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Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films
Published on: September 8, 2017
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Methylammonium Cation Dynamics in Methylammonium Lead Halide Perovskites: A Solid-State NMR Perspective
Guy M Bernard1, Roderick E Wasylishen1, Christopher I Ratcliffe2
1Gunning-Lemieux Chemistry Centre, University of Alberta , 11227 Saskatchewan Drive NW, Edmonton, Alberta, Canada T6G 2G2.
The Journal of Physical Chemistry. A
|January 17, 2018
Summary
Methylammonium (MA) cations in lead halide perovskites exhibit rapid, continuous motion in the cubic phase. Subtle ordering emerges in the tetragonal phase, with dynamics freezing out in the orthorhombic phase.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Spectroscopy
Background:
- Methylammonium lead halides (CH3NH3PbX3) are crucial for photovoltaic applications.
- Understanding methylammonium (MA) cation dynamics is key to perovskite stability and performance.
Purpose of the Study:
- Reinvestigate MA cation dynamics in methylammonium lead halides (X = Cl, Br, I) across different temperature phases.
- Utilize advanced NMR spectroscopy to probe cation behavior and phase transitions.
Main Methods:
- Employed 2H, 14N, and 207Pb Nuclear Magnetic Resonance (NMR) spectroscopy.
- Analyzed temperature-dependent spectral data to determine cation dynamics and ordering.
Main Results:
- Observed pseudoisotropic tumbling of MA cations on a picosecond timescale in the cubic phase.
- Identified continuous dynamics across the cubic-tetragonal phase transition, with subtle MA ordering in the tetragonal phase.
- Demonstrated freezing of MA cation dynamics below the tetragonal-orthorhombic transition.
Conclusions:
- MA cation dynamics are highly temperature-dependent and influenced by crystal phase.
- A six-site model effectively describes MA cation ordering in the tetragonal phase.
- These findings provide insights into the structural and dynamic properties of perovskite materials for solar cells.
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