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Perovskite Photovoltaics. Visualizing Halide Ion Mobility in Mixed Halide Perovskites.

Department of Materials Science & Engineering
Tuesday February 18, 2020
9:45 – 10:45AM ~ Ferris Hall 502
                 Please join us for refreshments at 9:40

"Perovskite Photovoltaics. Visualizing Halide Ion Mobility in Mixed Halide Perovskites."

Speaker: Dr. Prashant V. Kamat, Rev. John A. Zahm, C.S.C.Professor of Science
Radiation Laboratory & Department of Chemistry & Biochemistry
Concurrent Professor: Department of Chemical & Biomolecular Engineering
University of Notre Dame-Notre Dame, IN

The intrinsic ionic defects, specifically halide ion vacancies, often dictate the mobility of halide species within the perovskite film during the operation of solar cells. Of particular interest is the halide ion mobility in metal halide perovskites, which plays an important role in determining the performance of perovskite solar cells. Photoinduced phase segregation seen in mixed halide perovskite films under steady state irradiation offers a convenient way to visualize halide ion segregation. Interestingly, upon storage in dark, the process is reversed and the original mixed halide composition gets restored. Whereas entropy of mixing explains the thermally activated mixing of halide ions to yield mixed halide perovskite, the opposite trend observed during photoirradiation remains an intriguing phenomenon. The threshold energy of incident light to observe halide segregation increases with increasing temperature. The diffusion of these halide species, which is tracked through changes in the absorption spectra at different temperatures, offers a direct measurement of thermally activated halide diffusion in perovskite films. The increase in the rate constant of halide diffusion with increasing temperature (from 5×10-5 s–1 at 23 °C to 2.2×10-3 s–1 at 140 °C) follows an Arrhenius relationship with activation energy of 51 kJ/mole.  The thermally activated halide exchange shows the challenges of employing layers of different metal halide perovskites in stable tandem solar cells.
P.V.K. acknowledges the support of the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy, through award DE-FC02-04ER15533.
1.    Yoon, S. J.; Draguta, S.; Manser, J. S.; Sharia, O.; Schneider, W. F.; Kuno, M.; Kamat, P. V. Tracking Iodide and Bromide Ion Segregation in Mixed Halide Lead Perovskites during Photoirradiation, ACS Energy Letters 2016, 1, 290-296.
2.    Yoon, S. J.; Kuno, M.; Kamat, P. V. Shift Happens. How Halide Ion Defects Influence Photoinduced Segregation in Mixed Halide Perovskites, ACS Energy Letters 2017, 2, 1507–1514.
3.    Draguta, S.; Sharia, O.; Yoon, S. J.; Brennan, M. C.; Morozov, Y. V.; Manser, J. M.; Kamat, P. V.; Schneider, W. F.; Kuno, M. Rationalizing the Light-Induced Phase Separation of Mixed Halide Organic-Inorganic Perovskites, Nature Communications 2018, 8, Article No. 200 (DOI: 10.1038/s41467-017-00284-2).
4.    Samu, G. F.; Janáky, C.; Kamat, P. V. A Victim of Halide Ion Segregation. How Light Soaking Affects Solar Cell Performance of Mixed Halide Lead Perovskites, ACS Energy Letters 2017, 2, 1860-1861.
5.    Elmelund, T.; Brian Seger, B.; Kuno, M. K.; Kamat, P. V. How Interplay between Photo and Thermal Activation Dictates Halide Ion Segregation in Mixed Halide Perovskites, ACS Energy Letters, 2020, 5, 56-63.

Prashant V. Kamat is a Rev. John A. Zahm, C.S.C., Professor of Science in the Department of Chemistry and Biochemistry and Radiation Laboratory at the University of Notre Dame. He is also a Concurrent Professor in the Department of Chemical and Biomolecular Engineering.  He earned his doctoral degree (1979) in Physical Chemistry from the Bombay University, and postdoctoral research at Boston University (1979-1981) and University of Texas at Austin (1981-1983). He joined Notre Dame in 1983. Professor Kamat has for more than three decades worked to build bridges between physical chemistry and material science to develop advanced nanomaterials that promise cleaner and more efficient light energy conversion. 

He has directed DOE funded solar photochemistry research for the past 35 years. In addition to large multidisciplinary interdepartmental and research center programs, he has actively worked with industry-sponsored research. He has served on many national panels on nanotechnology and energy conversion processes. He has published more than 450 scientific papers that have been well recognized by the scientific community (68000 citations, h-index 133 –Source Web of Science). Thomson-Reuters has featured him as one of the most cited researchers each year during 2014-2019.

He is currently serving as the Editor-in-Chief of ACS Energy Letters. He has also served as the deputy editor of the Journal of Physical Chemistry Letters. He is a member of the advisory board of several scientific journals (Chemical Reviews, Journal of Colloid & Interface Science, ACS Applied Nanomaterials, Research on Chemical Intermediates, and Applied Electrochemistry). He was awarded Honda-Fujishima Lectureship award by the Japanese Photochemical Society in 2006, CRSI medal by the Chemical Research Society of India in 2011 and Langmuir lectureship award in 2013. He is a Fellow of the Electrochemical Society (ECS), American Chemical Society (ACS) American Association for the Advancement of Science (AAAS) and Pravasi Fellow of the Indian National Science Academy.

Faculty Host: Dr. Bin Hu

Tuesday, February 18, 2020 at 9:45am to 10:45am

Ferris Hall, 502
1508 Middle Drive, Knoxville, TN 37996

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