Prashant V. Kamat
Karnatak University, B.S. (1972)
Bombay University, India, M.S. (1974) Ph.D (1979)
Phone: (574) 631-5411
Email: Kamat.1@nd.edu
Office: 223B Radiation Research Building
Charge Transfer Processes and Energy Conversion
Scientific Interests
Light Harvesting Assemblies
Elucidation of excited state dynamics, energy and electron transfer, and surface chemistry of semiconductor quantum dots and metal halide perovskite nanocrystal based assemblies.
Photocatalysis
Interfacial charge transfer at semiconductor and metal interface, role of metal nonoparticles as co-catalysts in photocatalysis and design of hybrid assemblies for light energy conversion.
Electrochemistry at the Mesoscale
Evaluation of electrocatalytic and photocatalytic processes and modulation of charge transfer at the electrode/electrolyte interface through applied bias.
Recent Accomplishments
Halide Ion Migration in Metal Halide Perovskites
In the operation of a perovskite solar cell the electron transport layer (ETL) and hole transport layer (HTL) interact with metal halide perovskite films and drive away electrons and holes respectively. Transporting holes across the HTL interface with a rate similar to the electron transfer rate is crucial for achieving stable photovoltaic performance. The electron capture property of ETL indirectly affects halide ion mobility as evident from the TiO2-assisted halide ion segregation in mixed halide perovskite (MHP) films under pulsed laser excitation (387 nm, 500 Hz). This segregation is only observed when deposited on an ETL such as TiO2 but not on insulating ZrO2 substrate. Injection of electrons from excited MHP into the ETL (ket = 1011 s–1) followed by scavenging of electrons by O2 causes hole accumulation in the MHP film. Localization of holes on the iodide site in the MHP induces instability causing iodide from the lattice to move away toward grain boundaries. This hole accumulation effect on the mobility of iodine can be modulated through the application of electrochemical bias.
Perovskite Photocatalysis
The photocatalytic properties of cesium lead bromide (CsPbBr3) perovskite nanocrystals make them attractive for designing light harvesting assemblies. Often ignored, the surface chemistry can dictate the excited state interactions of these semiconductor nanocrystals with charge-shuttling redox molecules. Surface interactions with the ferrocenium/ferrocene redox couple have shown that surface-bound redox species can dictate the excited-state dynamics of CsPbBr3 nanocrystals. Similarly, the strong binding between CsPbBr3 nanocrystals and methyl viologen induces a long-lived charge-separated state following band gap excitation with important implications in photocatalytic processes. The unusually long-lived bleaching of the CsPbBr3 excitonic peak in this case arises from the creation of a dipole with the hole residing in CsPbBr3 and the electron in the surface-bound methyl viologen moiety.
Excited State Dynamics of 2D Perovskites
Two-dimensional (2D) lead halide perovskites with better chemical stability and tunable dimensionality offer new opportunities to design optoelectronic devices. 2D lead halide (bromide and iodide) perovskites of different dimensionality were prepared by varying the ratio of methylammonium:phenylethylammonium cation. With decreasing dimensionality (n = ∞ → 1). We observe a blue shift in transient absorption bleach in agreement with the trend observed with the shift in the excitonic peak. The lifetime of the charge carriers decreased with decreasing layer thickness. The dependence of charge carrier lifetime on the 2D layers as well as the halide ion composition shows the dominance of excitonic binding energy on the charge carrier recombination in 2D perovskites. The excited-state behavior of 2D perovskites show the need to modulate the layer dimensionality to obtain desired optoelectronic properties.
Selected Publications
Kamat, P.V., M. Kuno. "Halide Ion Migration in Perovskite Nanocrystals and Nanostructures." Acc. Chem. Res. 54 (2021) 520-531. link
DuBose, J.T., P.S. Mathew, J. Cho, M. Kuno, P.V. Kamat. "Photoinduced Iodine Expulsion in Mixed Halide Perovskites with Electrochemical Bias." J. Phys. Chem. Lett. 12 (2021) 2615-2621. link
Cho, J., J.T. DuBose, P.S. Mathew, P.V. Kamat. "Electrochemically Induced Iodine Migration in Mixed Halide Perovskites: Suppression through Chloride Insertion." Chem. Comm. 57 (2021) 235-238. link
DuBose, J.T., P.V. Kamat. "TiO2-Assisted Halide Ion Segregation in Mixed Halide Perovskite Films." J. Am. Chem. Soc. 42 (2020) 5362-5370. link
Brennan, M.C., A. Ruth, P.V. Kamat, M. Kuno. "Photoinduced Anion Segregation in Mixed Halide Perovskites." Trends in Chemistry (Cell Press) 2 (2020) 282-301. link
Cho, J-S, J.T. DuBose, P.V. Kamat. "Charge Carrier Recombination Dynamics of Two-Dimensional Lead Halide Perovskites." J. Phys. Chem. Lett. 11 (2020) 2570-2576. link