Entropy Stabilization Effects and Ion Migration in 3D “Hollow” Halide Perovskites
Journal Article
·
· Journal of the American Chemical Society
- Arizona State Univ., Tempe, AZ (United States); Northwestern University
- Northwestern Univ., Evanston, IL (United States); Univ. of South Florida, Tampa, FL (United States)
- Univ. of Bath (United Kingdom)
- Arizona State Univ., Tempe, AZ (United States)
- Northwestern Univ., Evanston, IL (United States)
- Univ. of Bath (United Kingdom); Univ. of Oxford (United Kingdom)
A recently discovered new family of 3D halide perovskites with the general formula (A)1–x(en)x(Pb)1–0.7x(X)3–0.4x (A = MA, FA; X = Br, I; MA = methylammonium, FA = formamidinium, en = ethylenediammonium) is referred to as “hollow” perovskites owing to extensive Pb and X vacancies created on incorporation of en cations in the 3D network. The “hollow” motif allows fine tuning of optical, electronic, and transport properties and bestowing good environmental stability proportional to en loading. To shed light on the origin of the apparent stability of these materials, we performed detailed thermochemical studies, using room temperature solution calorimetry combined with density functional theory simulations on three different families of “hollow” perovskites namely en/FAPbI3, en/MAPbI3, and en/FAPbBr3. We found that the bromide perovskites are more energetically stable compared to iodide perovskites in the FA-based hollow compounds, as shown by the measured enthalpies of formation and the calculated formation energies. The least stable FAPbI3 gains stability on incorporation of the en cation, whereas FAPbBr3 becomes less stable with en loading. This behavior is attributed to the difference in the 3D cage size in the bromide and iodide perovskites. Configurational entropy, which arises from randomly distributed cation and anion vacancies, plays a significant role in stabilizing these “hollow” perovskite structures despite small differences in their formation enthalpies. With the increased vacancy defect population, we have also examined halide ion migration in the FA-based “hollow” perovskites and found that the migration energy barriers become smaller with the increasing en content.
- Research Organization:
- Northwestern Univ., Evanston, IL (United States); Univ. of California, Santa Barbara, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC0012541; SC0021987
- OSTI ID:
- 1869303
- Alternate ID(s):
- OSTI ID: 1870313
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 18 Vol. 144; ISSN 0002-7863
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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