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Title: Improved phase stability of formamidinium lead triiodide perovskite by strain relaxation

Though formamidinium lead triiodide (FAPbI 3) 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 FAPbI 3-MABr) was found to cause lattice contraction, thereby balancing the lattice strain. This led to dramatic improvement in the stability of α-FAPbI 3. As a result, solar cells fabricated using FAPbI 3-MABr demonstrated significantly enhanced stability under the humid air.
 [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [1]
  1. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 2380-8195
Grant/Contract Number:
Accepted Manuscript
Journal Name:
ACS Energy Letters
Additional Journal Information:
Journal Volume: 1; Journal Issue: 5; Journal ID: ISSN 2380-8195
American Chemical Society (ACS)
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
Country of Publication:
United States
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; instability mechanisms; formamidinium lead triiodide perovskite; solar cells
OSTI Identifier: