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Gao L, Hu Z, Lu J, Liu H, Ni Z. Defect-related dynamics of photoexcited carriers in 2D transition metal dichalcogenides. Phys Chem Chem Phys 2021; 23:8222-8235. [PMID: 33875990 DOI: 10.1039/d1cp00006c] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two-dimensional (2D) transition metal dichalcogenides (TMDs) exhibit enormous potential in the field of optoelectronics. The high performance of TMD materials and optoelectronic devices significantly depends on processes involved in photoelectric conversion, including photo-excitation, relaxation, transportation, and recombination. Remarkably, inevitable defects in materials prolong or shorten the characteristic time of these processes and even bring about new photoelectric conversion channels, namely, the defect-related relaxation pathways of photoexcited carriers tailor the performance of photoelectric applications. In recent years, there have been numerous investigations in exploring the variant transient signals caused by defects in TMDs utilizing ultrafast spectroscopies. They have the capability in providing an accurate and overall representation of ultrafast processes owing to the subtle temporal resolution. The defect-related mechanisms occurring in different time scales (from femtosecond (fs) to microsecond (μs)) play influential roles throughout the relaxation process of photoexcited species. Herein, we review the defect-related relaxation mechanisms of photoexcited species in TMDs according to the time scale utilizing ultrafast spectroscopy techniques. By interpreting and summarizing the defect-related transient signals, we furnish the direction in material design and performance optimization.
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Affiliation(s)
- Lei Gao
- School of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189, China.
| | - Zhenliang Hu
- School of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189, China.
| | - Junpeng Lu
- School of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189, China.
| | - Hongwei Liu
- Jiangsu Key Lab on Opto-Electronic Technology, School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China
| | - Zhenhua Ni
- School of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189, China.
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2
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Affiliation(s)
- Christopher Melnychuk
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
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3
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Harris RD, Bettis Homan S, Kodaimati M, He C, Nepomnyashchii AB, Swenson NK, Lian S, Calzada R, Weiss EA. Electronic Processes within Quantum Dot-Molecule Complexes. Chem Rev 2016; 116:12865-12919. [PMID: 27499491 DOI: 10.1021/acs.chemrev.6b00102] [Citation(s) in RCA: 171] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The subject of this review is the colloidal quantum dot (QD) and specifically the interaction of the QD with proximate molecules. It covers various functions of these molecules, including (i) ligands for the QDs, coupled electronically or vibrationally to localized surface states or to the delocalized states of the QD core, (ii) energy or electron donors or acceptors for the QDs, and (iii) structural components of QD assemblies that dictate QD-QD or QD-molecule interactions. Research on interactions of ligands with colloidal QDs has revealed that ligands determine not only the excited state dynamics of the QD but also, in some cases, its ground state electronic structure. Specifically, the article discusses (i) measurement of the electronic structure of colloidal QDs and the influence of their surface chemistry, in particular, dipolar ligands and exciton-delocalizing ligands, on their electronic energies; (ii) the role of molecules in interfacial electron and energy transfer processes involving QDs, including electron-to-vibrational energy transfer and the use of the ligand shell of a QD as a semipermeable membrane that gates its redox activity; and (iii) a particular application of colloidal QDs, photoredox catalysis, which exploits the combination of the electronic structure of the QD core and the chemistry at its surface to use the energy of the QD excited state to drive chemical reactions.
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Affiliation(s)
- Rachel D Harris
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Stephanie Bettis Homan
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Mohamad Kodaimati
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Chen He
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | | | - Nathaniel K Swenson
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Shichen Lian
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Raul Calzada
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Emily A Weiss
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
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4
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Ganguly J, Ghosh M. Coupled influence of noise and damped propagation of impurity on linear and nonlinear polarizabilities of doped quantum dots. Chem Phys 2015. [DOI: 10.1016/j.chemphys.2014.12.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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5
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Bhadrachalam P, Subramanian R, Ray V, Ma LC, Wang W, Kim J, Cho K, Koh SJ. Energy-filtered cold electron transport at room temperature. Nat Commun 2014; 5:4745. [PMID: 25204839 PMCID: PMC4175579 DOI: 10.1038/ncomms5745] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 07/18/2014] [Indexed: 11/25/2022] Open
Abstract
Fermi-Dirac electron thermal excitation is an intrinsic phenomenon that limits
functionality of various electron systems. Efforts to manipulate electron thermal
excitation have been successful when the entire system is cooled to cryogenic
temperatures, typically <1 K. Here we show that electron thermal
excitation can be effectively suppressed at room temperature, and energy-suppressed
electrons, whose energy distribution corresponds to an effective electron
temperature of ~45 K, can be transported throughout device
components without external cooling. This is accomplished using a discrete level of
a quantum well, which filters out thermally excited electrons and permits only
energy-suppressed electrons to participate in electron transport. The quantum well
(~2 nm of Cr2O3) is formed between source
(Cr) and tunnelling barrier
(SiO2) in a
double-barrier-tunnelling-junction structure having a quantum dot as the central
island. Cold electron transport is detected from extremely narrow differential
conductance peaks in electron tunnelling through CdSe quantum dots, with full widths at half maximum of only
~15 mV at room temperature. Electrons can behave as if they are at a temperature different from
that of the solid in which they are embedded. Here, the authors demonstrate a room
temperature device that can generate electrons with an effective temperature of
45 K by using quantum wells to filter out energetic particles.
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Affiliation(s)
- Pradeep Bhadrachalam
- 1] Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019, USA [2] Nanotechnology Research Center, University of Texas at Arlington, Arlington, Texas 76019, USA
| | - Ramkumar Subramanian
- 1] Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019, USA [2] Nanotechnology Research Center, University of Texas at Arlington, Arlington, Texas 76019, USA
| | - Vishva Ray
- 1] Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019, USA [2] Nanotechnology Research Center, University of Texas at Arlington, Arlington, Texas 76019, USA
| | - Liang-Chieh Ma
- 1] Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019, USA [2] Nanotechnology Research Center, University of Texas at Arlington, Arlington, Texas 76019, USA
| | - Weichao Wang
- Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, USA
| | - Jiyoung Kim
- Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, USA
| | - Kyeongjae Cho
- Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, USA
| | - Seong Jin Koh
- 1] Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019, USA [2] Nanotechnology Research Center, University of Texas at Arlington, Arlington, Texas 76019, USA
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6
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Pal S, Ghosh M. Influence of damped propagation of dopant on the static and frequency-dependent third nonlinear polarizability of quantum dot. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.06.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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7
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Pal S, Ghosh M. Excitation kinetics of quantum dot induced by damped propagation of dopant: Role of confinement potential and magnetic field. Chem Phys 2013. [DOI: 10.1016/j.chemphys.2013.06.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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8
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Sippel P, Albrecht W, Mitoraj D, Eichberger R, Hannappel T, Vanmaekelbergh D. Two-photon photoemission study of competing Auger and surface-mediated relaxation of hot electrons in CdSe quantum dot solids. NANO LETTERS 2013; 13:1655-1661. [PMID: 23506122 DOI: 10.1021/nl400113t] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Solids composed of colloidal quantum dots hold promise for third generation highly efficient thin-film photovoltaic cells. The presence of well-separated conduction electron states opens the possibility for an energy-selective collection of hot and equilibrated carriers, pushing the efficiency above the one-band gap limit. However, in order to reach this goal the decay of hot carriers within a band must be better understood and prevented, eventually. Here, we present a two-photon photoemission study of the 1Pe→1Se intraband relaxation dynamics in a CdSe quantum dot solid that mimics the active layer in a photovoltaic cell. We observe fast hot electron relaxation from the 1Pe to the 1Se state on a femtosecond-scale by Auger-type energy donation to the hole. However, if the oleic acid capping is exchanged for hexanedithiol capping, fast deep hole trapping competes efficiently with this relaxation pathway, blocking the Auger-type electron-hole energy exchange. A slower decay becomes then visible; we provide evidence that this is a multistep process involving the surface.
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Affiliation(s)
- Philipp Sippel
- Helmholtz-Zentrum Berlin für Materialien und Energie, E-IF: Solar Fuels, Berlin, Germany
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Shi H, Yan R, Bertolazzi S, Brivio J, Gao B, Kis A, Jena D, Xing HG, Huang L. Exciton dynamics in suspended monolayer and few-layer MoS₂ 2D crystals. ACS NANO 2013; 7:1072-80. [PMID: 23273148 DOI: 10.1021/nn303973r] [Citation(s) in RCA: 315] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Femtosecond transient absorption spectroscopy and microscopy were employed to study exciton dynamics in suspended and Si₃N₄ substrate-supported monolayer and few-layer MoS₂ 2D crystals. Exciton dynamics for the monolayer and few-layer structures were found to be remarkably different from those of thick crystals when probed at energies near that of the lowest energy direct exciton (A exciton). The intraband relaxation rate was enhanced by more than 40 fold in the monolayer in comparison to that observed in the thick crystals, which we attributed to defect assisted scattering. Faster electron-hole recombination was found in monolayer and few-layer structures due to quantum confinement effects that lead to an indirect-direct band gap crossover. Nonradiative rather than radiative relaxation pathways dominate the dynamics in the monolayer and few-layer MoS₂. Fast trapping of excitons by surface trap states was observed in monolayer and few-layer structures, pointing to the importance of controlling surface properties in atomically thin crystals such as MoS₂ along with controlling their dimensions.
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Affiliation(s)
- Hongyan Shi
- Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA
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10
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Pazhanivel T, Devarajan VP, Bharathi G, Senthil K, Ganapathy V, Yong K, Nataraj D. Systematic investigation of the structure and photophysical properties of CdSe, CdSe/ZnS QDs and their hybrid with β-carotene. RSC Adv 2013. [DOI: 10.1039/c3ra41482e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Rukhlenko ID, Leonov MY, Turkov VK, Litvin AP, Baimuratov AS, Baranov AV, Fedorov AV. Kinetics of pulse-induced photoluminescence from a semiconductor quantum dot. OPTICS EXPRESS 2012; 20:27612-27635. [PMID: 23262711 DOI: 10.1364/oe.20.027612] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Optical methods, which allow the determination of the dominant channels of energy and phase relaxation, are the most universal techniques for the investigation of semiconductor quantum dots. In this paper, we employ the kinetic Pauli equation to develop the first generalized model of the pulse-induced photoluminescence from the lowest-energy eigenstates of a semiconductor quantum dot. Without specifying the shape of the excitation pulse and by assuming that the energy and phase relaxation in the quantum dot may be characterized by a set of phenomenological rates, we derive an expression for the observable photoluminescence cross section, valid for an arbitrary number of the quantum dot's states decaying with the emission of secondary photons. Our treatment allows for thermal transitions occurring with both decrease and increase in energy between all the relevant eigenstates at room or higher temperature. We show that in the general case of N states coupled to each other through a bath, the photoluminescence kinetics from any of them is determined by the sum of N exponential functions, whose exponents are proportional to the respective decay rates. We illustrate the application of the developed model by considering the processes of resonant luminescence and thermalized luminescence from the quantum dot with two radiating eigenstates, and by assuming that the secondary emission is excited with either a Gaussian or exponential pulse. Analytic expressions describing the signals of secondary emission are analyzed, in order to elucidate experimental situations in which the relaxation constants may be reliably extracted from the photoluminescence spectra.
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Affiliation(s)
- Ivan D Rukhlenko
- Advanced Computing and Simulation Laboratory (AχL), Department of Electrical and Computer Systems Engineering, Monash University, Clayton, VIC 3800, Australia.
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Mueller ML, Yan X, Dragnea B, Li LS. Slow hot-carrier relaxation in colloidal graphene quantum dots. NANO LETTERS 2011; 11:56-60. [PMID: 21126052 DOI: 10.1021/nl102712x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Reducing hot-carrier relaxation rates is of great significance in overcoming energy loss that fundamentally limits the efficiency of solar energy utilization. Semiconductor quantum dots are expected to have much slower carrier cooling because the spacing between their discrete electronic levels is much larger than phonon energy. However, the slower carrier cooling is difficult to observe due to the existence of many competing relaxation pathways. Here we show that carrier cooling in colloidal graphene quantum dots can be 2 orders of magnitude slower than in bulk materials, which could enable harvesting of hot charge carriers to improve the efficiency of solar energy conversion.
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Affiliation(s)
- Mallory L Mueller
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
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13
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Kwak DW, Park CJ, Lee YH, Kim WS, Cho HY. Extended defect states of Ge/Si quantum dots using optical isothermal capacitance transient spectroscopy. NANOTECHNOLOGY 2009; 20:055201. [PMID: 19417338 DOI: 10.1088/0957-4484/20/5/055201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We investigated the hole emission processes of optically induced charges on the defect states and confined states of self-assembled Ge quantum dots (QDs) embedded in a p-i-n Si diode. Optical deep level transient spectroscopy (ODLTS) and optical isothermal capacitance transient spectroscopy (OICTS) were used to study the defect states in ten stacked Ge quantum dots. Using ODLTS and OICTS for QD-embedded samples, the peaks related to the defect states of Ge QDs could be classified distinctly; it was about 20-50 times higher in intensity than that for the bulk defect states. The charges emitted from the QD defect state were observed near 93 K, and the activation energy was calculated to be E(V)+177 meV. The defect state followed the logarithmic capture kinetics and the Arrhenius-determined apparent activation energy decreased in the band gap as the optical injection width increased. We suggest that Ge QD defect states in Si could exist as extended states.
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Affiliation(s)
- D W Kwak
- Department of Physics and QSRC, Dongguk University, Korea
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15
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Pandey A, Guyot-Sionnest P. Multicarrier recombination in colloidal quantum dots. J Chem Phys 2007; 127:111104. [PMID: 17887819 DOI: 10.1063/1.2786068] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The rates of multicarrier recombination are measured in colloidal quantum dots with and without hole surface trapping and with hole extraction in type II core/shell systems. We report that hole trapping or the physical separation of electronic and hole wavefunctions into different semiconductor domains of a type II system have an insignificant effect on the multicarrier recombination dynamics. These observations are inconsistent with the accepted Auger transition mechanism.
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Affiliation(s)
- Anshu Pandey
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
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16
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Guyot-Sionnest P, Wehrenberg B, Yu D. Intraband relaxation in CdSe nanocrystals and the strong influence of the surface ligands. J Chem Phys 2005; 123:074709. [PMID: 16229612 DOI: 10.1063/1.2004818] [Citation(s) in RCA: 163] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The intraband relaxation between the 1Pe and 1Se state of CdSe colloidal quantum dots is studied by pump-probe time-resolved spectroscopy. Infrared pump-probe measurements with approximately 6-ps pulses show identical relaxation whether the electron has been placed in the 1Se state by above band-gap photoexcitation or by electrochemical charging. This indicates that the intraband relaxation of the electrons is not affected by the photogenerated holes which have been trapped. However, the surface ligands are found to strongly affect the rate of relaxation in colloid solutions. Faster relaxation (<8 ps) is obtained with phosphonic acid and oleic acid ligands. Alkylamines lead to longer relaxation times of approximately 10 ps and the slowest relaxation is observed for dodecanethiol ligands with relaxation times approximately 30 ps. It is concluded that, in the absence of holes or when the holes are trapped, the intraband relaxation is dominated by the surface and faster relaxation correlates with larger interfacial polarity. Energy transfer to the ligand vibrations may be sufficiently effective to account for the intraband relaxation rate.
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Ishigami M, Choi HJ, Aloni S, Louie SG, Cohen ML, Zettl A. Identifying defects in nanoscale materials. PHYSICAL REVIEW LETTERS 2004; 93:196803. [PMID: 15600863 DOI: 10.1103/physrevlett.93.196803] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2004] [Indexed: 05/24/2023]
Abstract
We have developed a novel iterative experimental-theoretical technique which can identify the atomic structure of defects in many-atom nanoscale materials from scanning tunneling microscopy and spectroscopy data. A given model for a defect structure is iteratively improved until calculated microscopy and spectroscopy data based on the model converge on the experimental results. We use the technique to identify a defect responsible for the electronic properties of a carbon nanotube intramolecular junction. Our technique can be extended for analysis of defect structures in nanoscale materials in general.
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Affiliation(s)
- Masa Ishigami
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
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18
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Blackburn JL, Ellingson RJ, Mićić OI, Nozik AJ. Electron Relaxation in Colloidal InP Quantum Dots with Photogenerated Excitons or Chemically Injected Electrons. J Phys Chem B 2002. [DOI: 10.1021/jp026746w] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jeff L. Blackburn
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, and Center for Basic Science, National Renewable Energy Laboratory, Golden, Colorado, 80401
| | - Randy J. Ellingson
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, and Center for Basic Science, National Renewable Energy Laboratory, Golden, Colorado, 80401
| | - Olga I. Mićić
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, and Center for Basic Science, National Renewable Energy Laboratory, Golden, Colorado, 80401
| | - Arthur J. Nozik
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, and Center for Basic Science, National Renewable Energy Laboratory, Golden, Colorado, 80401
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