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

367 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
Externally publishedYes

Bibliographical note

Funding Information:
The authors acknowledge financial support from the Institute of Critical Technology and Applied Science (ICTAS). S.P. and X.Z. would also like to acknowledge financial support from the Office of Naval Research through the MURI program. S.K.J. was supported through the Office of Naval Research participation in NSF I/UCRC: Center for Energy Harvesting Materials and Systems (CEHMS). The work at the National Renewable Energy Laboratory is supported by the U.S. Department of Energy under Contract No. DE-AC36-08-GO28308. K.Z. and Z.L. acknowledge support by the hybrid perovskite solar cell program of the National Center for Photovoltaics funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Solar Energy Technologies Office.

Publisher Copyright:
© 2016 American Chemical Society.


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