报告题目：Solvingthe Lead Halide Perovskite Puzzle
报告人：XiaoyangZhu教授
Department of Chemistry,Columbia University, New York, NY 10027
报告时间：2016年11月29日（星期二）上午10:00-11:00
报告地点：材化部907-1445报告厅
报告摘要：
The feverish research activityon lead halide perovskites has been fueled by their exceptional optoelectronicproperties, e.g., in solar cells and light-emitting devices. Hybrid lead halideperovskites exhibit carrier properties that resemble those of pristine nonpolarsemiconductors despite static and dynamic disorder, but how carriers areprotected from efficient scattering with charged defects and optical phonons isunknown. We have recently put forward the large polaronmodel to explain the carrier protection [1,2]. We find that nascent chargecarriers are screened by “solvation” or large-polaron formation on time scales≤ 250 fs, leading to protected carriers with dramatic suppression of electron-LO phonon scattering. This results in long-lived energetic electrons withexcess energy ~ 0.25 eV above the conduction band minimum and with lifetime onthe order of 100 ps, which is ≥103 time longer than those inconventional semiconductors. The exceptionally long-lived energetic carrierslead to hot fluorescence emission on the ~100-200 ps time scale. The protectionof energetic carriers is directly correlated with the liquid-like motion oforganic cations, as revealed by femtosecond Kerr-effect spectroscopy. Incontrast to that of energetic carriers, the protection of long-lived bandedgecarriers do not require the presence of organic cations and is an intrinsicproperty of the soft perovskite lattice [3]. Finally, we will discuss stronglight-matter interaction leading to efficient exciton-polariton formation andour most recent observation of coherent light emission without populationinversion; this is distinctively different than our earlier findings ofefficient lasing in these materials [4].
[1] X.-Y.Zhu, V. Podzorov, “Charge carriers in hybrid organic-inorganic leadhalide perovskites might be protected as large polarons,” J. Phys. Chem. Lett. 2015, 6, 4758-4761.
[2] Haiming Zhu, Kiyoshi Miyata, Yongping Fu, JueWang, Prakriti P. Joshi, Daniel Niesner,Kristopher K. Williams, Song Jin, X.-Y.Zhu, “Screening in crystalline liquids protects energetic carriers in hybridperovskites,” Science, 2016,353, 1409-1413.
[3] HaimingZhu, M. Tuan Trinh, YongpingFu, Jue Wang, Prakriti P. Joshi, Kiyoshi Miyata, Song Jin, X.-Y. Zhu, “Organic cations might not be essential forthe exceptional properties of bandedge carriers in lead halide perovskites,” Adv. Mater. 2016, 28, DOI:10.1002/adma.201603072.
[4] HaimingZhu, Yongping Fu, Fei Meng, Xiaoxi Wu,Zizhou Gong, Qi Ding, Martin V. Gustafsson, M. Tuan Trinh, Song Jin, X.-Y. Zhu,“Lead halide perovskite nanowire lasers with low lasing thresholds and highquality factors,” Nature Mater. 2015, 14, 636-642.
报告人XiaoyangZhu教授简历
Department of Chemistry, Columbia University,e-mail: xz2324@columbia.edu
ProfessionalPreparation
1.Fudan University, Shanghai Chemistry B.S 1984
2.University of Texas, Austin Chemistry Ph.D. 1989
3.University of Texas, Austin Chemistry Postdoc 1990-1992
4.Fritz-Haber-Institute, Berlin SurfaceScience Postdoc 1992-1993
Appointments
07/1993–06/1997 AssistantProfessor of Chemistry, Southern Illinois Univ., Carbondale.
07/1997-06/2002 Associate Professorof Chemistry, University of Minnesota.
07/2002-06/2008 Professor ofChemistry, University of Minnesota
07/2008-06/2009 Merck EndowedProfessor of Chemistry, University of Minnesota
10/2010-05/2012 Director, DOEEnergy Frontier Research Center at UT Austin
07/2009-12/2012 L. N. VauquelinRegents Professor of Chemistry, UT Austin
07/2009-12/2012 Director, Centerfor Materials Chemistry, UT Austin
01/2013-present Professor ofChemistry, Columbia University
Honors &Awards
Alexander-von-Humboldt Fellowship, HumboldtFoundation, 1992.
Camille and Henry Dreyfus New Faculty Award,Dreyfus Foundation, 1993.
Cottrell Scholar Award, Research Corporation, 1996.
Friedrich Wilhelm Bessel Award, HumboldtFoundation, 2006.
Fellow of the American Physical Society, 2011.
Other distinctions
Brian Bent Memorial Lecturer, Columbia University,02/15/2007.
Plenary Lecturer, 31st DOE Solar Photochem.Meeting, Annapolis, MD, 06/07/2009.
Welch Lecturer, Welch Conference, Houston, TX, 10/25/2010
Milton Kahn Lecturer, University of New Mexico,Albuquerque, NM, 04/22/2011
Plenary/public lecturer, I-CAMP Summer School,Boulder, CO, 08/10/2012
Plenary lecturer, Southeast Ultrafast Conference, Atlanta,GA, 01/11/2013
Plenary lecturer, ICSFI-14, Gyeongju, Korea,07/03/2013
R.B. Woodward Lecturer in the Chemical Sciences,Harvard University, 10/10/2013
ResearchInterests
Light-matter interaction, solar energy conversion,ultrafast spectroscopy. A main research thrust is to establish newphotophysical mechanisms that may be utilized to revolutionize solar energyconversion or light emission. As examples, recent discoveries in our lab showedhow an electron and a hole is bound by the Coulomb potential across an organicsemiconductor interface, how one can extract hot electrons from a photoexcitedquantum dot, how an exciton can split into two via the singlet fission process,and how charge carriers can recombine in semiconductor nanostructures for laseremission.
（报告联系人：李华老师、徐庆锋老师）