We are interested in photophysics in nano, molecular, and hybrid semiconductors and interfaces. A main focus is on the dynamics of quasiparticles, such as excitons, polarons, and polaritons, that are important to a range of optoelectronic processes. We employ state-of-the-art experimental techniques, including, among others, time-resolved photoemission spectroscopy, femtosecond nonlinear optical spectroscopies, transient absorption and time-resolved fluorescence spectroscopies and microscopies, 2D electronic spectroscopies, and scanning probe spectroscopies. As examples, recent discoveries in our lab revealed how dynamic screening and large polaron formation can make lead halide perovskite defect tolerant, how an exciton can split into two in organic semiconductors via the singlet fission process, and how an electron-hole pair can escape the Coulomb potential at a van der Waals interface.
Nicholas R. Monahan, Dezheng Sun, H. Tamura, Kristopher W. Williams, Bolei Xu, Yu Zhong, Bharat Kumar, Colin Nuckolls, Avetik R. Harutyunyan, Gugang Chen, Hai-Lung Dai, D. Beljonne, Yi Rao, X.-Y. Zhu, “Dynamics of the triplet pair state reveals the likely co-existence of coherent and incoherent singlet fission in crystalline hexacene,” Nature Chem. 2017, 9, 341-346.
Kiyoshi Miyata, Daniele Meggiolaro, M. Tuan Trinh, Prakriti P. Joshi, Edoardo Mosconi, Skyler Jones, Filippo De Angelis, X.-Y. Zhu, “Large polarons in lead halide perovskites,” Science Adv. 2017, 3, e1701217.
M. Tuan Trinh, Andrew Pinkard, Andrew B. Pun, Samuel N. Sanders, Elango Kumarasamy, Matthew Y. Sfeir, Luis M. Campos, Xavier Roy, X.-Y. Zhu, “Distinct properties of the triplet pair state from singlet fission,” Science Adv. 2017, 3, e1700241.
Gregory D. Scholes, Graham R. Fleming, Lin X. Chen, Alán Aspuru-Guzik, Andreas Buchleitner, David F. Coker, Gregory S. Engel, Rienk van Grondelle, Akihito Ishizaki, David M. Jonas, Jeff S. Lundeen, James K. McCusker, Shaul Mukamel, Jennifer P. Ogilvie, Alexandra Olaya-Castro, Mark A. Ratner, Frank C. Spano, K. Birgitta Whaley, X.-Y. Zhu, “Utilizing Coherence to Enhance Function in Chemical and Biophysical Systems” Nature, 2017, 543, 647-656.
Haiming Zhu, Kiyoshi Miyata, Yongping Fu, Jue Wang, Prakriti P. Joshi, Daniel Niesner, Kristopher J. Williams, Song Jin, X.-Y. Zhu, “Screening in crystalline liquids protects energetic carriers in hybrid perovskites,” Science, 2016, 353, 1409-1413.
Haiming Zhu, 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 high quality factors,” Nature Mater. 2015, 14, 636-642.
A. Jailaubekov, A. P. Willard, J. Tritsch, W.-L. Chan, N. Sai, R. I. Gearba, L. G. Kaake, K. J. Williams, 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. 2013, 12, 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. 2012, 4, 840-845.
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 2011, 334, 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 2010, 328, 1543-1547.