In-situ Observation of Trapped Carriers in Organic Metal Halide Perovskite Films with Ultra-fast Temporal and Energy Resolutions (06/07/22)

Speaker and Affliation:

Prof. Apparao M. Rao
Clemson University, USA)


Prof. Apparao M. Rao Department of Physics and Astronomy, and Clemson Nanomaterials Institute Prof. Apparao is visiting as Dr Brahm Prakash Chair professorship at the Department of Materials Engineering. He is a physicist and a nanomaterials researcher. He currently serves as the Robert A. Bowen Professor of Physics in the Department of Physics and Astronomy, Clemson University, and the founding director of the Clemson Nanomaterials Institute. He has also served as the Associate Dean for Discovery in the College of Science, Clemson University. He is known for developing Raman spectroscopy as a versatile tool for characterizing carbon nanomaterials and developing liquid-injection-based synthesis methods for carbon nanotubes. His current research at Clemson University focuses on energy generation and storage technologies. In addition to supporting R&D at Clemson University through federal funding, Rao has successfully attracted funding and fostered strong industrial partnerships. Because of his sustained research in nanomaterials and for building competitiveness in the State of South Carolina, the Governor of South Carolina, the Honorable Nikki Haley, conferred on him in 2014 the State’s highest honour - the Governor’s award for excellence in scientific research. He is a TEDxGreenville Speaker and a Fellow of the American Physical Society, American Association for the Advancement of Science, Materials Research Society, and the National Academy of Inventors.


06th July, 2022 (Wednesday), 11:00 AM (India Standard Time)


Department of Materials Engineering, KPA auditorium


We in situ observe the ultrafast dynamics of trapped carriers in organic methyl ammonium lead halide perovskite thin films by ultrafast photocurrent spectroscopy with a sub-25 picosecond time resolution. Upon ultrafast laser excitation, trapped carriers follow a phonon-assisted tunneling mechanism and a hopping transport mechanism along ultra-shallow to shallow trap states ranging from 1.72-11.51 millielectronvolts and are demonstrated by time-dependent and independent activation energies. In addition to carrier mobility of ~ 4 cm2/V.s and lifetime of ~ 1 nanosecond, we validate the above transport mechanisms by highlighting trap state dynamics, including trapping rates, de-trapping rates, and trap properties such as trap density, trap levels, and capture-cross sections. This work [1] establishes a foundation for trap dynamics in high defect-tolerant perovskites with ultra-fast temporal and ultra-high energy resolution.

[1] Nature Communications, 12 (2021).