Halide-Exchange Arrest Enables Reabsorption-Free CsPbCl₃/CsPbI₃ Perovskite Core/Shell Nanocrystals

Area of Science:

• Materials Science
• Nanotechnology
• Quantum Dot Research

Background:

• Expanding Stokes shift in perovskite nanocrystals (NCs) is challenging.
• High halide mobility in NCs hinders stable core/shell formation.
• Existing methods struggle to balance large Stokes shift with sharp, fast emission.

Purpose of the Study:

• To develop a method for achieving a large Stokes shift in perovskite NCs.
• To create stable core/shell perovskite NCs with suppressed reabsorption.
• To enable new applications in photonic and quantum technologies.

Main Methods:

• Applying a CdCl2 passivation step to CsPbCl3 NCs before halide exchange.
• Utilizing halide exchange to create CsPbCl3/CsPbI3 core/shell NCs.
• Employing transient absorption spectroscopy and DFT modeling.

Main Results:

• Achieved a ≈1.2 eV apparent Stokes shift with CsPbCl3/CsPbI3 core/shell NCs.
• Demonstrated ≈70% photoluminescence quantum yield and fast emission lifetime (≈10 ns).
• Confirmed suppression of reabsorption losses and ultrafast core-to-shell exciton transfer (≈60 ps).

Conclusions:

• CdCl2 passivation effectively blocks halide diffusion, enabling stable core/shell structures.
• This solution-processed chemistry allows heterostructuring-based wavefunction engineering in perovskite NCs.
• The developed perovskite NCs offer a practical route to reabsorption-free emitters for advanced technologies.