Related Experiment Video
Updated: Jan 20, 2026
02:31
Phase Transitions and Effect of Intermolecular Forces
22.7K
Size-Dependent Phase Transition in Perovskite Nanocrystals
Lige Liu1,2, Ru Zhao3,4, Changtao Xiao3
1State Key Laboratory for Mesoscopic Physics, Collaborative Innovation Center of Quantum Matter, School of Physics , Peking University , Beijing 100871 , China.
The Journal of Physical Chemistry Letters
|August 30, 2019
Summary
Nanoscale methylammonium lead bromide (CH3NH3PbBr3) perovskite crystals exhibit size-dependent phase transitions. Smaller 2 nm nanocrystals lack the cubic-to-tetragonal transition observed in 4 nm particles, impacting their photoluminescence properties.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Halide and oxide perovskites possess complex structures influencing their physical properties.
- Nanoscale dimensions can significantly alter material behavior compared to bulk.
- Understanding size-dependent properties is crucial for designing advanced perovskite materials.
Purpose of the Study:
- To investigate the effect of reduced dimensions on the phase transition behavior of methylammonium lead bromide (CH3NH3PbBr3) nanocrystals.
- To correlate photoluminescence properties with phase transitions in single perovskite nanocrystals.
- To elucidate the size-dependent influence on temperature-induced phase transitions.
Main Methods:
- Single-dot optical experiments, including spectral and temporal photoluminescence probing.
- Investigation of methylammonium lead bromide (CH3NH3PbBr3) nanocrystals with average sizes of ~2 nm and ~4 nm.
- Application of Landau theory for theoretical calculations of phase transitions.
Main Results:
- Abrupt blue shifts in photoluminescence spectra and lifetimes at ~150 K were observed in 4 nm nanocrystals, linked to a cubic-to-tetragonal phase transition.
- This phase transition was absent in the smaller 2 nm nanocrystals within the studied temperature range (5-295 K).
- Theoretical calculations confirmed a strong size-dependent effect on temperature-induced phase transitions in individual CH3NH3PbBr3 nanocrystals.
Conclusions:
- The cubic-to-tetragonal phase transition in methylammonium lead bromide (CH3NH3PbBr3) is suppressed in ultrasmall nanocrystals (< 4 nm).
- Size-dependent phase transition behavior significantly impacts the photoluminescence properties of perovskite nanocrystals.
- Structure-property relationships in ultrasmall perovskite crystals must account for these size-dependent effects.
Related Concept Videos
02:31Phase Transitions
22.7K
Whether solid, liquid, or gas, a substance's state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the solid pack closely together, generally in a pattern. The particles vibrate about their fixed positions but do not move or squeeze past their neighbors. In liquids, although the particles are closely spaced, they are randomly arranged. The position of the particles are not fixed—that is, they are free to move past their neighbors to...
22.7K
02:33Phase Transitions: Sublimation and Deposition
19.7K
Some solids can transition directly into the gaseous state, bypassing the liquid state, via a process known as sublimation. At room temperature and standard pressure, a piece of dry ice (solid CO2) sublimes, appearing to gradually disappear without ever forming any liquid. Snow and ice sublimate at temperatures below the melting point of water, a slow process that may be accelerated by winds and the reduced atmospheric pressures at high altitudes. When solid iodine is warmed, the solid sublimes...
19.7K
02:39Phase Transitions: Melting and Freezing
14.6K
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
14.6K
02:39Phase Transitions: Vaporization and Condensation
20.7K
The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize (convert into vapor). The process is called vaporization—a surface phenomenon. Vaporization occurs when the thermal motion of the molecules overcome the intermolecular forces, and the molecules (at the surface) escape into the gaseous state. When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules...
20.7K
02:39Phase Diagrams
48.9K
A phase diagram combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. These diagrams indicate the physical states that exist under specific conditions of pressure and temperature and also provide the pressure dependence of the phase-transition temperatures (melting points, sublimation points, boiling points). Regions or areas labeled solid, liquid, and gas represent single phases, while lines or curves represent...
48.9K
05:15Flash Infrared Annealing for Perovskite Solar Cell Processing
8.6K
We describe a flash infrared annealing method used for the synthesis of perovskite and mesoscopic-TiO2 films. Annealing parameters are varied and optimized for processing on fluorine-doped tin oxide (FTO) glass and indium tin oxide-coated polyethylene terephthalate (ITO PET), subsequently giving devices power conversion efficiencies...
8.6K