Colloidal Organohalide Perovskite Nanoplatelets Exhibiting Quantum Confinement

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Colloidal perovskite nanocrystals have shown promising optoelectronic properties.
• Excitonic features in perovskite nanocrystals have been attributed to quantum confinement.
• Understanding the optical properties of low-dimensional perovskites is crucial for their application.

Purpose of the Study:

• To synthesize and characterize two-dimensional (2D) colloidal nanoplatelets of methylammonium lead bromide (MAPbBr3) perovskite.
• To compare the optical signatures of excitons in these 2D nanoplatelets with spherical nanocrystals and bulk MAPbBr3.
• To investigate the role of dimensionality on the optoelectronic properties of MAPbBr3.

Main Methods:

• Synthesis of colloidal nanoplatelets of methylammonium lead bromide (MAPbBr3) perovskite.
• Optical spectroscopy to analyze excitonic features.
• Purification techniques to isolate single unit cell thick nanoplatelets.

Main Results:

• Excitonic features previously attributed to quantum confinement in MAPbBr3 nanocrystals are properties of the bulk phase.
• Higher-energy absorption features originate from 2D nanoplatelets within the nanocrystal product.
• Purified colloidal nanoplatelets exhibit a sharp excitonic absorption feature 0.5 eV blue-shifted from bulk MAPbBr3.

Conclusions:

• Methylammonium lead bromide (MAPbBr3) perovskite can be synthesized as stable, single unit cell thick colloidal nanoplatelets.
• These 2D nanoplatelets possess distinct optical properties compared to bulk and spherical nanocrystals.
• This work expands the family of colloidal 2D nanostructures with unique optoelectronic characteristics.