Hidden polymorphism of FAPbI3 discovered by Raman spectroscopy
Open Access
- 12 April 2021
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Physical Chemistry Chemical Physics
- Vol. 23 (15), 9476-9482
- https://doi.org/10.1039/d1cp00102g
Abstract
Formamidinium lead iodide (FAPbI3) can be used in its cubic, black form as a light absorber material in single-junction solar cells. It has a band-gap (1.5 eV) close to the maximum of the Shockley–Queisser limit, and reveals a high absorption coefficient. Its high thermal stability up to 320 °C has also a downside, which is the instability of the photo-active form at room temperature (RT). Thus, the black α-phase transforms at RT with time into a yellow non-photo-active δ-phase. The black phase can be recovered by annealing of the yellow state. In this work, a polymorphism of the α-phase at room temperature was found: as-synthesized (αi), degraded (αδ) and thermally recovered (αrec). They differ in the Raman spectra and PL signal, but not in the XRD patterns. Using temperature-dependent Raman spectroscopy, we identified a structural change in the αi-polymorph at ca. 110 °C. Above 110 °C, the FAPbI3 structure has undoubtedly cubic Pmm symmetry (high-temperature phase: αHT). Below that temperature, the αi-phase was suggested to have a distorted perovskite structure with Im symmetry. Thermally recovered FAPbI3 (αrec) also demonstrated the structural transition to αHT at the same temperature (ca. 110 °C) during its heating. The understanding of hybrid perovskites may bring additional assets in the development of new and stable structures.Funding Information
- Bundesministerium für Wirtschaft und Energie (0324095H)
- Deutscher Akademischer Austauschdienst (2017/91645541)
This publication has 26 references indexed in Scilit:
- Vibrational dynamics in lead halide hybrid perovskites investigated by Raman spectroscopyPhysical Chemistry Chemical Physics, 2020
- Temperature-Dependent Thermal Decomposition Pathway of Organic–Inorganic Halide Perovskite MaterialsChemistry of Materials, 2019
- Improved Phase Stability of Formamidinium Lead Triiodide Perovskite by Strain RelaxationACS Energy Letters, 2016
- Dynamic disorder, phonon lifetimes, and the assignment of modes to the vibrational spectra of methylammonium lead halide perovskitesPhysical Chemistry Chemical Physics, 2016
- Single Crystal Formamidinium Lead Iodide (FAPbI3): Insight into the Structural, Optical, and Electrical PropertiesAdvanced Materials, 2016
- Retrograde solubility of formamidinium and methylammonium lead halide perovskites enabling rapid single crystal growthChemical Communications, 2015
- Mixed‐Organic‐Cation Perovskite Photovoltaics for Enhanced Solar‐Light HarvestingAngewandte Chemie, 2014
- NH2CH═NH2PbI3: An Alternative Organolead Iodide Perovskite Sensitizer for Mesoscopic Solar CellsChemistry of Materials, 2014
- Semiconducting Tin and Lead Iodide Perovskites with Organic Cations: Phase Transitions, High Mobilities, and Near-Infrared Photoluminescent PropertiesInorganic Chemistry, 2013
- Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic CellsJournal of the American Chemical Society, 2009