Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

ON THE ORIGIN OF SPATIALLY DEPENDENT ELECTRONIC EXCITED-STATE DYNAMICS IN MIXED HYBRID PEROVSKITE THIN FILMS*
Ying-Zhong Ma^a, Benjamin Doughty^a, Mary Jane Simpson^a, Sanjib Das^b, and Kai Xiao^c
^aChemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
^bDepartment of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, Tennessee 37996
^cCenter for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
E-mail: may1@ornl.gov
Received 15 November 2018; accepted 2 January 2019

The fundamental photophysics underlying the remarkable performance of organic-inorganic hybrid perovskites in optoelectronic device applications has been increasingly studied using complementary spectroscopic techniques. However, the spatially heterogeneous polycrystalline morphology of the solution-processed thin films is often overlooked in conventional ensemble measurements and therefore the reported results are averaged over hundreds or even thousands of nano- and micro-crystalline grains. Here, we apply femtosecond transient absorption microscopy to spatially and temporally probe ultrafast electronic excited-state dynamics in chloride containing mixed lead halide perovskite (CH₃NH₃PbI_3–xCl_x) thin films. We found that the electronic excited-state relaxation kinetics are extremely sensitive to the spatial location probed, which was manifested by position-dependent transient absorption signal amplitude and decay behaviour, along with an obvious rise component at some positions. The analysis of transient absorption kinetics acquired at several distinct spatial positions enabled us to identify Auger recombination as the dominant mechanism underlying the initial portions of the spatially dependent dynamics with variable rate constants. The different rates observed suggest occurrence of distinct local electronic structures and variable contributions from impurities/defects and phonons in this nonlinear dynamical process.

Keywords: transient absorption microscopy, ultrafast electronic excited-state dynamics, Auger recombination, metal halide perovskites

*This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide licence to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (https://energy.gov/downloads/doe-public-access-plan).

DĖL ERDVIŠKAI PRIKLAUSOMŲ ELEKTRONINIŲ SUŽADINTŲ BŪSENŲ DINAMIKOS MIŠRIŲJŲ HIBRIDINIŲ PEROVSKITŲ PLONUOSIUOSE SLUOKSNIUOSE KILMĖS
Ying-Zhong Ma^a, Benjamin Doughty^a, Mary Jane Simpson^a, Sanjib Das^b, Kai Xiao^a

^aOuk Ridžo nacionalinė laboratorija, Ouk Ridžas, Tenesis
^bTenesio universitetas, Noksvilis, Tenesis

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