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Arthur J. NOZIK Office Phone: 303 384 6603(NREL), 303 735 5703 (CU)
E-mail: anozik@nrel.gov
FAX: 303 384 6655
Lab: National Renewable Energy Laboratory
Lab Phone: 303 384 6603
Group Website: Nozik Group Website
Ph.D.: Yale University, 1967
Electron Transfer Dynamics Across Semiconductor-Molecule Interfaces and Size Quantization Effects in Semiconductors
Professor Nozik and his research group at the National Renewable Energy Laboratory (NREL) in Golden are engaged in two areas of research that deal with phenomena at semiconductor-molecule interfaces: (1) the dynamics of electron relaxation and transfer across these interfaces and (2) size quantization effects in ultra small (2 - 25 nm) semiconductor nanocrystals and structures (called quantum dots, quantum rods, and quantum wells).
Electron Relaxation Dynamics
Photoelectrochemical energy conversion of light to electricity or fuels (e.g., hydrogen, alcohols, or hydrocarbons) and heterogeneous photocatalysis depend upon the efficient spatial separation and subsequent interfacial charge transfer of electrons and positively charged holes (the two charges carriers) that are created upon the absorption of photons in the semiconductor or by the molecules at semiconductor-molecule interfaces. The separated electrons and holes can produce electrical power or drive electrochemical oxidation-reduction reactions with redox molecules at the semiconductor surfaces.
A critically important fundamental issue is the dynamics of relaxation of the photogenerated charge carriers. The relaxation processes include carrier or molecule cooling, radiative and non-radiative recombination, and electron and hole transfer across the semiconductor-molecule interface. Systems of interest include electron transfer from photoexcited dye molecules adsorbed on the semiconductor surface, as well as charge transfer from illuminated semiconductors to molecules at the interface.
These dynamics are studied theoretically and experimentally. The experimental studies utilize ultrafast time-resolved transient laser spectroscopy in the fs to ns time regime. This includes fs visible to mid-IR transient absorption spectroscopy, fs luminescence up-conversion spectroscopy,fs terahertz spectroscopy, and time-correlated (ps to ns) single photon counting measurements. Steady-state electrochemical impedance spectroscopy, photocurrent spectroscopy, photomodulation spectroscopy, and quartz crystal micro/nanobalance measurements are also used in these studies.
Semiconductor Quantum Dots/Nanocrystals and Nanostructures
When electrons and holes in semiconductors are confined to ultra-small regions of space (typically 1-25 nm), the semiconductor structure enters the regime of size quantization, wherein the electronic energy levels of the system become discrete rather than quasi-continuous, and the optical and electronic properties of the semiconductor become strongly size-dependent. Such structures are called quantum dots or nanocrystals, quantum rods, or quatnum wells depending upon their shape and dimensionality of the quantum confinement. We produce and study these quantization effects in colloidal semiconductor nanocrystals produced via chemical synthesis, as well as in quantized semiconductor structures produced via epitaxial growth in a Metallorganic Organic Chemical Vapor Deposition (MOCVD) reactor; Group IV, II-VI, IV-VI, and III-V semiconductors are typically the materials we study. Quantum dots and nanostructures are of great scientific interest and also have many important potential applications in quantum dot lasers, as photocatalysts, and in solar energy conversion. They show remarkable properties such as absorption and emission spectra that can shift by several eV as a function of quantum dot size, photoluminescence blinking, long-range energy transfer, enhanced non-linear optical effects, enhanced photoredox properties, and enhanced utilization of hot electrons via multiple exciton generation (MEG) or hot electron transport, interfacial transfer, and conversion.
CV of Arthur J. Nozik
Selected Publications on Quantum Dots
Bertram, D., M.C. Hanna and A.J. Nozik, “Two Color Blinking of Single Strain-Induced GaAs Quantum Dots,” Appl. Phys. Lett. 74, 2666–2668 (1999).
Mićić, O.I., S.P. Ahrenkiel, D. Bertram and A.J. Nozik, “Synthesis, Structure, and Optical Properties of Colloidal GaN Quantum Dots,” Appl. Phys. Lett. 75, 478–480 (1999).
Poles, E., D.C. Selmarten, O.I. Mićić and A.J. Nozik, “Anti-Stokes Photoluminescence in Colloidal Semiconductor Quantum Dots,” Appl. Phys. Lett. 75, 971–973 (1999).
Smith, B.B. and A.J. Nozik, “A Wave Packet Model for Electron Transfer and Its Implications for the Semiconductor-Liquid Interface,” J. Phys. Chem. B 103, 9915–9932 (1999).
Menoni, C.S., L. Miao, D. Patel, O.I. Mićić and A.J. Nozik, “Three-Dimensional Confinement in the Conduction Band Structure of InP,” Phys. Rev. Lett. 84, 4168–4171 (2000).
Mićić, O.I., B.B. Smith and A.J. Nozik, “Core-Shell Quantum Dots of Lattice-Matched ZnCdSe2 Shells on InP Cores: Experiment and Theory,” J. Phys. Chem. B 104, 12149–12156 (2000).
Smith, B.B. and A.J. Nozik, “Theoretical Studies of Electronic State Localization and Wormholes in Silicon Quantum Dot Arrays,” Nano Lett.1, 36–41 (2001).
Nozik, A.J.,“Spectroscopy and Hot Electron Relaxation Dynamics in Semiconductor Quantum Wells and Quantum Dots,” Ann. Rev. Phys. Chem. 52,193–231 (2001).
Mićić, O.I., S.P. Ahrenkiel and A.J. Nozik, “Synthesis of Extremely Small InP Quantum Dots and Electronic Coupling in Their Disordered Solid Films,” Appl. Phys. Lett. 78, 4022–4024 (2001).
Mićić, O.I., A.J. Nozik, E. Lifshitz, T. Rajh, O.G. Poluektov and M.C. Thurnauer, “Electron and Hole Adducts Formed in Illuminated InP Colloidal Quantum Dots Studied by Electron Paramagnetic Resonance,” J. Phys. Chem. 106, 4390–4395 (2002).
Langof, L., E. Ehrenfreund, E. Lifshitz, O.I. Mićić and A.J. Nozik, “Continuous-Wave and Time-Resolved Optically Detected Magnetic Resonance Studies of Non-Etched/Etched InP Nanocrystals,” J. Phys. Chem. B 106, 1606–1612 (2002).
Ellingson, R.J., J.L. Blackburn, P. Yu, G. Rumbles, O.I. Mićić and A.J. Nozik, “Excitation Energy Dependent Efficiency of Charge Carrier Relaxation and Photoluminescence in Colloidal InP Quantum Dots,“ J. Phys. Chem. B 106, 7758–7765 (2002).
Nozik, A.J., “Quantum Dot Solar Cells,” Physica E 14, 115–120 (2002).
Ellingson, R.J., J.L. Blackburn, J. Nedeljković, G. Rumbles, M. Jones, H. Fu and A.J. Nozik, “Experimental and Theoretical Investigation of Electronic Structure in Colloidal Indium Phosphide Quantum Dots,” Phys. Status Solidi C 0, 1229–1232 (2003).
Seong, M.J., O.I. Mićić, A.J. Nozik, A. Mascarenhas and H.M. Cheong, “Size-Dependent Raman Study of InP Quantum Dots,” Appl. Phys. Lett. 82, 185–187 (2003).
Blackburn, J.L., R.J. Ellingson, O.I. Mićić and A.J. Nozik, “Electron Relaxation in Colloidal InP Quantum Dots with Photogenerated Excitons or Chemically Injected Electrons,“ J. Phys. Chem. B 107, 102–109 (2003).
Ellingson, R.J., J.L. Blackburn, J. Nedeljković, G. Rumbles, M. Jones, H. Fu and A.J. Nozik, “Theoretical and Experimental Investigation of Electronic Structure and Relaxation in Colloidal Nanocrystalline Indium Phosphide Quantum Dots,” Phys. Rev. B. 67, 075308 (2003)
Ahrenkiel, S.P., O.I. Mićić, A. Miedaner, C.J. Curtis, J.M. Nedeljković and A.J. Nozik, “Synthesis and Characterization of Colloidal InP Quantum Rods,” Nano Lett. 3, 833–837 (2003).
Beard, M.C., G.M. Turner, J.E. Murphy, O.I. Mićić, M.C. Hanna, A.J. Nozik and C.A. Schmuttenmaer, “Electronic Coupling in InP Nanoparticle Arrays,” Nano Lett. 3, 1695–1699 (2003).
Blackburn, J.L., D.C. Selmarten and A.J. Nozik, “Electron Transfer Dynamics in Quantum Dot/Titanium Dioxide Composites Formed by in Situ Chemical Bath Deposition,” J. Phys. Chem. B 107, 14154–14157 (2003).
Hanna, M.C., O.I. Mićić, M.J. Seong, S.P. Ahrenkiel, J.M. Nedeljković and A.J. Nozik, “GaInP2 Overgrowth and Passivation of Colloidal InP Nanocrystals Using Metalorganic Chemical Vapor Deposition,” Appl. Phys. Letts. 84, 780–782 (2004).
Nedeljković, J.M., O.I. Mićić, S.P. Ahrenkiel, A. Miedaner and A.J. Nozik, “Growth of InP Nanostructures via Reaction of Indium Droplets with Phosphide Ions: Synthesis of InP Quantum Rods and InP-TiO2 Composites,” J. Am. Chem. Soc. 126, 2632–2639 (2004).
Yu, P., J.M. Nedeljković, P.A. Ahrenkiel, R.J. Ellingson and A.J. Nozik, “Size Dependent Femtosecond Electron Cooling Dynamics in CdSe Quantum Rods,” Nano Lett. 4, 1089–1092 (2004).
Langof, L., L. Fradkin, E. Ehrenfreund, E. Lifshitz, O.I. Mićić and A.J. Nozik, “Colloidal InP/ZnS Core-Shell Nanocrystals Studied by Linearly and Circularly Polarized Photoluminescence,” Chem. Phys. 297, 93–98 (2004).
Dimitrijević, N.M., T. Tajh, S.P. Ahrenkiel, J.M. Nedeljković, O.I. Mićić and A.J. Nozik, “Charge Separation in Heterostructures of InP Nanocrystals with Metal Particles,” J. Phys. Chem. B 109, 18243–18249 (2005).
Blackburn, J.L., D.C. Selmarten, R.J. Ellingson, M. Jones, O.I. Mićić and A. J. Nozik, “Electron and Hole Transfer from Indium Phosphide Quantum Dots,” J. Phys. Chem. B 109, 2625–2631 (2005).
Yu, P., M.C. Beard, R.J. Ellingson, S. Ferrere, C. Curtis, J. Drexler, F. Luiszer and A. J. Nozik, “Absorption Cross Section and Related Optical Properties of Colloidal InAs Quantum Dots,” J. Phys. Chem. B 109, 7084–7087 (2005).
Nozik, A. J., “Exciton Multiplication and Relaxation Dynamics in Quantum Dots: Applications to Ultrahigh-Efficiency Solar Photon Conversion,” Inorg. Chem. (Forum) 44, 6893–6899 (2005).
Ellingson, R.J., M.C. Beard, J. Johnson, P. Yu, O.I. Mićić, A.J. Nozik, A.J. Shaebev and Al.L. Efros,“ Highly Efficient Multiple Exciton Generation in Colloidal PbSe and PbS Quantum Dots,” Nano Lett. 5, 865–871 (2005).
Murphy, J.E., M.C. Beard, A.G. Norman, S.P. Ahrenkiel, J.C. Johnson, P. Yu, O.I. Mićić, R.J. Ellingson and A.J. Nozik, “PbSe Colloidal Nanocrystals: Synthesis, Characterization, and Multiple Exciton Generation,” J. Am. Chem. Soc. 128, 3241–3247 (2006).
Hanna M.C. and A.J. Nozik, “Solar Conversion Efficiency of Photovoltaic and Photoelectrolysis Cells with Carrier Multiplication Absorbers,” J. Appl. Phys. 100, 074510, 8 pages (2006).
Paci, I., J.C. Johnson, X. Chen, G. Rana, D. Popovic, D.E. David, A.J. Nozik, M.A. Ratner and J. Michl,“ Singlet Fission for Dye Sensitized Solar Cells: Can a Suitable Sensitizer be Found,” J. Amer. Chem. Soc. 128, 16546–16553 (2006).
Yu, P., K. Zhu, A.G. Norman, S. Ferrere, A.J. Frank and A.J. Nozik, “Nanocrystalline TiO2 Solar Cells Sensitized with InAs Quantum Dots,” J. Phys. Chem. B 110, 25451–25454 (2006).
Murphy, J.E., M.C. Beard and A.J. Nozik, “Time-Resolved Photoconductivity of PbSe Nanocrystal Arrays,” J. Phys. Chem. B 110, 25455–25461 (2006).
Shabaev, Al.L. Efros and A.J. Nozik, “Multi-Exciton Generation by a Single Photon in Nanocrystals,” NanoLett. 6, 2856–2863 (2006).
Ellingson, R., M. Beard, J. Johnson, J. Murphy, K. Knutsen, K. Gerth, J. Luther, M. Hanna, O. Mićić, A. Shabaev, A.L. Efros and A.J. Nozik, “Nanocrystals Generating >1 Electron per Photon May Lead to Increased Solar Cell Efficiency,” Article No. 10.1117/2.1200606.0229, SPIE Newsroom, 4 pages (2006).
Luque, A., A. Martí and A.J. Nozik, “Solar Cells Based on Quantum Dots: Multiple Exciton Generation and Intermediate Bands,” MRS Bull. 32, Special Issue on Photovoltaics, 236–241 (2007).
Luther, J.M., M.C. Beard, Q. Song,, M. Law, R.J. Ellingson, and A.J. Nozik, “Multiple Exciton Generation in Films of Electronically Coupled PbSe Quantum Dots,” Nano Lett. 7, 1779–1784 (2007).
Beard, M.C., K.K. Knutsen, P. Yu, J. Luther, Q. Song, R.J. Ellingson, and A.J. Nozik, “Multiple Exciton Generation in Colloidal Silicon Nanocrystals,” Nano Lett. 7, 2506–2512 (2007).
Johnson, J.C., Gerth, K.A., Song, Q., Murphy, J.E., Nozik, A.J., “Ultrafast Exciton Fine Structure Relaxation Dynamics in Lead Chalcogenide Nanocrystals” NanoLetters 8 1374-1381 (2008).
Luther, J.M., Law, M., Song, Q., Perkins, C.L., Beard, M.C., Nozik, A.J. “Structural, Optical, and Electrical Properties of Self-Assembled Films of PbSe Nanocrystals Treated with 1,2-ethanedithiol, ACS Nano 2, 271 (2008)
Nozik, A.J., “Multiple Exciton Generation in Semiconductor Quantum Dots”, Chem. Phys. Letters, Frontiers in Chemistry, 457, 3 – 11 (2008)
Law, M., . Luther, J.M. Song, Q., Perkins, C.L.,Nozik, A.J. “The Structural, Optical and Electrical Properties of PbSe Nanocrystal Solids Treated Thermally and with Simple Amines” JACS, 130, 5974-5985 (2008).
Luther,J.M., Law, M., Beard, M.C., Song, Q., Reese, M.O., Ellingson, R.J., Nozik, A.J., “Schottky Solar Cells Based on Colloidal Nanocrystal Films”, NanoLetters 8, 3488 (2008)
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