550 120th Street
1312 Northwest Corner
New York, NY 10027
Solar energy conversion, photophysics, ultrafast spectroscopy, & interfacial science
A main research thrust in my group is to discover new photophysical mechanisms and formulate new solar energy conversion strategies with efficiency potentially approaching or exceeding the “Shockley-Queisser” limit. One of the key questions we are focusing on is at the heart of future photovoltaic technology: How can one extract electrons and holes from photo-generated excitons in molecular or nanomaterials? To answer this question, we use model material systems and state-of-the-art laser spectroscopic techniques, including femtosecond time-resolved two-photon photoemission (2PPE) spectroscopy and time-resolved second harmonic generation (SHG). As examples, recent discoveries in our lab showed how an electron and a hole is bound by the Coulomb potential across an organic semiconductor interface, how one can extract hot electrons from a photoexcited quantum dot, and how the absorption of one photon can give two electron-hole pairs via the singlet fission process. Our lab is part of the Energy Frontier Research Center on Redefining Photovoltaic Efficiency through Molecule Scale Control. In addition to solar energy conversion, we are interested in the general challenge of understanding many-body interactions in condensed matter. Another small thrust in the group is to understand fundamental physical principles underlying bio-interfacial interactions, such as protein-glycan interaction on the surface of cell membranes.
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A. Jailaubekov, A. P. Willard, J. Tritsch, W.-L. Chan, N. Sai, L. Kaake, R. I. Gearba, K. Leung, P. J. Rossky, X.-Y. Zhu, “Hot charge transfer excitons set the time limit for charge separation at donor/acceptor interfaces in organic photovoltaics,” Nature Mater. 12 (2013) 66-73.
W.-L. Chan, M. Ligges, X.-Y. Zhu, “The energy barrier in singlet fission can be overcome through coherent coupling and entropic gain,” Nature Chem. 4 (2012) 840-845.
W.-L. Chan, J. R. Tritsch, X.-Y. Zhu, “Harvesting singlet fission for solar energy conversion: one versus two electron transfer from the quantum mechanical superposition,” J. Am. Chem. Soc. 134 (2012) 18295–18302.
L. Shen, T. Adachi, D. A. Venden Bout, X.-Y. Zhu, “A mobile precursor determines amyloid-β peptide fibril formation at the liquid-solid interface,” J. Am. Chem. Soc. 134 (2012) 14172–14178.
C. A. Nelson, X.-Y. Zhu, “Reversible electronic traps in PbS quantum dot solids induced by an order-disorder phase transition in capping molecules,” J. Am. Chem. Soc. 134 (2012) 7792-7795.
L. Miaja-Avila, J. Tritsch, A. Wolcott, W.-L. Chan, C. A. Nelson, X.-Y. Zhu, “Direct mapping of hot electron relaxation and multiexciton generation dynamics in PbSe quantum dots,” Nano Lett. 12 (2012) 1588-1591.
W.-L. Chan, M. Ligges, A. Jailaubekov, L. Kaake, L. Miaja-Avila, X.-Y. Zhu, “Observing the multi-exciton state in singlet fission and ensuing ultrafast multi-electron transfer,” Science 334 (2011) 1541-1545.
W. A. Tisdale, K. J. Williams, B. A. Timp, D. J. Norris, E. S. Aydil, X.-Y. Zhu, “Hot electron transfer from semiconductor nanocrystals,” Science 328 (2010) 1543-1547.
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