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Title: Shift Happens. How Halide Ion Defects Influence Photoinduced Segregation in Mixed Halide Perovskites

Authors:
; ORCiD logo; ORCiD logo
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1361221
Grant/Contract Number:
FC02-04ER15533; SC0014334
Resource Type:
Journal Article: Published Article
Journal Name:
ACS Energy Letters
Additional Journal Information:
Related Information: CHORUS Timestamp: 2017-12-08 06:23:14; Journal ID: ISSN 2380-8195
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English

Citation Formats

Yoon, Seog Joon, Kuno, Masaru, and Kamat, Prashant V. Shift Happens. How Halide Ion Defects Influence Photoinduced Segregation in Mixed Halide Perovskites. United States: N. p., 2017. Web. doi:10.1021/acsenergylett.7b00357.
Yoon, Seog Joon, Kuno, Masaru, & Kamat, Prashant V. Shift Happens. How Halide Ion Defects Influence Photoinduced Segregation in Mixed Halide Perovskites. United States. doi:10.1021/acsenergylett.7b00357.
Yoon, Seog Joon, Kuno, Masaru, and Kamat, Prashant V. 2017. "Shift Happens. How Halide Ion Defects Influence Photoinduced Segregation in Mixed Halide Perovskites". United States. doi:10.1021/acsenergylett.7b00357.
@article{osti_1361221,
title = {Shift Happens. How Halide Ion Defects Influence Photoinduced Segregation in Mixed Halide Perovskites},
author = {Yoon, Seog Joon and Kuno, Masaru and Kamat, Prashant V.},
abstractNote = {},
doi = {10.1021/acsenergylett.7b00357},
journal = {ACS Energy Letters},
number = ,
volume = ,
place = {United States},
year = 2017,
month = 6
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1021/acsenergylett.7b00357

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  • Photoinduced segregation in mixed halide perovskites has a direct influence on decreasing the solar cell efficiency as segregated I-rich domains serve as charge recombination centers. Here, the changes in the external quantum efficiency mirror the spectral loss in the absorption; however, the time scale of the IPCE recovery in the dark is slower than the absorption recovery, showing the intricate nature of the photoinduced halide segregation and charge collection in solar cell devices.
  • Photoinduced segregation in mixed halide perovskites has a direct influence on decreasing the solar cell efficiency as segregated I-rich domains serve as charge recombination centers. Here, the changes in the external quantum efficiency mirror the spectral loss in the absorption; however, the time scale of the IPCE recovery in the dark is slower than the absorption recovery, showing the intricate nature of the photoinduced halide segregation and charge collection in solar cell devices.
  • Organolead mixed-halide perovskites such as CH 3NH 3PbX 3–aX' a (X, X' = I, Br, Cl) are interesting semiconductors because of their low cost, high photovoltaic power conversion efficiencies, enhanced moisture stability, and band gap tunability. Using a combination of optical absorption spectroscopy, powder X-ray diffraction (XRD), and, for the first time, 207Pb solid state nuclear magnetic resonance (ssNMR), we probe the extent of alloying and phase segregation in these materials. Because 207Pb ssNMR chemical shifts are highly sensitive to local coordination and electronic structure, and vary linearly with halogen electronegativity and band gap, this technique can provide the truemore » chemical speciation and composition of organolead mixed-halide perovskites. We specifically investigate samples made by three different preparative methods: solution phase synthesis, thermal annealing, and solid phase synthesis. 207Pb ssNMR reveals that nonstoichiometric dopants and semicrystalline phases are prevalent in samples made by solution phase synthesis. We show that these nanodomains are persistent after thermal annealing up to 200 °C. Further, a novel solid phase synthesis that starts from the parent, single-halide perovskites can suppress phase segregation but not the formation of dopants. Our observations are consistent with the presence of miscibility gaps and spontaneous spinodal decomposition of the mixed-halide perovskites at room temperature. This underscores how strongly different synthetic procedures impact the nanostructuring and composition of organolead halide perovskites. In conclusion, better optoelectronic properties and improved device stability and performance may be achieved through careful manipulation of the different phases and nanodomains present in these materials.« less
  • Hybrid halide perovskites such as methylammonium lead iodide (CH 3NH 3PbI 3) exhibit unusually low free-carrier concentrations despite being processed at low-temperatures from solution. We demonstrate, through quantum mechanical calculations, that an origin of this phenomenon is a prevalence of ionic over electronic disorder in stoichiometric materials. Schottky defect formation provides a mechanism to self-regulate the concentration of charge carriers through ionic compensation of charged point defects. The equilibrium charged vacancy concentration is predicted to exceed 0.4 % at room temperature. Furthermore, this behavior, which goes against established defect conventions for inorganic semiconductors, has implications for photovoltaic performance.