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Li E, Wei J, Zhang T, Wan H, Cheng Y, Xie J, Li H, Zhang K, Xu J, Hu J, Wen Q, Xiao X, Zhao T, Hu M, Su F, Wang T, Fang G. Charge Carriers Localization Effect Revealed through Terahertz Spectroscopy of MXene: Ti 3C 2T x. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2306200. [PMID: 38037679 DOI: 10.1002/smll.202306200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2023] [Revised: 11/09/2023] [Indexed: 12/02/2023]
Abstract
The transport properties of charge carriers in MXene, a promising material, have been studied using terahertz time-domain spectroscopy (THz-TDS) to examine its potential applications in optical and electronic devices. However, previous studies have been limited by narrow frequency ranges, which have hindered the understanding of the intrinsic mechanisms of carrier transport in MXenes. To address this issue, ultrabroadband THz-TDS with frequencies of up to 15 THz to investigate the complex photoconductances of MXene (Ti3C2Tx) films with different thicknesses are employed. The findings indicate that the electronic localization is substrate-dependent, and this effect decreases with an increase in the number of layers. This is attributed to the screening effect of the high carrier density in Ti3C2Tx. Additionally, the layer-independent photocarrier relaxations revealed by optical pump THz probe spectroscopy (OPTP) provide evidence of the carrier heating-induced screening effect. These results are significant for practical applications in both scientific research and various industries.
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Affiliation(s)
- Enen Li
- Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, 100094, China
- Key Laboratory of Electromagnetic Radiation and Sensing Technology, Chinese Academy of Sciences, Beijing, 100190, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
- GBA Branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou, 510700, China
- Guangdong Provincial Key Laboratory of Terahertz Quantum Electromagnetics, Guangzhou, 510700, China
| | - Jincheng Wei
- GBA Branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou, 510700, China
| | - Tianyu Zhang
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054, P. R. China
- Key Laboratory of Terahertz Technology, Ministry of Education, Chengdu, 610054, China
| | - Hujie Wan
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054, P. R. China
- Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou, Zhejiang, 313001, P. R. China
| | - Yuguang Cheng
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054, P. R. China
| | - Jiafeng Xie
- GBA Branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou, 510700, China
| | - Hong Li
- GBA Branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou, 510700, China
| | - Kai Zhang
- GBA Branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou, 510700, China
| | - Jingyin Xu
- GBA Branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou, 510700, China
| | - Jinkang Hu
- GBA Branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou, 510700, China
| | - Qiye Wen
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054, P. R. China
- Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou, Zhejiang, 313001, P. R. China
| | - Xu Xiao
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054, P. R. China
- Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou, Zhejiang, 313001, P. R. China
| | - Tao Zhao
- State Key Laboratory of Electronic Thin Film and Integrated Devices, School of Physics, University of Electronic Science and Technology of China, Chengdu, 610054, China
- Shenzhen Institute for Advanced Study, University of Electronic Science and Technology of China, Shenzhen, 518000, China
- Chengdu Research Institute, University of Electronic Science and Technology of China, Chengdu, 610207, China
| | - Min Hu
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054, P. R. China
- Key Laboratory of Terahertz Technology, Ministry of Education, Chengdu, 610054, China
| | - Fuhai Su
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei, 230031, China
| | - Tianwu Wang
- Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, 100094, China
- Key Laboratory of Electromagnetic Radiation and Sensing Technology, Chinese Academy of Sciences, Beijing, 100190, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
- GBA Branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou, 510700, China
- Guangdong Provincial Key Laboratory of Terahertz Quantum Electromagnetics, Guangzhou, 510700, China
| | - Guangyou Fang
- Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, 100094, China
- Key Laboratory of Electromagnetic Radiation and Sensing Technology, Chinese Academy of Sciences, Beijing, 100190, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
- GBA Branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou, 510700, China
- Guangdong Provincial Key Laboratory of Terahertz Quantum Electromagnetics, Guangzhou, 510700, China
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Alberding BG, Thurber WR, Heilweil EJ. Direct comparison of time-resolved Terahertz spectroscopy and Hall Van der Pauw methods for measurement of carrier conductivity and mobility in bulk semiconductors. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. B, OPTICAL PHYSICS 2017; 34:1392-1406. [PMID: 28924327 PMCID: PMC5600209 DOI: 10.1364/josab.34.001392] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Charge carrier conductivity and mobility for various semiconductor wafers and crystals were measured by ultrafast above bandgap, optically excited Time-Resolved Terahertz Spectroscopy (TRTS) and Hall Van der Pauw contact methods to directly compare these approaches and validate the use of the non-contact optical approach for future materials and in-situ device analyses. Undoped and doped silicon (Si) wafers with resistances varying over six orders of magnitude were selected as model systems since contact Hall measurements are reliably made on this material. Conductivity and mobility obtained at room temperature by terahertz transmission and TRTS methods yields the sum of electron and hole mobility which agree very well with either directly measured or literature values for corresponding atomic and photo-doping densities. Careful evaluation of the optically-generated TRTS frequency-dependent conductivity also shows it is dominated by induced free-carrier absorption rather than small probe pulse phase shifts, which is commonly ascribed to changes in the complex conductivity from sample morphology and evaluation of carrier mobility by applying Drude scattering models. Thus, in this work, the real-valued, frequency-averaged conductivity was used to extract sample mobility without application of models. Examinations of germanium (Ge), gallium arsenide (GaAs), gallium phosphide (GaP) and zinc telluride (ZnTe) samples were also made to demonstrate the general applicability of the TRTS method, even for materials that do not reliably make good contacts (e.g., GaAs, GaP, ZnTe). For these cases, values for the sum of the electron and hole mobility also compare very favorably to measured or available published data.
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Affiliation(s)
- Brian G. Alberding
- Radiation Physics Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - W. Robert Thurber
- Engineering Physics Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Edwin J. Heilweil
- Radiation Physics Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
- Corresponding author:
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Abstract
Organic (opto)electronic materials have received considerable attention due to their applications in thin-film-transistors, light-emitting diodes, solar cells, sensors, photorefractive devices, and many others. The technological promises include low cost of these materials and the possibility of their room-temperature deposition from solution on large-area and/or flexible substrates. The article reviews the current understanding of the physical mechanisms that determine the (opto)electronic properties of high-performance organic materials. The focus of the review is on photoinduced processes and on electronic properties important for optoelectronic applications relying on charge carrier photogeneration. Additionally, it highlights the capabilities of various experimental techniques for characterization of these materials, summarizes top-of-the-line device performance, and outlines recent trends in the further development of the field. The properties of materials based both on small molecules and on conjugated polymers are considered, and their applications in organic solar cells, photodetectors, and photorefractive devices are discussed.
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Affiliation(s)
- Oksana Ostroverkhova
- Department of Physics, Oregon State University , Corvallis, Oregon 97331, United States
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Alberding BG, Biacchi AJ, Walker ARH, Heilweil EJ. Charge Carrier Dynamics and Mobility Determined by Time-Resolved Terahertz Spectroscopy on Films of Nano-to-Micrometer-Sized Colloidal Tin(II) Monosulfide. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2016; 120:15395-15406. [PMID: 27766125 PMCID: PMC5066166 DOI: 10.1021/acs.jpcc.6b01684] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Tin(II) monosulfide (SnS) is a semiconductor material with an intermediate band gap, high absorption coefficient in the visible range, and earth abundant, non-toxic constituent elements. For these reasons, SnS has generated much interest for incorporation into optoelectronic devices, but little is known concerning the charge carrier dynamics, especially as measured by optical techniques. Here, as opposed to prior studies of vapor deposited films, phase-pure colloidal SnS was synthesized by solution chemistry in three size regimes, ranging from nanometer- to micron-scale (SnS small nanoparticles, SnS medium 2D nanosheets, and SnS large 2D μm-sheets), and evaluated by time-resolved terahertz spectroscopy (TRTS); an optical, non-contact probe of the photoconductivity. Dropcast films of the SnS colloids were studied by TRTS and compared to both thermally annealed films and dispersed suspensions of the same colloids. TRTS results revealed that the micron-scale SnS crystals and all of the annealed films undergo decay mechanisms during the first 200 ps following photoexcitation at 800 nm assigned to hot carrier cooling and carrier trapping. The charge carrier mobility of both the dropcast and annealed samples depends strongly on the size of the constituent colloids. The mobility of the SnS colloidal films, following the completion of the initial decays, ranged from 0.14 cm2/V·s for the smallest SnS crystals to 20.3 cm2/V·s for the largest. Annealing the colloidal films resulted in a ~ 20 % improvement in mobility for the large SnS 2D μm-sheets and a ~ 5-fold increase for the small nanoparticles and medium nanosheets.
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Affiliation(s)
- Brian G. Alberding
- Radiation Physics Division, National Institute of Standards and Technology (NIST), 100 Bureau Drive, Gaithersburg, Maryland, 20899, United States
| | - Adam J. Biacchi
- Engineering Physics Division, National Institute of Standards and Technology (NIST), 100 Bureau Drive, Gaithersburg, Maryland, 20899, United States
| | - Angela R. Hight Walker
- Engineering Physics Division, National Institute of Standards and Technology (NIST), 100 Bureau Drive, Gaithersburg, Maryland, 20899, United States
| | - Edwin J. Heilweil
- Radiation Physics Division, National Institute of Standards and Technology (NIST), 100 Bureau Drive, Gaithersburg, Maryland, 20899, United States
- (301-975-2370)
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Cunningham PD, Lane PA, Melinger JS, Esenturk O, Heilweil EJ. Probing Charge Transfer and Hot Carrier Dynamics in Organic Solar Cells with Terahertz Spectroscopy. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2016. [PMID: 28649166 DOI: 10.1117/12.2228379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Time-resolved terahertz spectroscopy (TRTS) was used to explore charge generation, transfer, and the role of hot carriers in organic solar cell materials. Two model molecular photovoltaic systems were investigated: with zinc phthalocyanine (ZnPc) or alpha-sexathiophene (α-6T) as the electron donors and buckminsterfullerene (C60) as the electron acceptor. TRTS provides charge carrier conductivity dynamics comprised of changes in both population and mobility. By using time-resolved optical spectroscopy in conjunction with TRTS, these two contributions can be disentangled. The sub-picosecond photo-induced conductivity decay dynamics of C60 were revealed to be caused by auto-ionization: the intrinsic process by which charge is generated in molecular solids. In donor-acceptor blends, the long-lived photo-induced conductivity is used for weight fraction optimization of the constituents. In nanoscale multilayer films, the photo-induced conductivity identifies optimal layer thicknesses. In films of ZnPc/C60, electron transfer from ZnPc yields hot charges that localize and become less mobile as they thermalize. Excitation of high-lying Franck Condon states in C60 followed by hole-transfer to ZnPc similarly produces hot charge carriers that self-localize; charge transfer clearly precedes carrier cooling. This picture is contrasted to charge transfer in α-6T/C60, where hole transfer takes place from a thermalized state and produces equilibrium carriers that do not show characteristic signs of cooling and self-localization. These results illustrate the value of terahertz spectroscopic methods for probing charge transfer reactions.
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Affiliation(s)
| | - Paul A Lane
- U.S. Naval Research Laboratory, Washington, DC 20375, United States
| | | | - Okan Esenturk
- Chemistry Department, Middle East Technical University, Ankara, Turkey
| | - Edwin J Heilweil
- National Institute of Standards and Technology, Gaithersburg, MD 20899, United States
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Jin Z, Gehrig D, Dyer-Smith C, Heilweil EJ, Laquai F, Bonn M, Turchinovich D. Ultrafast Terahertz Photoconductivity of Photovoltaic Polymer-Fullerene Blends: A Comparative Study Correlated with Photovoltaic Device Performance. J Phys Chem Lett 2014; 5:3662-3668. [PMID: 26278734 DOI: 10.1021/jz501890n] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Ultrafast photoinduced carrier dynamics in prototypical low band gap polymer:fullerene photovoltaic blend films PTB7:PC70BM and P3HT:PC70BM is investigated using ultrafast terahertz (THz) spectroscopy. The subpicosecond and few-picosecond decays of THz-probed photoconductivities for both compounds are observed, attributed to the rapid formation of polaron pairs by exciton-exciton annihilation and subsequent polaron pair annihilation, respectively. The transient THz photoconductivity spectra of PTB7:PC70BM are well described by the Drude-Smith (DS) model, directly yielding the important charge transport parameters such as charge carrier density, momentum scattering time, and effective localization. By comparison with P3HT:PC70BM, we find that in PTB7:PC70BM the mobile charge carrier photoconductivity is significantly enhanced by a factor of 1.8 and prevails for longer times after charge formation, due to both improved mobile charge carrier yield and lower charge localization. In PTB7:PC70BM, a strong dependency of electron momentum scattering time on electron density was found, well parametrized by the empirical Caughey-Thomas model. The difference in ultrafast photoconductivities of both P3HT:PC70BM and PTB7:PC70BM is found to correlate very well with the performance of photovoltaic devices based on those materials.
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Affiliation(s)
- Zuanming Jin
- †Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Dominik Gehrig
- †Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Clare Dyer-Smith
- †Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Edwin J Heilweil
- ‡NIST - National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - Frédéric Laquai
- †Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Mischa Bonn
- †Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Dmitry Turchinovich
- †Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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