Understanding Halide Ion Mobility in Lead Halide Perovskite Solar Cells
Prashant Kamat a
a Radiation Laboratory, Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, IN 46556
nanoGe Perovskite Conferences
Proceedings of nanoGe International Conference on Perovskite Solar Cells, Photonics and Optoelectronics (NIPHO19)
International Conference on Perovskite Thin Film Photovoltaics
Jerusalem, Israel, 2019 February 24th - 27th
Organizers: Lioz Etgar and Kai Zhu
Invited Speaker, Prashant Kamat, presentation 072
DOI: https://doi.org/10.29363/nanoge.nipho.2019.072
Publication date: 21st November 2018

Halide ions are known to be mobile both in dark as well as under bandgap excitation.  The halide ion mobility is often dictated by the defects and halide ion composition. The excited state characterization using emission and transient absorption spectroscopy has allowed us to probe the halide ion migration and segregation in methylammonium lead iodide/bromide (CH3NH3PbBrxI3-x (x=0 to 3)). In addition to composition dependent absorption and emission properties they also undergo phase segregation to create Iodine-rich and Bromide- rich regions when subjected to visible irradiation. This intriguing aspect of halide ion movement in these mixed halide films can be tracked from the changes in the photoluminescence and absorption spectra. The photovoltaic performance decreases with continuous illumination even without external load. Upon storing these perovskite solar cells in dark, the photovoltaic performance recover indicating remixing of the halide ions. This recovery in photovoltaic performance is in line with the absorption recovery of the mixed halide band. The results that show the dependence of the photocurrent and photovoltage recovery on the iodide treatment will be discussed.

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