PHYS Seminar: “Polaronic Excitons in Lead Halide Perovskites”, Tuğrul Senger, January 31 2024 (EN)

Prof. Dr. R. Tuğrul Senger
Department of Physics, İzmir Institute of Technology

“Polaronic Excitons in Lead Halide Perovskites”


Hybrid organic–inorganic lead halide perovskites are promising materials for photovoltaic and optoelectronic applications. In this talk, I will present temperature-dependent diffusion characteristics of photogenerated carriers in single-crystal microstructures of methylammonium lead iodide/bromide (MAPbI3 and MAPbBr3) as obtained by using scanning photocurrent microscopy. We observe an interesting abrupt enhancement in carrier diffusion lengths during the tetragonal to orthorhombic phase transitions of these crystals. Specifically, at 80 K, the carrier diffusion length reaches a significant value of 200±50 μm for MAPbI3. We attribute this phenomenon to the efficient formation and diffusion of free excitons within the low-temperature phase of these materials. Regarding the strong electron-phonon coupling in hybrid halide perovskites, we propose dominance of polaronic-excitons as a potential mechanism for the observed increase in carrier diffusion lengths at lower temperature.

Dr. Tuğrul Senger received his Ph.D. in year 2000 from Bilkent University. He was a postdoctoral research fellow at Emory University, Atlanta, USA during 2001-03. Dr. Senger joined Bilkent University in 2004 as an Assistant Professor. In 2009 he moved to İzmir Institute of Technology (IZTECH) as an Associate Professor. Currently, he is a full professor at IZTECH since 2011. He was a visiting professor at University of California – Davis in 2019-20 academic year as a Fulbright scholar. His research interests include computational materials science; quantum transport in nanostructures; electron-phonon interaction in low dimensional systems; and theory of polarons, bipolarons, and excitons. Dr. Senger received undergraduate scholarships from Bilkent University, TÜBİTAK and VAKSA, and graduate fellowship from Münir Birsel Foundation. He received 2006 “Young Investigator Award (GEBİP)” of Turkish Academy of Sciences (TÜBA), 2009 “Young Scientist Award” of FABED, and 2010 “Research Incentive Award” of ODTÜ Parlar Foundation. He is a member of The Science Academy, Turkey (Bilim Akademisi).

Date: January 31, 2024 Wednesday
Time: 15:30
Place: SA-240