banfi F, Solares SD, Ferrini G. Theory of Single-Impact Atomic Force Spectroscopy in liquids with material contrast. Sci Rep 2018; 8:7534. [PMID: 29760518 PMCID: PMC5951954 DOI: 10.1038/s41598-018-25828-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 04/25/2018] [Indexed: 11/09/2022] Open
Abstract
Scanning probe microscopy has enabled nanoscale mapping of mechanical properties in important technological materials, such as tissues, biomaterials, polymers, nanointerfaces of composite materials, to name only a few. To improve and widen the measurement of nanoscale mechanical properties, a number of methods have been proposed to overcome the widely used force-displacement mode, that is inherently slow and limited to a quasi-static regime, mainly using multiple sinusoidal excitations of the sample base or of the cantilever. Here, a different approach is put forward. It exploits the unique capabilities of the wavelet transform analysis to harness the information encoded in a short duration spectroscopy experiment. It is based on an impulsive excitation of the cantilever and a single impact of the tip with the sample. It performs well in highly damped environments, which are often seen as problematic in other standard dynamic methods. Our results are very promising in terms of viscoelastic property discrimination. Their potential is oriented (but not limited) to samples that demand imaging in liquid native environments and also to highly vulnerable samples whose compositional mapping cannot be obtained through standard tapping imaging techniques.
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Affiliation(s)
- Enrique A López-Guerra
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, 20052, USA
| | - Francesco Banfi
- Interdisciplinary Laboratories for Advanced Materials Physics, Università Cattolica del Sacro Cuore, I-25121, Brescia, Italy.,Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121, Brescia, Italy
| | - Santiago D Solares
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, 20052, USA
| | - Gabriele Ferrini
- Interdisciplinary Laboratories for Advanced Materials Physics, Università Cattolica del Sacro Cuore, I-25121, Brescia, Italy. .,Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121, Brescia, Italy.
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Zhang W, Chen Y, Xia X, Chu J. Material discrimination and mixture ratio estimation in nanocomposites via harmonic atomic force microscopy. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2017; 8:2771-2780. [PMID: 29354348 PMCID: PMC5753115 DOI: 10.3762/bjnano.8.276] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 11/14/2017] [Indexed: 06/07/2023]
Abstract
Harmonic atomic force microscopy (AFM) was employed to discriminate between different materials and to estimate the mixture ratio of the constituent components in nanocomposites. The major influencing factors, namely amplitude feedback set-point, drive frequency and laser spot position along the cantilever beam, were systematically investigated. Employing different set-points induces alternation of tip-sample interaction forces and thus different harmonic responses. The numerical simulations of the cantilever dynamics were well-correlated with the experimental observations. Owing to the deviation of the drive frequency from the fundamental resonance, harmonic amplitude contrast reversal may occur. It was also found that the laser spot position affects the harmonic signal strengths as expected. Based on these investigations, harmonic AFM was employed to identify material components and estimate the mixture ratio in multicomponent materials. The composite samples are composed of different kinds of nanoparticles with almost the same shape and size. Higher harmonic imaging offers better information on the distribution and mixture of different nanoparticles as compared to other techniques, including topography and conventional tapping phase. Therefore, harmonic AFM has potential applications in various fields of nanoscience and nanotechnology.
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Affiliation(s)
- Weijie Zhang
- Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230026, China
| | - Yuhang Chen
- Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230026, China
| | - Xicheng Xia
- Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230026, China
| | - Jiaru Chu
- Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230026, China
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López-Guerra EA, Solares SD. Material property analytical relations for the case of an AFM probe tapping a viscoelastic surface containing multiple characteristic times. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2017; 8:2230-2244. [PMID: 29114450 PMCID: PMC5669240 DOI: 10.3762/bjnano.8.223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 09/22/2017] [Indexed: 05/22/2023]
Abstract
We explore the contact problem of a flat-end indenter penetrating intermittently a generalized viscoelastic surface, containing multiple characteristic times. This problem is especially relevant for nanoprobing of viscoelastic surfaces with the highly popular tapping-mode AFM imaging technique. By focusing on the material perspective and employing a rigorous rheological approach, we deliver analytical closed-form solutions that provide physical insight into the viscoelastic sources of repulsive forces, tip-sample dissipation and virial of the interaction. We also offer a systematic comparison to the well-established standard harmonic excitation, which is the case relevant for dynamic mechanical analysis (DMA) and for AFM techniques where tip-sample sinusoidal interaction is permanent. This comparison highlights the substantial complexity added by the intermittent-contact nature of the interaction, which precludes the derivation of straightforward equations as is the case for the well-known harmonic excitations. The derivations offered have been thoroughly validated through numerical simulations. Despite the complexities inherent to the intermittent-contact nature of the technique, the analytical findings highlight the potential feasibility of extracting meaningful viscoelastic properties with this imaging method.
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Affiliation(s)
- Enrique A López-Guerra
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA
| | - Santiago D Solares
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA
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