How Interplay between Photo and Thermal Activation Dictates Halide Ion Segregation in Mixed Halide Perovskites

Elmelund, Tor; Seger, Brian; Kuno, Masaru; Kamat, Prashant V.

doi:10.1021/acsenergylett.9b02265

Title: How Interplay between Photo and Thermal Activation Dictates Halide Ion Segregation in Mixed Halide Perovskites

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Abstract

The halide ion mobility in mixed halide perovskite demonstrates two opposite trends in response to photo and thermal activation. While halides prefer to remain as Br-rich and I-rich domains under steady-state light irradiation of MAPbBr_1.5I_1.5 films, they prefer to remain in their stable mixed composition when kept in the dark. The activation energies as determined from the temperature-dependent rate constants are E_a,forward = 28.9 kJ mol^–1 for photoinduced segregation and E_a,reverse = 53.5 kJ mol^–1 for remixing of halides in the dark, respectively. The energy input from photoexcitation assists overcoming the dark (thermally activated) mixing to induce Br-rich and I-rich domains. This segregated state is maintained as long as the mixed halide film is irradiated continuously with visible light. The excitation intensity threshold above which segregation occurs follows a linear temperature dependence, such that phase separation occurs above I_exc = 30 μW/cm² white light at 23 °C. The threshold at 90 °C becomes higher with a minimum intensity requirement of 100 μW/cm² to induce segregation. The thermodynamic rationale behind this unusual halide mobility under photo and thermal excitation discussed here can aid in understanding the stability issues of perovskite solar cells.

Authors:

Elmelund, Tor ^[1];

^[2];

^[3];

^[3]

Univ. of Notre Dame, IN (United States); Technical Univ. of Denmark, Lyngby (Denmark)
Technical Univ. of Denmark, Lyngby (Denmark)
Univ. of Notre Dame, IN (United States)

Publication Date:: 2019-11-20

Research Org.:: Univ. of Notre Dame, IN (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division; Villum Foundation; USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division

OSTI Identifier:: 1657796

Grant/Contract Number:: SC0014334; FC02-04ER15533; 9455

Resource Type:: Accepted Manuscript

Journal Name:: ACS Energy Letters

Additional Journal Information:: Journal Volume: 5; Journal Issue: 1; Journal ID: ISSN 2380-8195

Publisher:: American Chemical Society (ACS)

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; Inorganic compounds; Absorption; Perovskites; Halogens; Ions

Citation Formats


                    Elmelund, Tor, Seger, Brian, Kuno, Masaru, and Kamat, Prashant V. How Interplay between Photo and Thermal Activation Dictates Halide Ion Segregation in Mixed Halide Perovskites.  United States: N. p., 2019. 
Web.  doi:10.1021/acsenergylett.9b02265.

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                    Elmelund, Tor, Seger, Brian, Kuno, Masaru, & Kamat, Prashant V. How Interplay between Photo and Thermal Activation Dictates Halide Ion Segregation in Mixed Halide Perovskites.  United States.  https://doi.org/10.1021/acsenergylett.9b02265

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                    Elmelund, Tor, Seger, Brian, Kuno, Masaru, and Kamat, Prashant V. Wed .  
"How Interplay between Photo and Thermal Activation Dictates Halide Ion Segregation in Mixed Halide Perovskites".  United States.  https://doi.org/10.1021/acsenergylett.9b02265.  https://www.osti.gov/servlets/purl/1657796.

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@article{osti_1657796,

  title        = {How Interplay between Photo and Thermal Activation Dictates Halide Ion Segregation in Mixed Halide Perovskites},

  author       = {Elmelund, Tor and Seger, Brian and Kuno, Masaru and Kamat, Prashant V.},

  abstractNote = {The halide ion mobility in mixed halide perovskite demonstrates two opposite trends in response to photo and thermal activation. While halides prefer to remain as Br-rich and I-rich domains under steady-state light irradiation of MAPbBr1.5I1.5 films, they prefer to remain in their stable mixed composition when kept in the dark. The activation energies as determined from the temperature-dependent rate constants are Ea,forward = 28.9 kJ mol–1 for photoinduced segregation and Ea,reverse = 53.5 kJ mol–1 for remixing of halides in the dark, respectively. The energy input from photoexcitation assists overcoming the dark (thermally activated) mixing to induce Br-rich and I-rich domains. This segregated state is maintained as long as the mixed halide film is irradiated continuously with visible light. The excitation intensity threshold above which segregation occurs follows a linear temperature dependence, such that phase separation occurs above Iexc = 30 μW/cm2 white light at 23 °C. The threshold at 90 °C becomes higher with a minimum intensity requirement of 100 μW/cm2 to induce segregation. The thermodynamic rationale behind this unusual halide mobility under photo and thermal excitation discussed here can aid in understanding the stability issues of perovskite solar cells.},

  doi          = {10.1021/acsenergylett.9b02265},

  journal      = {ACS Energy Letters},

  number       = 1,

  volume       = 5,

  place        = {United States},

  year         = {2019},

  month        = {11}

}

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