Triplet Energy Transfer from CsPbBr₃ Nanocrystals Enabled by Quantum Confinement

Area of Science:

• Materials Science
• Nanotechnology
• Photochemistry

Background:

• Lead halide perovskite nanocrystals (NCs) offer tunable spectral properties via size (quantum confinement) or composition. Compositional tuning through ion exchange is common, often overshadowing the role of quantum confinement.
• Polycyclic aromatic hydrocarbons (PAHs) are important molecules in various photochemical applications.

Purpose of the Study:

• To investigate the necessity of quantum confinement in perovskite NCs for efficient triplet energy transfer (TET) to PAHs.
• To elucidate the mechanism governing TET between perovskite NCs and PAHs.

Main Methods:

• Utilized static and transient spectroscopy on cesium lead bromide (CsPbBr3) NC-pyrene hybrids.
• Analyzed the influence of NC size, driving force, and spectral overlap on TET rates.
• Correlated TET rates with carrier probability density at the NC surface.

Main Results:

• Efficient TET was observed exclusively in small-sized, quantum-confined CsPbBr3 NCs.
• The size-dependent driving force and spectral overlap had minimal impact on the TET rate.
• TET rate showed a linear dependence on the carrier probability density at the NC surface, indicating a Dexter-type mechanism.

Conclusions:

• Quantum confinement is a critical factor for enabling efficient Dexter-type TET from perovskite NCs to PAHs.
• This energy transfer mechanism efficiently channels excitation energy into long-lived triplets in PAHs.
• The findings open avenues for applications in photon upconversion and photoredox catalysis.