Good Vibrations: Locking of Octahedral Tilting in Mixed-Cation Iodide Perovskites for Solar Cells

Dibyajyoti Ghosh, Philip Walsh Atkins, M. Saiful Islam, Alison B. Walker, Christopher Eames

Research output: Contribution to journalArticle

34 Citations (Scopus)
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Abstract

Metal halide perovskite solar cells have rapidly emerged as leading contenders in photovoltaic technology. Compositions with a mixture of cation species on the A-site show the best performance and have higher stability. However, the underlying fundamentals of such an enhancement are not fully understood. Here, we investigate the local structures and dynamics of mixed A-cation compositions. We show that substitution of low concentrations of smaller cations on the A-site in formamidimium lead iodide (CH(NH2)2PbI3) results in a global "locking" of the PbI6 octahedra tilting. In the locked structure the octahedra tilt at a larger angle but undergo a much reduced amplitude of rocking motion. A key impact of this feature is that the rotational or tumbling motion of the CH(NH2)2+ molecular ion in a locked cage is severely restricted. We discuss the impact of locking on the photovoltaic performance and stability.

Original languageEnglish
Pages (from-to)2424-2429
Number of pages6
JournalACS Energy Letters
Volume2
Issue number10
Early online date19 Sep 2017
DOIs
Publication statusPublished - 13 Oct 2017

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ASJC Scopus subject areas

  • Chemistry (miscellaneous)
  • Energy Engineering and Power Technology
  • Fuel Technology
  • Renewable Energy, Sustainability and the Environment
  • Materials Chemistry

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