Improved Phase Stability of Formamidinium Lead Triiodide Perovskite by Strain Relaxation

Xiaojia Zheng, Congcong Wu, Shikhar K. Jha, Zhen Li, Kai Zhu, Shashank Priya

Research output: Contribution to journalArticlepeer-review

364 Scopus citations


Though formamidinium lead triiodide (FAPbI3) possesses a suitable band gap and good thermal stability, the phase transition from the pure black perovskite phase (α-phase) to the undesirable yellow nonperovskite polymorph (δ-phase) at room temperature, especially under humid air, hinders its practical application. Here, we investigate the intrinsic instability mechanism of the α-phase at ambient temperature and demonstrate the existence of an anisotropic strained lattice in the (111) plane that drives phase transformation into the δ-phase. Methylammonium bromide (MABr) alloying (or FAPbI3-MABr) was found to cause lattice contraction, thereby balancing the lattice strain. This led to dramatic improvement in the stability of α-FAPbI3. Solar cells fabricated using FAPbI3-MABr demonstrated significantly enhanced stability under the humid air.

Original languageEnglish (US)
Pages (from-to)1014-1020
Number of pages7
JournalACS Energy Letters
Issue number5
StatePublished - Nov 11 2016

All Science Journal Classification (ASJC) codes

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


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