Abstract

In condensed matter physics, quasi-particle correlations are crucial to understanding a material’s properties. For example, strong interaction between electrons with metal-like electron configuration produces strongly correlated insulators rather than conductors, which band theory would predict. Therefore, it is important to determine the interaction strength between different degrees of freedom, e.g., electron, phonon, and spin. Time-resolved spectroscopy is a powerful technique for observing energy transfer between quasi-particles and determining the interaction strength. Ultrashort-pulse light sources with extremely broadband spectra have extended exploration of ultrafast dynamics in various materials. Here, novel types of condensed-phase matter are presented to show how several key issues regarding these materials can be resolved by broadband ultrafast time-resolved spectroscopy.

© 2016 Optical Society of America

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2015 (2)

Y.-T. Wang, C.-W. Luo, A. Yabushita, K.-H. Wu, T. Kobayashi, C.-H. Chen, and L.-J. Li, “Ultrafast multi-level logic gates with spin-valley coupled polarization anisotropy in monolayer MoS2,” Sci. Rep. 5, 8289 (2015).

Y.-T. Wang, M.-H. Chen, C.-T. Lin, J.-J. Fang, C.-J. Chang, C.-W. Luo, A. Yabushita, K.-H. Wu, and T. Kobayashi, “Use of ultrafast time-resolved spectroscopy to demonstrate the effect of annealing on the performance of P3HT:PCBM solar cells,” ACS Appl. Mater. Interfaces 7, 4457–4462 (2015).
[Crossref]

2014 (5)

J. J. Fang, H. W. Tsai, I. C. Ni, S. D. Tzeng, and M. H. Chen, “The formation of interfacial wrinkles at the metal contacts on organic thin films,” Thin Solid Films 556, 294–299 (2014).
[Crossref]

D. Lagarde, L. Bouet, X. Marie, C. R. Zhu, B. L. Liu, T. Amand, P. H. Tan, and B. Urbaszek, “Carrier and polarization dynamics in monolayer MoS2,” Phys. Rev. Lett. 112, 047401 (2014).
[Crossref]

C. Mai, A. Barrette, Y. Yu, Y. G. Semenov, K. W. Kim, L. Cao, and K. Gundogdu, “Many-body effects in valleytronics: direct measurement of valley lifetimes in single layer MoS2,” Nano Lett. 14, 202–206 (2014).
[Crossref]

Y. Liu, J. Zhao, Z. Li, C. Mu, W. Ma, H. Hu, K. Jiang, H. Lin, H. Ade, and H. Yan, “Aggregation and morphology control enables multiple cases of high-efficiency polymer solar cells,” Nat. Commun. 5, 5293 (2014).
[Crossref]

C. W. Luo, P. S. Tseng, H.-J. Chen, K. H. Wu, and L. J. Li, “Dirac fermion relaxation and energy loss rate near the Fermi surface in monolayer and multilayer graphene,” Nanoscale 6, 8575–8578 (2014).
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2013 (5)

C. W. Luo, H. J. Wang, S. A. Ku, H.-J. Chen, T. T. Yeh, J.-Y. Lin, K. H. Wu, J. Y. Juang, B. L. Young, T. Kobayashi, C.-M. Cheng, C.-H. Chen, K.-D. Tsuei, R. Sankar, F. C. Chou, K. A. Kokh, O. E. Tereshchenko, E. V. Chulkov, Y. M. Andreev, and G. D. Gu, “Snapshots of Dirac fermions near the Dirac point in topological insulators,” Nano Lett. 13, 5797–5802 (2013).
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C. W. Luo, H.-J. Chen, C. M. Tu, C. C. Lee, S. A. Ku, W. Y. Tzeng, T. T. Yeh, M. C. Chiang, H. J. Wang, W. C. Chu, J.-Y. Lin, K. H. Wu, J. Y. Juang, T. Kobayashi, C.-M. Cheng, C.-H. Chen, K.-D. Tsuei, H. Berger, R. Sankar, F. C. Chou, and H. D. Yang, “THz generation and detection on Dirac fermions in topological insulators,” Adv. Opt. Mater. 1, 804–808 (2013).
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Q. Wang, S. Ge, X. Li, J. Qiu, Y. Ji, J. Feng, and D. Sun, “Valley carrier dynamics in monolayer molybdenum disulphide from helicity resolved ultrafast pump-probe spectroscopy,” ACS Nano 7, 11087–11093 (2013).
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H. Shi, R. Yan, S. Bertolazzi, J. Brivio, B. Gao, A. Kis, D. Jena, H. G. Xing, and L. Huang, “Exciton dynamics in suspended monolayer and few-layer MoS2 2D crystals,” ACS Nano 7, 1072–1080 (2013).
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W. H. Tseng, H. Lo, J. K. Chang, I. H. Liu, M. H. Chen, and C. I. Wu, “Metal-induced molecular diffusion in [6,6]-phenyl-C61-butyric acid methyl ester poly(3-hexylthiophene) based bulk-heterojunction solar cells,” Appl. Phys. Lett. 103, 183506 (2013).
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2012 (7)

K. F. Mak, K. He, J. Shan, and T. F. Heinz, “Control of valley polarization in monolayer MoS2 by optical helicity,” Nat. Nanotechnol. 7, 494–498 (2012).
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T. Stubhan, M. Salinas, A. Ebel, F. C. Krebs, A. Hirsch, M. Halik, and C. J. Brabec, “Increasing the fill factor of inverted P3HT:PCBM solar cells through surface modification of Al-doped ZnO via phosphonic acid-anchored C60 SAMs,” Adv. Energy Mater. 2, 532–535 (2012).
[Crossref]

H.-J. Chen, K. H. Wu, C. W. Luo, T. M. Uen, J. Y. Juang, J.-Y. Lin, T. Kobayashi, H. D. Yang, R. Shankar, F. C. Chou, H. Berger, and J. M. Liu, “Phonon dynamics in CuxBi2Se3 (x = 0, 0.1, 0.125) and Bi2Se2 crystals studied using femtosecond spectroscopy,” Appl. Phys. Lett. 101, 121912 (2012).
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L. Y. Chen, J. C. Yang, C. W. Luo, C. W. Liang, K. H. Wu, J.-Y. Lin, T. M. Uen, J. Y. Juang, Y. H. Chu, and T. Kobayashi, “Ultrafast photoinduced mechanical strain in epitaxial BiFeO3 thin films,” Appl. Phys. Lett. 101, 041902 (2012).
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C. W. Luo, I. H. Wu, P. C. Cheng, J.-Y. Lin, K. H. Wu, T. M. Uen, J. Y. Juang, T. Kobayashi, D. A. Chareev, O. S. Volkova, and A. N. Vasiliev, “Quasiparticle dynamics and phonon softening in FeSe superconductors,” Phys. Rev. Lett. 108, 257006 (2012).
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Q. H. Wang, K. Kalantar-Zadeh, A. Kis, J. N. Coleman, and M. S. Strano, “Electronics and optoelectronics of two-dimensional transition metal dichalcogenides,” Nat. Nanotechnol. 7, 699–712 (2012).
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Y. Nomura, H. Shirai, K. Ishii, N. Tsurumachi, A. A. Voronin, A. M. Zheltikov, and T. Fuji, “Phase-stable subcycle mid-infrared conical emission from filamentation in gases,” Opt. Express 20, 24741–24747 (2012).
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2011 (7)

C. C. Hsu, Y. T. Wang, A. Yabushita, C. W. Luo, Y. N. Hsiao, S. H. Lin, and T. Kobayashi, “Environment-dependent ultrafast photoisomerization dynamics in azo dye,” J. Phys. Chem. A 115, 11508–11514 (2011).
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Y. Kida and T. Kobayashi, “Generation of sub-10 fs ultraviolet Gaussian pulses,” J. Opt. Soc. Am. B 28, 139–148 (2011).
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K. Okamura and T. Kobayashi, “Octave-spanning carrier-envelope phase stabilized visible pulse with sub-3-fs pulse duration,” Opt. Lett. 36, 226–228 (2011).
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T. Kobayashi and A. Yabushita, “Transition-state spectroscopy using ultrashort laser pulses,” Chem. Rec. 11, 99–116 (2011).
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H. S. Shih, L. Y. Chen, C. W. Luo, K. H. Wu, J.-Y. Lin, J. Y. Juang, T. M. Uen, J. M. Lee, J. M. Chen, and T. Kobayashi, “Ultrafast thermoelastic dynamics of HoMnO3 single crystals derived from femtosecond optical pump-probe spectroscopy,” New J. Phys. 13, 053003 (2011).
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F. C. Krebs, R. Søndergaard, and M. Jørgensen, “Printed metal back electrodes for R2R fabricated polymer solar cells studied using the LBIC technique,” Sol. Energy Mater. Sol. Cells 95, 1348–1353 (2011).
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B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, “Single-layer MoS2 transistors,” Nat. Nanotechnol. 6, 147–150 (2011).
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2010 (6)

A. Yabushita, Y. H. Lee, and T. Kobayashi, “Development of a multiplex fast-scan system for ultrafast time-resolved spectroscopy,” Rev. Sci. Instrum. 81, 063110 (2010).
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K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically thin MoS2: a new direct-gap semiconductor,” Phys. Rev. Lett. 105, 136805 (2010).
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A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C.-Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2,” Nano Lett. 10, 1271–1275 (2010).
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A. Orimo, K. Masuda, S. Honda, H. Benten, S. Ito, H. Ohkita, and H. Tsuji, “Surface segregation at the aluminum interface of poly(3-hexylthiophene)/fullerene solar cells,” Appl. Phys. Lett. 96, 043305 (2010).
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Y. H. Lee, A. Yabushita, C. S. Hsu, S. H. Yang, I. Iwakura, C. W. Luo, K. H. Wu, and T. Kobayashi, “Ultrafast relaxation dynamics of photoexcitations in poly(3-hexylthiophene) for the determination of the defect concentration,” Chem. Phys. Lett. 498, 71–76 (2010).
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C. Gadermaier, A. S. Alexandrov, V. V. Kabanov, P. Kusar, T. Mertelj, X. Yao, C. Manzoni, D. Brida, G. Cerullo, and D. Mihailovic, “Electron-phonon coupling in high-temperature cuprate superconductors determined from electron relaxation rates,” Phys. Rev. Lett. 105, 257001 (2010).
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2009 (5)

C. W. Luo, Y. T. Wang, F. W. Chen, and H. C. Shih, “Eliminate coherence spike in reflection-type pump-probe measurements,” Opt. Express 17, 11321–11327 (2009).
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C. Y. Wong, J. Kim, P. S. Nair, M. C. Nagy, and G. D. Scholes, “Relaxation in the exciton fine structure of semiconductor nanocrystals,” J. Phys. Chem. C 113, 795–811 (2009).
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G. Dennler, M. C. Scharber, and C. J. Brabec, “Polymer-fullerene bulk-heterojunction solar cells,” Adv. Mater. 21, 1323–1338 (2009).
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H. J. Kim, J. H. Park, H. H. Lee, D. R. Lee, and J.-J. Kim, “The effect of Al electrodes on the nanostructure of poly(3-hexylthiophene): fullerene solar cell blends during thermal annealing,” Org. Electron. 10, 1505–1510 (2009).
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H. C. Shih, T. H. Lin, C. W. Luo, J.-Y. Lin, T. M. Uen, J. Y. Juang, K. H. Wu, J. M. Lee, J. M. Chen, and T. Kobayashi, “Magnetization dynamics and Mn3+ d-d excitation in hexagonal HoMnO3 revealed by wavelength-tunable time-resolved femtosecond spectroscopy,” Phys. Rev. B 80, 024427 (2009).
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2007 (5)

Y. Zhao, Z. Xie, Y. Qu, Y. Geng, and L. Wang, “Solvent-vapor treatment induced performance enhancement of poly(3-hexylthiophene): methanofullerene bulk-heterojunction photovoltaic cells,” Appl. Phys. Lett. 90, 043504 (2007).
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A. Rycerz, J. Tworzydlo, and C. W. J. Beenakker, “Valley filter and valley valve in graphene,” Nat. Phys. 3, 172–175 (2007).
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T. Fuji and T. Suzuki, “Generation of sub-two-cycle mid-infrared pulses by four-wave mixing through filamentation in air,” Opt. Lett. 32, 3330–3332 (2007).
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G. Cerullo, C. Manzoni, L. Lüer, and D. Polli, “Time-resolved methods in biophysics. 4. Broadband pump-probe spectroscopy system with sub-20 fs temporal resolution for the study of energy transfer processes in photosynthesis,” Photochem. Photobiol. Sci. 6, 135–144 (2007).
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T. Kobayashi, A. Yabushita, T. Saito, H. Ohtani, and M. Tsuda, “Sub-5-fs real-time spectroscopy of transition states in bacteriorhodopsin during retinal isomerization,” Photochem. Photobiol. 83, 363–369 (2007).
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2006 (4)

X. Ai, M. C. Beard, K. P. Knutsen, S. E. Shaheen, G. Rumbles, and R. J. Ellingson, “Photoinduced charge carrier generation in a poly(3-hexylthiophene) and methanofullerene bulk heterojunction investigated by time-resolved terahertz spectroscopy,” J. Phys. Chem. B 110, 25462–25471 (2006).
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C. W. Luo, C. C. Hsieh, Y.-J. Chen, P. T. Shih, M. H. Chen, K. H. Wu, J. Y. Juang, J.-Y. Lin, T. M. Uen, and Y. S. Gou, “Spatial dichotomy of quasiparticle dynamics in underdoped thin-film YBa2Cu3O7-δ superconductors,” Phys. Rev. B 74, 184525 (2006).
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P. A. Lee, N. Nagaosa, and X.-G. Wen, “Doping a Mott insulator: physics of high-temperature superconductivity,” Rev. Mod. Phys. 78, 17–85 (2006).
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W. Eerenstein, N. D. Mathur, and J. F. Scott, “Multiferroic and magnetoelectric materials,” Nature 442, 759–765 (2006).
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2005 (2)

C. W. Luo, P. T. Shih, Y.-J. Chen, M. H. Chen, K. H. Wu, J. Y. Juang, J.-Y. Lin, T. M. Uen, and Y. S. Gou, “Spatially resolved relaxation dynamics of photoinduced quasiparticle in underdoped YBa2Cu3O7-δ,” Phys. Rev. B 72, 092506 (2005).
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V. Shrotriya, J. Ouyang, R. J. Tseng, G. Li, and Y. Yang, “Absorption spectra modification in poly(3-hexylthiophene): methanofullerene blend thin films,” Chem. Phys. Lett. 411, 138–143 (2005).
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2004 (4)

C. Winder and N. S. Sariciftci, “Low bandgap polymers for photon harvesting in bulk heterojunction solar cells,” J. Mater. Chem. 14, 1077–1086 (2004).
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T. J. Savenije, J. E. Kroeze, M. M. Wienk, J. M. Kroon, and J. W. Warman, “Mobility and decay kinetics of charge carriers in photoexcited PCBM/PPV blends,” Phys. Rev. B 69, 155205 (2004).
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I. Zutic, J. Fabian, and S. Das Sarma, “Spintronics: fundamentals and applications,” Rev. Mod. Phys. 76, 323–410 (2004).
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C. W. Luo, K. Reimann, M. Woerner, T. Elsaesser, R. Hey, and K. H. Ploog, “Phase-resolved nonlinear response of a two-dimensional electron gas under femtosecond intersubband excitation,” Phys. Rev. Lett. 92, 047402 (2004).
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2003 (1)

C. W. Luo, M. H. Chen, S. P. Chen, K. H. Wu, J. Y. Juang, J.-Y. Lin, T. M. Uen, and Y. S. Gou, “Spatial symmetry of superconducting gap in YBa2Cu3O7-δ obtained from femtosecond spectroscopy,” Phys. Rev. B 68, 220508 (2003).
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2002 (1)

T. Kobayashi and A. Baltuška, “Sub-5 fs pulse generation from a noncollinear optical parametric amplifier,” Meas. Sci. Technol. 13, 1671–1682 (2002).
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2001 (1)

C. J. Brabec, G. Zerza, G. Cerullo, S. De Silvestri, S. Luzzati, J. C. Hummelen, and S. Sariciftci, “Tracing photoinduced electron transfer process in conjugated polymer/fullerene bulk heterojunctions in real time,” Chem. Phys. Lett. 340, 232–236 (2001).
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2000 (1)

T. Kobayashi and A. Shirakawa, “Tunable visible and near-infrared pulse generator in a 5 fs regime,” Appl. Phys. B 70, S239–S246 (2000).
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1999 (1)

A. Shirakawa, I. Sakane, M. Takasaka, and T. Kobayashi, “Sub-5-fs visible pulse generation by pulse-front-matched noncollinear optical parametric amplification,” Appl. Phys. Lett. 74, 2268–2270 (1999).
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1998 (3)

1997 (2)

1996 (1)

M. K. Reed and M. K. S. Shepard, “Tunable infrared generation using a femtosecond 250 kHz Ti:sapphire regenerative amplifier,” IEEE J. Quantum Electron. 32, 1273–1277 (1996).
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1995 (2)

1994 (2)

V. Petrov, F. Seifert, O. Kittelmann, J. Ringling, and F. Noack, “Extension of the tuning range of a femtosecond Ti:sapphire laser amplifier through cascaded second-order nonlinear frequency conversion processes,” J. Appl. Phys. 76, 7704–7712 (1994).
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H. V. Löhneysen, T. Pietrus, G. Portisch, H. G. Schlager, A. Schröder, M. Sieck, and T. Trappmann, “Non-Fermi-liquid behavior in a heavy-fermion alloy at a magnetic instability,” Phys. Rev. Lett. 72, 3262–3265 (1994).
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1993 (1)

1992 (1)

J. B. Stark, W. H. Knox, and D. S. Chemla, “Spin-resolved femtosecond magnetoexciton interactions in GaAs quantum wells,” Phys. Rev. B 46, 7919–7922 (1992).
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1991 (2)

1990 (1)

C. J. Stanton, D. W. Bailey, and K. Hess, “Femtosecond-pump, continuum-probe nonlinear absorption in GaAs,” Phys. Rev. Lett. 65, 231–234 (1990).
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1987 (1)

R. W. Schoenlein, W. Z. Lin, E. P. Ippen, and J. G. Fujimoto, “Femtosecond hot-carrier energy relaxation in GaAs,” Appl. Phys. Lett. 51, 1442–1445 (1987).
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1986 (1)

C. W. Tang, “Two-layer organic photovoltaic cell,” Appl. Phys. Lett. 48, 183–185 (1986).
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1979 (1)

C. V. Shank, R. L. Fork, R. F. Leheny, and J. Shah, “Dynamics of photoexcited GaAs band-edge absorption with subpicosecond resolution,” Phys. Rev. Lett. 42, 112–115 (1979).
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1978 (1)

C. Lin, V. T. Nguyen, and W. G. French, “Wideband near-I.R. continuum (0.7–2.1 μm) generated in low-loss optical fibres,” Electron. Lett. 14, 822–823 (1978).
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C. Lin and R. H. Stolen, “New nanosecond continuum for excited-state spectroscopy,” Appl. Phys. Lett. 28, 216–218 (1976).
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1974 (1)

D. Magde and M. W. Windsor, “Picosecond flash photolysis and spectroscopy: 3, 3’-diethyloxadicarbocyanine iodide (DODCI),” Chem. Phys. Lett. 27, 31–36 (1974).
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1971 (2)

M. R. Topp, P. M. Rentzepis, and R. P. Jones, “Time resolved picosecond emission spectroscopy of organic dye lasers,” Chem. Phys. Lett. 9, 1–5 (1971).
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H. Heinrich and W. Jantsch, “Experimental determination of the electron temperature from Burstein-shift experiments in gallium antimonide,” Phys. Rev. B 4, 2504–2508 (1971).
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T. R. Hart, R. L. Aggarwal, and B. Lax, “Temperature dependence of Raman scattering in silicon,” Phys. Rev. B 1, 638–642 (1970).
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R. R. Alfano and S. L. Shapiro, “Emission in the region 4000 to 7000 Å via four-photon coupling in glass,” Phys. Rev. Lett. 24, 584–587 (1970).
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R. R. Alfano and S. L. Shapiro, “Direct distortion of electronic clouds of rare-gas atoms in intense electric fields,” Phys. Rev. Lett. 24, 1217–1220 (1970).
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1968 (1)

D. Adler, “Mechanisms for metal-nonmetal transitions in transition-metal oxides and sulfides,” Rev. Mod. Phys. 40, 714–736 (1968).
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1966 (1)

K. F. Komatsubara, “Effect of electric field on the transverse magnetoresistance in n-indium antimonide at 1.5 K,” Phys. Rev. Lett. 16, 1044–1047 (1966).
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1964 (2)

J. Zucker, “Thermoelectric power of hot carriers,” J. Appl. Phys. 35, 618–621 (1964).
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1951 (1)

J. R. Haynes and W. Shockley, “The mobility and life of injected holes and electrons in germanium,” Phys. Rev. 81, 835–843 (1951).
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Ade, H.

Y. Liu, J. Zhao, Z. Li, C. Mu, W. Ma, H. Hu, K. Jiang, H. Lin, H. Ade, and H. Yan, “Aggregation and morphology control enables multiple cases of high-efficiency polymer solar cells,” Nat. Commun. 5, 5293 (2014).
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Adler, D.

D. Adler, “Mechanisms for metal-nonmetal transitions in transition-metal oxides and sulfides,” Rev. Mod. Phys. 40, 714–736 (1968).
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Aggarwal, R. L.

T. R. Hart, R. L. Aggarwal, and B. Lax, “Temperature dependence of Raman scattering in silicon,” Phys. Rev. B 1, 638–642 (1970).
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Ai, X.

X. Ai, M. C. Beard, K. P. Knutsen, S. E. Shaheen, G. Rumbles, and R. J. Ellingson, “Photoinduced charge carrier generation in a poly(3-hexylthiophene) and methanofullerene bulk heterojunction investigated by time-resolved terahertz spectroscopy,” J. Phys. Chem. B 110, 25462–25471 (2006).
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Alexandrov, A. S.

C. Gadermaier, A. S. Alexandrov, V. V. Kabanov, P. Kusar, T. Mertelj, X. Yao, C. Manzoni, D. Brida, G. Cerullo, and D. Mihailovic, “Electron-phonon coupling in high-temperature cuprate superconductors determined from electron relaxation rates,” Phys. Rev. Lett. 105, 257001 (2010).
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Alfano, R. R.

R. R. Alfano and S. L. Shapiro, “Direct distortion of electronic clouds of rare-gas atoms in intense electric fields,” Phys. Rev. Lett. 24, 1217–1220 (1970).
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R. R. Alfano and S. L. Shapiro, “Observation of self-modulation and small-scale filaments in crystals and glasses,” Phys. Rev. Lett. 24, 592–594 (1970).
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R. R. Alfano and S. L. Shapiro, “Emission in the region 4000 to 7000 Å via four-photon coupling in glass,” Phys. Rev. Lett. 24, 584–587 (1970).
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Amand, T.

D. Lagarde, L. Bouet, X. Marie, C. R. Zhu, B. L. Liu, T. Amand, P. H. Tan, and B. Urbaszek, “Carrier and polarization dynamics in monolayer MoS2,” Phys. Rev. Lett. 112, 047401 (2014).
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Andreev, Y. M.

C. W. Luo, H. J. Wang, S. A. Ku, H.-J. Chen, T. T. Yeh, J.-Y. Lin, K. H. Wu, J. Y. Juang, B. L. Young, T. Kobayashi, C.-M. Cheng, C.-H. Chen, K.-D. Tsuei, R. Sankar, F. C. Chou, K. A. Kokh, O. E. Tereshchenko, E. V. Chulkov, Y. M. Andreev, and G. D. Gu, “Snapshots of Dirac fermions near the Dirac point in topological insulators,” Nano Lett. 13, 5797–5802 (2013).
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C. J. Stanton, D. W. Bailey, and K. Hess, “Femtosecond-pump, continuum-probe nonlinear absorption in GaAs,” Phys. Rev. Lett. 65, 231–234 (1990).
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Baltuška, A.

T. Kobayashi and A. Baltuška, “Sub-5 fs pulse generation from a noncollinear optical parametric amplifier,” Meas. Sci. Technol. 13, 1671–1682 (2002).
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C. Mai, A. Barrette, Y. Yu, Y. G. Semenov, K. W. Kim, L. Cao, and K. Gundogdu, “Many-body effects in valleytronics: direct measurement of valley lifetimes in single layer MoS2,” Nano Lett. 14, 202–206 (2014).
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X. Ai, M. C. Beard, K. P. Knutsen, S. E. Shaheen, G. Rumbles, and R. J. Ellingson, “Photoinduced charge carrier generation in a poly(3-hexylthiophene) and methanofullerene bulk heterojunction investigated by time-resolved terahertz spectroscopy,” J. Phys. Chem. B 110, 25462–25471 (2006).
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Beenakker, C. W. J.

A. Rycerz, J. Tworzydlo, and C. W. J. Beenakker, “Valley filter and valley valve in graphene,” Nat. Phys. 3, 172–175 (2007).
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Benten, H.

A. Orimo, K. Masuda, S. Honda, H. Benten, S. Ito, H. Ohkita, and H. Tsuji, “Surface segregation at the aluminum interface of poly(3-hexylthiophene)/fullerene solar cells,” Appl. Phys. Lett. 96, 043305 (2010).
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C. W. Luo, H.-J. Chen, C. M. Tu, C. C. Lee, S. A. Ku, W. Y. Tzeng, T. T. Yeh, M. C. Chiang, H. J. Wang, W. C. Chu, J.-Y. Lin, K. H. Wu, J. Y. Juang, T. Kobayashi, C.-M. Cheng, C.-H. Chen, K.-D. Tsuei, H. Berger, R. Sankar, F. C. Chou, and H. D. Yang, “THz generation and detection on Dirac fermions in topological insulators,” Adv. Opt. Mater. 1, 804–808 (2013).
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H.-J. Chen, K. H. Wu, C. W. Luo, T. M. Uen, J. Y. Juang, J.-Y. Lin, T. Kobayashi, H. D. Yang, R. Shankar, F. C. Chou, H. Berger, and J. M. Liu, “Phonon dynamics in CuxBi2Se3 (x = 0, 0.1, 0.125) and Bi2Se2 crystals studied using femtosecond spectroscopy,” Appl. Phys. Lett. 101, 121912 (2012).
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H. Shi, R. Yan, S. Bertolazzi, J. Brivio, B. Gao, A. Kis, D. Jena, H. G. Xing, and L. Huang, “Exciton dynamics in suspended monolayer and few-layer MoS2 2D crystals,” ACS Nano 7, 1072–1080 (2013).
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D. Lagarde, L. Bouet, X. Marie, C. R. Zhu, B. L. Liu, T. Amand, P. H. Tan, and B. Urbaszek, “Carrier and polarization dynamics in monolayer MoS2,” Phys. Rev. Lett. 112, 047401 (2014).
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Brabec, C. J.

T. Stubhan, M. Salinas, A. Ebel, F. C. Krebs, A. Hirsch, M. Halik, and C. J. Brabec, “Increasing the fill factor of inverted P3HT:PCBM solar cells through surface modification of Al-doped ZnO via phosphonic acid-anchored C60 SAMs,” Adv. Energy Mater. 2, 532–535 (2012).
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G. Dennler, M. C. Scharber, and C. J. Brabec, “Polymer-fullerene bulk-heterojunction solar cells,” Adv. Mater. 21, 1323–1338 (2009).
[Crossref]

C. J. Brabec, G. Zerza, G. Cerullo, S. De Silvestri, S. Luzzati, J. C. Hummelen, and S. Sariciftci, “Tracing photoinduced electron transfer process in conjugated polymer/fullerene bulk heterojunctions in real time,” Chem. Phys. Lett. 340, 232–236 (2001).
[Crossref]

Brida, D.

C. Gadermaier, A. S. Alexandrov, V. V. Kabanov, P. Kusar, T. Mertelj, X. Yao, C. Manzoni, D. Brida, G. Cerullo, and D. Mihailovic, “Electron-phonon coupling in high-temperature cuprate superconductors determined from electron relaxation rates,” Phys. Rev. Lett. 105, 257001 (2010).
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Y.-T. Wang, C.-W. Luo, A. Yabushita, K.-H. Wu, T. Kobayashi, C.-H. Chen, and L.-J. Li, “Ultrafast multi-level logic gates with spin-valley coupled polarization anisotropy in monolayer MoS2,” Sci. Rep. 5, 8289 (2015).

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C. C. Hsu, Y. T. Wang, A. Yabushita, C. W. Luo, Y. N. Hsiao, S. H. Lin, and T. Kobayashi, “Environment-dependent ultrafast photoisomerization dynamics in azo dye,” J. Phys. Chem. A 115, 11508–11514 (2011).
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ACS Appl. Mater. Interfaces (1)

Y.-T. Wang, M.-H. Chen, C.-T. Lin, J.-J. Fang, C.-J. Chang, C.-W. Luo, A. Yabushita, K.-H. Wu, and T. Kobayashi, “Use of ultrafast time-resolved spectroscopy to demonstrate the effect of annealing on the performance of P3HT:PCBM solar cells,” ACS Appl. Mater. Interfaces 7, 4457–4462 (2015).
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ACS Nano (2)

Q. Wang, S. Ge, X. Li, J. Qiu, Y. Ji, J. Feng, and D. Sun, “Valley carrier dynamics in monolayer molybdenum disulphide from helicity resolved ultrafast pump-probe spectroscopy,” ACS Nano 7, 11087–11093 (2013).
[Crossref]

H. Shi, R. Yan, S. Bertolazzi, J. Brivio, B. Gao, A. Kis, D. Jena, H. G. Xing, and L. Huang, “Exciton dynamics in suspended monolayer and few-layer MoS2 2D crystals,” ACS Nano 7, 1072–1080 (2013).
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Adv. Energy Mater. (1)

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Adv. Mater. (1)

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Supplementary Material (1)

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Figures (13)

Fig. 1.
Fig. 1.

Schematic representation of a system including electron, phonon, and spin degrees of freedom.

Fig. 2.
Fig. 2.

Schematic diagram of BBO-based OPA. The OPA was pumped by 400 nm pulses, and its tunable range is 480–700 nm with a pulse duration of 35 fs. Inset: normalized output spectra of the wavelength-tunable OPA, ranging from 500 to 700 nm.

Fig. 3.
Fig. 3.

(a) Broadband OPA output spectrum, which covers almost the entire visible range. (b) Measured second-harmonic generation frequency-resolved optical gating (SHG FROG) trace of the output broadband OPA pulses.

Fig. 4.
Fig. 4.

(a) Schematic diagram of the pump–probe technique. Time delay (Δt) between pump and probe pulses can be controlled by a mechanical delay line. (b) Fundamental principle of pump–probe spectroscopy. Time-dependent refractive index changes n(t) of the sample induced by pump pulses can be observed by detecting the intensity variations of probe pulses.

Fig. 5.
Fig. 5.

Schematic diagram of the multichannel lock-in amplifier for the broadband pump–probe measurement system. APDs, avalanche photodiodes.

Fig. 6.
Fig. 6.

Spectra of 1.89 eV pump pulse (red), 2.01 eV pump pulse (orange), broadband visible probe pulse (gray), and the stationary absorption of monolayer MoS2 at room temperature (blue). Inset: lattice structure of MoS2 in out-of-plane direction. Adapted from [72].

Fig. 7.
Fig. 7.

(a) Transient absorbance difference (ΔA) induced by excitation using σ+ circularly polarized pump pulses with a photon energy of 1.89 eV and probed by σ+ circularly polarized pulses at 78 K. Black curves are contours for ΔA=zero. Red line indicates expected values of transition A as a function of the time delays and probe photon energies. (b) Probe delay time traces of ΔA at various probe photon energies. Red and blue lines represent σ+ and σ probes, respectively, and horizontal green lines show ΔA=0. Adapted from [72].

Fig. 8.
Fig. 8.

Triple exponential fitting results of time-resolved ΔA data excited by 2.01 eV and σ+ pump pulse at 78 K. Left column, σ+ probe; right column, σ probe. (a) ΔA spectra, (b) time constant of each component. Dotted lines indicate estimated values. Adapted from [72].

Fig. 9.
Fig. 9.

Schematic diagram of the relaxation processes in monolayer MoS2. Adapted from [72].

Fig. 10.
Fig. 10.

Current density–voltage (J-V) characteristics of solar cells of ITO/PEDOT:PSS/P3HT:PCBM/Al with pre- and post-annealing processes. Inset: device architecture of a bulk heterojunction solar cell device. The Al layer is the cathode. The active layer is a semiconducting polymer/fullerene blend. ITO coated with PEDOT:PSS serves as the anode. These layers are deposited on a glass substrate. Adapted with permission from [86]. Copyright (2015) American Chemical Society.

Fig. 11.
Fig. 11.

(a), (c) Two-dimensional plots of transient absorption difference ΔA(ω,t). (b), (d) ΔA(ω) spectra at various time delays for preannealed and post-annealed P3HT:PCBM devices in (a) and (c), respectively. Adapted with permission from [86]. Copyright (2015) American Chemical Society.

Fig. 12.
Fig. 12.

Schematic representation of ultrafast carrier dynamics after photoexcitation. ELUMOD, the LUMO of the electron donor; EHOMOD, the highest occupied molecular orbital (HOMO) of the electron donor; ELUMOA, the LUMO of the electron acceptor; EHOMOA, the HOMO of the electron acceptor. In this study, the electron donor and electron acceptor are P3HT and PCBM, respectively. τ is the time constant for the relaxation processes. Adapted with permission from [86]. Copyright (2015) American Chemical Society.

Fig. 13.
Fig. 13.

Average percentages of each of the relaxation processes shown in Fig. 12 at 1.98–2.13 eV. Adapted with permission from [86]. Copyright (2015) American Chemical Society.

Equations (5)

Equations on this page are rendered with MathJax. Learn more.

A=log10(I0RT).
A=log10(I0(R+ΔR)T+ΔT),
ΔA=log10(I0(R+ΔR)T+ΔT)log10(I0RT)=log10I0(R+ΔR)(1+ΔTT)(I0R).
ΔA(ω,t)=ΔAspin(ω)etτspin+ΔAexciton(ω)etτexciton+ΔAcarrier(ω)etτcarrier+ΔAeh(ω).
ΔA(t)=ACTetτCT+ASP(etτCT+etτSP)+Atrap(etτCT+etτtrap)+ARecomb,

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