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

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 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.

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [3]
  1. Univ. of Notre Dame, IN (United States); Technical Univ. of Denmark, Lyngby (Denmark)
  2. Technical Univ. of Denmark, Lyngby (Denmark)
  3. Univ. of Notre Dame, IN (United States)
Publication Date:
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. https://doi.org/10.1021/acsenergylett.9b02265.
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
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.
@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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